Coastal Sediments 2023

The following sections are included:

• FOREWORD
• CONTENTS

Decadal to centennial variations in sediment availability are a primary driver of coastal change within barrier systems. Models help explore how barrier morphology relates to past changes in magnitude of sediment availability, but this requires insights and validation from field efforts. In this study, we investigate the progradation of Anclote Key via its morphostratigraphy, a presently dynamic barrier on the Central Florida Gulf Coast. The results of our field efforts, including vibracores, ground-penetrating radar scans, and optically stimulated luminescence dating of sediments, reveal that Anclote Key has gone through at least two phases of sustained island-scale progradation, with an intervening episode of transgression followed by relative stability. We show that these shifts were likely driven by relatively small changes in shoreface sediment availability owing to the island’s limited accommodation and suggest that Anclote Key may have been relatively isolated from the alongshore sediment supply of nearby barriers prior to the late 20^th century.

The impact of storms on barrier islands can be predicted with increasing accuracy due to the development of process-based models and the use of high-resolution datasets. However, data availability is restricted in space and time, and the potential use of hydrodynamic forcing from global wave reanalyses and topobathymetric grids from global digital elevation models has yet to be comprehensively evaluated. In this paper, we seek to use global models to overcome the high cost and limited coverage of high-resolution topographic data while mitigating their own uncertainty. Here, coarse-resolution boundary conditions and grids from global datasets were used to model the impact of a 50-year return period synthetic storm on a dissipative barrier island using SWAN and XBeach. The runs with global models were compared to a baseline run with high-resolution data, with results indicating an overall underestimation in storm impacts for the global model runs. However, the erosional response to the synthetic storm is reproduced appropriately and erosion metrics are consistent with the baseline run, providing encouraging results for storm impact modelling with global datasets.

We analyzed elevation changes at the northern Chandeleur Islands, Louisiana, to quantify sediment fluxes and assess sediment transport processes over two time periods (1920 – 2007 and 2007 – 2015). Wave-driven alongshore sediment transport is the predominant fair-weather process, whereas storms transport sediment across the island platform and promote shoreline retreat. Major storm impacts, where storm surge exceeds island elevation, severely erode the island platform and remove sediment from the system. During periods of recovery, onshore bar migration and welding contribute to subaerial island growth. The analyses show changes in dominant transport processes type and dominance relative to storm response over the two time periods. These results provide understanding on the sediment transport processes that drive the geomorphic evolution of barrier islands which is crucial for predicting future resilience.

Arctic barrier islands and spits are dynamic features influenced by a variety of oceanographic, geologic, and environmental factors. Many serve as habitat and protection for native species and shelter the coast from waves and storms that can flood and erode the adjacent mainland. This paper summarizes results of a study documenting changes to barrier morphology along the North Slope coast of Alaska between the United States-Canadian border and Cape Beaufort, from 1947 to 2020. Changes considered include number of barriers, area and perimeter, shoreline length, barrier sinuosity and width, presence and number of relict terminus features, presence and coverage of tundra vegetation, barrier orientation, termini migration rates, and elevation metrics. Wave conditions are also summarized and related to changes in barrier morphology. The results of this study help to better predict future barrier evolution and prevalence along Alaska’s coast by increasing our understanding of Arctic barrier development, migration, and degradation via the evaluation of historical morphometrics.

Storm-induced erosion and shoreline retreat of barrier islands are assumed to be primarily controlled by the intensity of the hydrodynamic forcing and barrier morphology. However, less studied non-dynamic variables such as the underlying bedrock topography can mediate the morphological response in geologically controlled barrier systems. This work investigates the role of geological control on barrier island morphodynamics during an extreme storm event. Exposed to highly energetic wave conditions in the West of Scotland, a unique barrier island system developed over a gentle sloping bedrock surface along the Outer Hebrides. Morphological changes driven by an extreme storm in February 2022 were monitored along sections of the Hebridean barriers, revealing muted morphological storm response, but with alongshore variable storm impacts. These ranged from minor dune erosion to overwash of low-lying composite barriers and are linked to variation in barrier morphology and the slope of the bedrock-controlled shoreface and intertidal terrace, which strongly influence nearshore wave transformation. Results suggest that severe storm impacts in the Outer Hebrides barrier islands are only observed when there is an exceptional combination of hydrodynamic forcing (extreme storm waves with high tides and storm surges) and will be enhanced in areas with lower dune morphology and narrower geologically controlled intertidal terraces. Nearshore hydrodynamic processes such as surf beat and wave setup are likely to be important to understand morphological changes in such underreported geologically controlled barrier systems.

The gap between coastal change data collected at event to seasonal time-scales (e.g., storm events or annual surveys) and decadal to geologic time-scales (e.g., coring and geologic mapping) presents a distinct challenge to predictions of mesoscale (interannual to decadal) behavior. Yet, it is such mesoscale processes that shape coastal areas and resilience pathways on coastal management time-scales, including the expected project lifetimes of coastal engineering structures. Mesoscale coastal data is therefore critical to inform models and coastal management decisions. In order to help address this knowledge gap, we report here the results of analysis of interannual to decadal trends in shoreline change and the associated wave conditions at Fishing Point, Assateague Island, Virginia, USA. Shoreline change results suggest that the rapid growth of the western spit of Fishing Point led to a movement of the depocenter from the western spit to the southern tip of Fishing Point circa 2000. The southern tip began to sequester much of the sediment that had previously been feeding the western spit, leading to the near-complete erosion of the western spit and the rapid accretion of the southern tip. Results of the analysis of shoreline change as related to wave climate suggest that shoreline changes on interannual to decadal timescales are driven largely by fair weather wave climate, with potential additional inputs from storm-related transport. These findings demonstrate the significance of interannual to decadal processes on dynamic barrier spit coastlines and the importance of monitoring and understanding such mesoscale processes for improved coastal management decisions.

Tidal inlets are expected to expand as sea-level rise accelerates, and, in extreme cases, might fully drown barrier islands. Here we report on field observations and model predictions of tidal inlet expansion. Field observations show that many inlets globally have expanded beyond their equilibrium width, and that inlets now occupy 16% of global barrier islands. With a numerical model (BRIE-D), we have simulated barrier island response to sea-level rise, and found that most of the inlet expansion is from barrier island sediment deficits rather than tidal prism expansion. These results aid in the validation of barrier drowning against observations.

Communities residing on barrier islands depend upon the ability of barriers to withstand forcings such as waves, sea-level rise, and storms, particularly under stresses from climate change. Using a barrier island evolution model, we compare barrier response to linear versus accelerating sea-level rise. Results suggest that barriers are more likely to drown under accelerating rather than linear sea-level rise. The dominant style of barrier drowning also shifts from width drowning to height drowning. When our model of barrier evolution is coupled with a myopic economic decision-making model for beach nourishment and managed retreat, the general coastal management behavior is unchanged. However, the timing and position at which interventions are made differ. Therefore, decisions based on the assumption of constant sea-level rise rates rather than increasing rates may result in actions that are detrimental to communities and potentially reduce the barrier’s ability to maintain its subaerial landform.

Patterns of spit growth (elongation or re-orientation) can be sensitive to long-term changes in wave climate, which can starve downdrift barriers of sediment. This study quantifies sediment-bypassing processes and volumes at Chincoteague Inlet (Virginia, USA) under varying wave conditions through coupling the SWAN wave model with the flow and sediment transport module within the Delft3D modeling suite. Model results show that updrift spit elongation and re-orientation reduces the sediment volume delivered to the spit terminus by twelve-fold (from 69.7 to 5.8 ×10³ m³), whereas the sediment fluxes that bypassed Chincoteague Inlet were reduced by only a factor of three (from 60 to 20 × 10³ m³). This confirms our hypothesis that the spit re-orientation and elongation causes significant reduction of downdrift longshore fluxes toward the inlet and is likely responsible for inlet widening. Finally, it demonstrates that sediment bypassing is de-coupled from spit elongation and re-orientation processes. Such insights are critical to developing a regional sediment management plan.

On the decadal time scale coastal planning and management scale of relative sea rise level is usually considered as a trend or constant rate in rather than a dynamic, time varying influence on coastal change. However, coastal ocean sea level of along the east Florida coast and coastal regions further north is, to a first order, is controlled at the interannual and decadal time scale by the dynamics of North Atlantic circulation and Gulf Stream flow. This paper addresses the influence of Florida coastal ocean sea level oscillations on shoreface sediment volume, coastal sediment budgets, and potential for coastal transgression at the decadal time scale. The observed relation between volume changes of the shoreface sediment reservoir and sea level changes at interannual to decadal time scales opens the door to more refined predictions of coastal response at shorter time scales. There is a potential for coupling numerical modeling and machine learning methods to forecast the state of coastal morphology. To accomplish forecasting of coastal change based on rapid sea level oscillations, data sets similar to those described in this paper must be available for coastal areas threatened by ongoing rapid sea level rise and transgression. Vulnerability to inundation and transgression rates of coastal sedimentary environments could be determined at the interannual to decadal time scale with a good degree of accuracy.

Combining hard and soft costal protection solutions can be an appropriate measure to enhance structure lifetime. This study aims to quantify the morphological evolution of the nourished stretch and adjacent coastlines. A small-scale beach nourishment has been performed in front of a rock revetment at site in Faxe Ladeplads in Zealand, Denmark. The overall objective is to learn more about the dynamics of small-scale nourishments in low energy environments. Monitoring techniques include repeated topographic (Trimble RTK-GPS, drone surveying) and bathymetric (single beam) measurements. To measure the hydrodynamic conditions two surface acceleration buoys deployed at -4 and -7 m water depth were used. Sediment volumes from nourishments of size 70,000 m³ and 20,000 m³ redistributed relatively quickly. The nourished material built up the cross-shore profile and a longshore bar in this area, and distributed sediments in the direction of the dominant littoral drift (SW). Results suggest that the morphological evolution of the nourishment is dependent on local hydrodynamic conditions and local geomorphology. These findings have implications for the main objectives of preventing wave overtopping onto an adjacent coastal road during extreme events and restoring a beach for recreation.

Sagaponack and Bridgehampton occupy ∼9 kilometers (km) of ocean-facing beach along the south shore of Long Island, NY USA. This paper contextualizes the morphological changes of local beach nourishments within the long-term sediment management plan for these beaches. While there have been multiple engineering efforts to stabilize beach erosion along these sites, the largest occurred in 2013-2014 with the placement of ∼1 million m³ of beach quality sand via dredge. This project took place on the heels of Hurricane Sandy’s devastating impacts on the region and appears to have benefitted from such timing. From 2014 to 2019, the project area did not lose any appreciable amount of nourishment sand. However, from 2019 to 2021, the project area lost nearly 40 percent of the nourishment volume. These changes are related to post-storm changes as well as the adopted local depth of closure (DOC). These findings regarding the appropriate usage of DOC has implications on the application of a verified long-term sediment management plan with periodic maintenance projects for the Sagaponack and Bridgehampton BECDs.

Beach nourishment causes abrupt manmade changes to beaches that alter them from their equilibrium state. While beach nourishment is effective in increasing the size of beaches and their ability to protect nearby communities from waves and storms, the effects of beach nourishment on surf breaks is less well known. A five month study of a US Army Corps of Engineers beach nourishment project in Long Branch, New Jersey was completed to develop a greater understanding of the beach nourishment’s effects on surfing within the nourished area and at neighboring surf breaks. Surfability was studied at a nourished beach and an un-nourished beach to compare the effects of beach nourishment on surfing conditions. Surfability decreased in the short term, but started to return to the pre-nourished condition around three months post nourishment, likely due to many large wave events in the months post-nourishment. These findings suggest that appropriate timing of nourishment is important to consider for managing side-effects.

In the last several decades, beach nourishment has been a dominant strategy for coastal preservation to mitigate adverse impacts of erosion in the United States. Beach nourishment is a soft engineering activity to preserve beaches, reduce storm impacts and coastal flooding, provide habitat, support the economy, and improve the recreational value of beaches. It is expected that trends of beach nourishment are influenced by various natural (e.g., hurricane, tropical storms, relative sea level rise) and anthropogenic activities (e.g., inlet stabilization, policies). The objective of this study was to explore potential influences on beach nourishment trends in the top 10 coastal states with the highest nourishment projects and evaluate the long-term role of regional sediment management (RSM) on nourishment needs. The goal of this study is to help reduce planning and implementation costs, improve best management practices, and provide a methodological template for various stakeholders to implement analyses at their own scale of interest. It is found that erosion caused by increasing hurricane/tropical storms and sea level rise are the primary drivers for beach nourishment activities in certain state. The volume of sediments placed in states like FL Atl., NC, SC, and NY were likely driven by storm impacts. However, Texas and FL. Gulf did not show nourishment activities corresponding to the frequency of tropical storms and hurricanes. TX has a higher sea level rise rate compared to the any other state, which may have contributed to the state’s status in the top ten for nourishment. Higher number of inlets correspond with higher RSM projects in CA, MA, and NC. However, FL and NJ had less RSM projects despite the presence of numerous inlets. The statistical analysis executed for the Florida Atl. coast as proof of concept suggested that only tropical storms and SLR were statistically influencing the BN trends. The statistical significance of anthropogenic activities (no. of inlets) will be taken into consideration for future study.

A mixed sand and gravel beach 130 m in length is designed within the Bremerton Naval Complex, located along the northern shoreline of Sinclair Inlet in Bremerton, WA. The objectives of the design are to create a beach that will function as improved habitat specifically for fish forage and control erosion of the existing beach and backshore by maintaining the morphology and material type of natural, functioning Sinclair Inlet beaches. A spectral wave model developed for the site. Then longshore transport rates were estimated using the semi-empirical formula for gavel beaches, and cross-shore profile changes were calculated using coupled alongshore and cross-shore transport equations to design required mixed sand and gravel beach and feeder berm size to be placed on the updrift side. The beach was designed to mimic the beach slopes and materials of Sinclair Inlet shoreline. Construction monitoring will be ensured the intent of the design is implemented. These results suggest that the mimic design can protect against erosion due to wave attack and groundwater contamination of surface beach material during an extreme event.

This study proposes factors for designing the most optimal nourished profile without sand loss, ensuring practicality. In addition, by considering these factors, the study will provide sand volumes needed to conduct beach nourishment. The four proposed factors for beach nourishment include berm heights, widths of beach nourishment, foreshore slope and nearshore slope. Each factors can be calculated referring to studies conducted by many researchers. In addition, this paper presents the representative studies that can estimate the values. In addition, using previous studies, each optimal value was estimated and applied to Kkotji Beach and Haeundae Beach, which are representative of East and West Sea of South Korea. In the future, studies should be conducted not only for designing nourished beach profiles and planar layouts. These findings offer insights on better management of the usage of constrained sediment budgets for beach nourishments.

Artificial nourishments have become one of the main coastal erosion mitigation measures. The performance and longevity of the intervention is dependent on the sediment dynamics at the placement site. As the sediment deposition changes the bathymetry of the deposition area questions arise concerning the effects of the nourishments in the vicinity of the placement site. This study presents an analysis of the potential effects of the nourishments on the longshore sediment transport patterns and consequent impacts on the shoreline, at the vicinity of the deposition area. The study was performed through the application of CERC (1984) formula and the numerical model LTC (Coelho, 2005). To this end, based on CERC formula, it was identified the relationship between wave direction and shoreline orientation that leads to erosion or accretion effects in the vicinity of the nourishment. LTC numerical model was applied to discuss the evolution of the longshore sediment transport in nine sections located in the vicinity of the intervention. The numerical model results corroborate the importance of the relationship between wave direction and shoreline orientation. Generically, the cross-shore sections experience different sediments balances in function of their position in relation to the nourishment, being also affected by the wave direction. Overall, the findings show that the nourishments change the bathymetry in the placement site with impact on the shoreline orientation and consequent longshore sediment transport capacity. Therefore, the sediment transport that occurs after a nourishment is dependent on the relationship between waves direction and shoreline orientation.

Three cycles of beach nourishment at two barrier islands: Sand Key and Treasure Island, were studied over 17 years. Seventy-four and 17 beach profiles spaced ∼300 m apart were surveyed bimonthly to quarterly on Sand Key and Treasure Island, respectively. Six beach sections were distinguished based on beach dynamics, including 2 erosional hotspots, 1 gap in the nourishment and 3 typical erosive beaches. At most locations, the shoreline (defined at +1 m contour) returned to a similar location at the end of each cycle, indicating the nourishment successfully maintained the target beach width. The Treasure Island erosion hotspot experienced increased beach loss over time, suggesting that the current nourishment design may not be adequate. The gap in the nourishment did not experience significant sand gain on the dry beach. A mechanism to impound sand on the dry beach is necessary. The current nourishment successfully compensated the sand deficit. The mechanism causing sand deficit was not eliminated at all the sites, suggesting that the current nourishment design serves as a long-term maintenance strategy.

Florida beaches host some of the largest nesting aggregations for loggerhead sea turtles, with an average of ∼28,000 loggerhead nests per year in Palm Beach County alone in the past three years (2019-2021). Loss of sediment from coastal systems is resulting in significant beach erosion and threatening sea turtle habitat. The objective of this study was to evaluate natural and anthropogenic influences on beach geomorphology and sedimentology in relation to sea turtle reproduction efforts over a three-year period in Palm Beach County. Sediment was coarsest adjacent to Jupiter Inlet, where beneficial use of dredge material is frequently placed. Although different borrow sources were used for beach and dune restoration projects from 2019-2021, mean grain size, sediment sorting, and morphology were not found to influence loggerhead sea turtle reproduction efforts. Beach width and elevation changes occurred throughout the study period but did not have corresponding changes in loggerhead sea turtle nesting, hatching, or emergence success. Sediment varied from coarsest at R13A (inlet dredge material), to moderately sorted to moderately well sorted medium sand at R24 (upland mine source) and R41 (non-nourished), and to moderately sorted to moderately well sorted coarse sand at R31 (offshore borrow source). Most variability in sediment texture was measured at locations that use upland mined material and offshore borrow material. No trends were found between sediment characteristics or beach morphology and an influence on sea turtle nesting, hatching, or emergence success.

Carteret County, the Carteret County Beach Commission, and the Shore Protection Office (SPO) seek to provide long-term, sustaining management of Bogue Banks beaches. Carteret County intends to maintain Bogue Banks beaches via implementation of a proposed Master Beach Nourishment Plan (MBNP) with guidance from the SPO and oversight by the Beach Commission. The proposed program incorporates actions within multiple oceanfront municipalities to nourish recipient beaches, via use of multiple sand sources, over a multi-decadal timeline with revolving nourishment-project events. The proposed program incorporates actions within multiple oceanfront municipalities to nourish recipient beaches, via use of multiple sand sources, over a multi-decadal timeline with revolving nourishment-project events. Therefore, based on the above analyses, the preferred alternative for the Master Plan was determined to be Beach Nourishment with Non-structural Inlet Management. This is the only option that provides adequate sand sources to provide and maintain a 25-yr event level of protection for all of Bogue Banks as well as provide adequate infrastructure and habitat protection along the Bogue Inlet shoulders.

This paper summarises the available information on the Gold Coast beach nourishments for a period of over 40 years and compares recent small and large-scale nourishments that placed the sand in different parts of the beach profile. To date, around 25 Mm³ of sand has been used to nourish the Gold Coast beaches. The source is mainly from estuaries and artificial bypassing systems followed by offshore sand reserves and building sites. Placements vary significantly, example: small annual placement from creeks maintenance dredging, ad-hoc small nourishment from building sites; large and continuous permanent entrance bypassing systems; small and targeted upper beach and spit reconstructions; large and targeted such as the large-scale nourishment of 2017. Placement of the sand also varies from campaign to campaign from the dune, through to upper beach and nearshore areas and combinations of these. The Gold Coast is, therefore, a unique study case with several different strategies in place. This brings a significant amount of knowledge on placement performance and how they behave and disperse under a variety of conditions and locations. The compilation of past nourishments, their outcomes and their performance seeks to inform future works to allow the continuation of the proactive coastal management and protect it against extreme events and a changing climate.

An emulator capable of rapid prediction of the sub-aerial beach response to storm waves and water levels is used in this effort to assess the impact of morphological features on erosion volume. The unique emulator enables prediction of beach response considering a real cross-shore profile, as opposed to simplified approximations such as beach slope or width, such that the effect of a wide range of morphological features can be assessed. In particular, the location of the offshore sandbar and the presence of a berm on the beach are both shown to significantly affect the beach response. The location of the sandbar can reduce the erosional response to the same offshore wave energy by more than 3x, suggesting coastal hazard frameworks could provided improved warning and predictions by considering the state of the subaqueous morphology.

Morphological changes on wave-dominated beaches are challenging to address as they cover a wide range of spatial and temporal scales. Beaches in Lesser Antilles are well known to undergo brutal coastal erosion during energetic wave events, which are typically generated by hurricanes. While short time scale shoreline variability were often mentioned for those areas, other modes of shoreline response have been rarely studied. In this paper, we describe the shoreline dynamics at two study sites in Martinique with the use of smartphone-based cameras. These findings highlight the different and contrasted shoreline dynamics in Martinique that are likely to occur elsewhere in Lesser Antilles. On the west coast, at Le Carbet beach, we observed a significant seasonal behavior resulting in beach rotation, correlated with seasonal changes in wave direction. On the east coast, the data presented illustrate a shoreline-sandbar coupling mechanism, depending of the incident wave conditions. In this context, it can be hazardous to infer future shoreline position for those areas without a solid database of beach morphology or the knowledge of the dominant mode of shoreline variability. For these territories, where still few quantitative information is available on shoreline dynamics, the establishment of local coastal monitoring network is becoming essential. These preliminary observations in Martinique will be pursued but can already illustrate that smartphone-based cameras can significantly improve our understanding on beach morphodynamic.

In the present study, we evaluate the temporal variability in runup and total water level for sandy beaches along Cape Cod (Massachusetts, USA), and their impact on dune and beach erosion. We use a 43-year hindcast of waves and water levels and calculate runup and total water level based on the Stockdon formulation using previously extracted beach slopes. The dominant components of the runup are identified and their temporal variability evaluated. The seasonal and interannual variability of total water level is evaluated. For most locations along the outer Cape Cod coast, the comparison between total water level and dune elevations suggested that the coastal response remained predominantly under swash regime. The results over these study locations could be extended to other similar areas at regional scales to provide better characterization of total water level and coastal change at long temporal scales.

Beach evolution is important for the protection of coastal areas and the stability of ecosystems. The swash zone affects both the subaerial and subaqueous evolution of the beach. A properly practical prediction of the swash zone beach evolution is necessary for the evaluation of beach management scenarios. In this study, two practical swash sand transport models, i.e. the Larson (2004) sand transport formula and the Van Rijn (2009) distribution approach, were assessed. Model performance is quantitatively evaluated by comparing the predicted and measured profiles from large-scale wave flume tests. The calibrated Larson model can predict the beach accretion well while it shows weak performance for the erosive conditions. The Van Rijn distribution model is capable of predicting the shoreline retreat and progradation reasonably well but does not predict the profile evolution very well. Testing results indicate that existing practical swash sand transport models require further development and improvement.

Shoreline position varies over a wide range of temporal and spatial scales in response to a variety of processes. The monitoring of its position changes requires availability of high-frequency observations over a long period. In this study, the low-cost crowd-sourced system CoastSnap (Harley et al., 2019) is used to investigate the shoreline dynamics at the embayed beach of Lafitenia over a 9-months period. The high-frequency dataset, made up of 65 crowd-sourced images, was used to detect and to quantify shoreline changes at short time scales (from day to season). After the validation of CoastSnap images rectification thanks to in-situ surveyed data, a quantitative analysis of cross-shore position changes is undertaken using high tide waterline. Cross-shore dynamic of shoreline shows interesting patterns, with notable opposite movements of extremities. Despite some approximations, it is possible to obtain the shoreline position at a reasonable precision. The obtained results show apparent short time scale beach rotation for the first time at Lafitenia. This new shoreline mapping approach offers new perspectives to study short time coastal processes over long periods.

Accurate wave runup prediction on beaches is critical for coastal risk assessment and planning. Empirical wave runup parameterizations largely rely on offshore wave conditions and nearshore topography to characterize runup extent, neglecting any impacts associated with seepage processes and sediment properties. In this study, the numerical model SedOlaFlow is to investigate the impacts of sediment characteristics on wave runup under periodic waves. Sediment size (and therefore permeability) significantly impact runup extent and the interaction between successive swash excursions. Model results demonstrate that the maximum runup extent occurs after the fifth (second) wave for the sand (gravel) beach case. Saturation at the beachface from prior waves reduces turbulence and increases runup extent for the sand beach, a phenomenon not observed in the gravel beach. Ongoing work is aimed at implementing seepage and beach groundwater impacts into wave runup parameterizations.

The emergence of new techniques to detect shoreline change along sandy coastlines worldwide has meant that data-driven approaches to predict storm erosion are becoming increasingly feasible. This study explores how data-driven approaches can overcome the shortcomings of chained numerical models for swift application to sites with intermediate beach states of fluctuating energy. A large dataset of storm erosion derived from 276 individual storm events at the Narrabeen-Collaroy coastal monitoring site in SE Australia is presented. High-frequency shoreline data derived from a combination of in-situ and remote sensing methods (RTK-GPS, Lidar, Argus, satellite-derived and CoastSnap) are used to determine accurate measurements of beach width change for individual events over an 18-year monitoring period. A multi-linear regression model based on several key storm parameters (cumulative wave energy, average water-levels and wave direction) and beach conditions (prestorm beach width) is then tested. Results indicate that this model can predict storm erosion to a level of accuracy suitable for forecasting applications, paving the way for use in real-time coastal erosion early warning systems.

This paper uses analysis of run-up video images to assess the effectiveness of submerged breakwaters in erosion reduction via wave control. In order to examine the effect, an analysis was conducted at Bongpo Beach in Gangwon-do, South Korea, where three submerged breakwaters were installed. In this study, CCTV images taken at the time of Typhoon Maysak in 2020 were used. The image per second was geometrically corrected and the wave run-up distance was calculated through time-stack image analysis. As a result, it was confirmed that the run-up distance decreased in the rear part of the submerged breakwaters, and the standard deviation of the run-up distance was also analyzed.

The formation and evolution of sand ripples was investigated on a Gaussian-shaped sand mound under waves, currents, and combined wave-current conditions. Observations were collected in the Hydralab+ Total Environmental Simulator at the University of Hull as a part of the Morphological Diffusivity Experiment (MODEX) in the summer of 2018. Ripple geometry and migration were recorded using an underwater camera, LiDAR, and SONAR imaging. Mound diffusion was recorded under different combinations of waves and currents. Larger height and wavelength ripples formed when currents were dominant. Additionally, larger height and wavelength ripples formed at the crest of the mound compared with its base. Ripple steepness and asymmetry were also observed to be a function of wave-dominant or current-dominant conditions. Mound spreading was a function of both ripple migration and mound slope. These results on sand ripple characteristics have implications for understanding nearshore boundary hydrodynamics and morphodynamics.

Decadal time scale and high-resolution observational data on beach dynamics are rare. Here, we describe two of such data sets obtained from SW England and relate the seasonal variability in beach volume to wave forcing and north-Atlantic climate indices (NAO and WEPA). Perranporth, which is a representative sandy beach on the SW England north coast, experiences a unidirectional and strongly seasonal wave climate, which drives a dominantly cross-shore and seasonal beach signal. Slapton Sands, which is a representative gravel beach on the SW England south coast, experiences a bidirectional wave climate, which drives a dominantly rotational beach response caused by a longshore redistribution of sediment. Despite the contrasting coastal setting, wave climate and beach behavior, the morphodynamics on both beaches are strongly linked to Atlantic climate indices. Specifically, the most significant beach volumetric change occurred in winters associated with the largest values of NAO and WEPA. In addition to the strongly forced response, as testified by the link between beach change and wave conditions (and climate indices), beach response also depends strongly on the beach state/volume at the start of each season.

Here, high-resolution beach profiles, undertaken over the past 7.5 years, are employed to investigate sandbar migration on a micro-tidal sea-breeze dominated beach. Field observations reveal that onshore sandbar migration occurs during the winter storm season. On the other hand, sea-breezes are responsible of the offshore migration. Seasonal changes on the water levels seem to play an important role on sandbar dynamics in this region. The offshore (onshore) sandbar migration is correlated with beach recession (accretion) and hence plays an important role on the beach sediment budget. These findings provide understanding of the seasonal variability of sandbars along with its impact on the coastal protection they provide via wave dissipation and sediment input to the shoreface.

In this work, we conduct controlled experiments in a wave flume to represent different wave-wave interactions occurring in the swash zone. Using solitary waves as the forcing condition, we combined different wave amplitudes with separation times between the wave events. Experimental results show that interactions developing in the swash zone present three main stages: A jet slamming, an induced splash, and a region where the flow becomes fully 3D turbulent. We identified that the location where the interactions occur and the type of interaction depends on two main factors, the relationship between the wave amplitudes and the separation time between these wave events. Additionally, we were able to mimic the wave-wave interactions observed in real-case scenarios. Our goal is to relate these findings to the sediment transport processes in the swash zone, where interactions could develop a potential impact on the sediment transport mechanism and possible morphological changes.

In this study progradation of the dune toe on the sandy, dune-backed beaches of Makah Bay, on the Pacific Ocean shorelines of the reservation lands of the Makah Tribe, were documented for the first time. A shoreline assessment was implemented that included repeat beach profile surveys using RTK-DGPS and aerial lidar, and historical change analysis using aerial photos. Analysis of GNSS and aerial lidar suggest patterns of dune toe progradation over the last decade at average rates of~0.8 m/yr between 2010 and 2022 over almost all the 5.5 km length of beach in Makah Bay, excepting the ~250m long erosional area that prompted the study. A beach vegetation line delineated in aerial photos collected between 1952 and 2019 moved seaward at average rates of ~0.7 m/yr across the entire length of Makah Bay, suggesting that the pattern of progradation is long-lived. We assess evidence to evaluate whether this pattern of dune progradation can be explained by sediment supplies from watersheds draining to Makah Bay and conclude that local sediment supply cannot explain observed patterns. A variety of shoreline processes associated with relative sea-level fall are discussed and may explain the observed rates of shoreline progradation.

CSHORE, a one-dimensional process-based nearshore morphodynamic model, was able to simulate physically realistic sandbar dynamics over a 1-month time period for a dissipative, fine grained sandy beach in Oysterville, WA, USA. However, there are often limitations to calibrating models to barred beach profiles due to the penalization of spatially offset bar topography (i.e., phase shift). To assess these limitations, the Bayesian Generalized Likelihood Uncertainty Estimation (GLUE) method, which includes model calibration and uncertainty estimation, was applied to CSHORE model outputs. The results indicate that the modeler’s selection of error metric and evaluation domain influence the ranking of parameter sensitivity and the region of parameter space identified as skillful (i.e., optimal parameters). The corresponding bed elevation uncertainty intervals provide insights into error metric behavior and omitted relevant physical processes. These findings provide guidance for modeling best practices and highlight short-comings of current automated calibration routines on barred beaches.

Shoreline dynamic prediction remains a key issue worldwide and various approaches have been developed to address this issue. Among these approaches Artificial Neural Networks (ANN) allow considering many different parameters although they do not address the hydro-sedimentary processes. In the present work, use of ANN allow exploring a large number of morphological and hydrodynamic parameters in shoreline dynamics using three years of daily video extracted data. The field site is situated in a mesotidal environment and exhibits a strong seasonality in both hydrodynamic conditions and shoreline positions (up to 40m cross-shore migration). Preliminary results indicate that inclusion of the outer breakpoint position (a proxy of the outer bar location and the surf zone width) improves the performance of the predicted shoreline while inclusion of the tide parameter does not improve the prediction. These findings have implications for the development of ANNs on par with equilibrium-based models.

The U.S. Geological Survey (USGS) provides operational forecasts of total water levels (TWL) and coastal change. Uncertainties around forecast TWL are based on the temporal and spatial range of observed beach slopes near the forecast site. This paper investigates other sources of uncertainty that are not accounted for, focusing on four beaches where the USGS has deployed remote cameras, and on outer Cape Cod, which has diverse bar morphologies. We find that the range of runup indicated by ten formulae is nearly as large as the variations caused by the range of beach slopes. A formula that accounts for bar morphology substantially decreases calculated runup, and might improve forecasts. Errors in the timing of forecast storm landfall generate uncertainties in TWL where tides are large. Analyses suggest that the effect of off-normal incident waves is relatively small. These results suggest opportunities for improving the TWL forecasts.

In this research, we explore the role of the geological control along a beach located in the western side of Sardinia Island where biogenic carbonate sediment derived from coastal ecosystem represent an important fraction of the total sediment mass that compose the studied beach and dune system. A series of beach profiles were acquired to map the bathymetry of the submerged beach. Beach profiles were spaced about 25m apart and running from the toe of the dune, down to the depth of 6-8 meters. Subaerial beach profiles were acquired using the stop and go modality by a Digital Global Positioning System (DGPS). Submerged beach profiles were acquired coupling DGPS system with a single beam echo sounder (accuracy 10cm), using a small boat operating from the depth of 6-8 m up to the shoreline. A well pronounced E-W submerged channel located in the southern part of the beach was highlighted by the bathymetric survey. In correspondence of this channel, a large rip current was monitored by using a camera, during an intense mistral storm. The activity of this rip current may be responsible of the transferring of the sediment from the beachface and the foreshore to deeper depths. These results have implications on whether the presence of the seagrass Posidonia oceanica meadows can promote the production of biogenic carbonate sediment that can be delivered to starved coastal systems on the Mediterranean shoreline.

The combined effect of storm surge and large waves is the main driving mechanism that erodes beaches, inundates low-lying areas, leading to millions of dollars in property damage, loss of natural resources, and lives. The U.S. Geological Survey (USGS) aims to expand the real-time total water level (TWL) forecast provided in the Operational Total Water Level and Coastal Change Forecasts (TWL&CC) to the Great Lakes short- (0 – 36 hours) to medium-term (3 – 5 days) coastal-hazard forecasts to inform planners and emergency responders. This study assesses the skill of forecast water levels and wave characteristics required as input to the TWL forecasts. It finds that, while skill generally decreases as forecast period increases, these data are suitable as input to the TWL forecast system. As the TWL predictions depend on the water level and wave forecasts, validation against field observations allow evaluation of their suitability for the Great Lakes. These results have implications on the prediction of water levels and their potential impacts on coastal resiliency in North America.

The present study aims at presenting preliminary results on interaction between riprap and groundwater dynamics. Data were collected under moderate swell conditions (Hs∼1.5m and Tp∼15s) using pairs of pressure sensors attached at three sticks buried at three cross-shore location between the mean water level and the high tide level. For the 4 monitored tides, the pressure sensors showed a similar response with four different phases. During the first phase, prior to the low tide, no vertical pression gradient is observed, then during the second, then the tide starts to increase we observe a that exfiltration is taking place. Phase 3 is characterized by a brutal reverse between exfiltration and infiltration when the sea level reaches the elevation of the sensor consistent with previous studies. More surprising is the brutal reverse to exfiltration observed just before the high tide is reached. Observations must be completed by new data set to clarify the processes behind exfiltration phenomena. These findings have implications on the impact of hard structures on watertable elevation under specific conditions in their wide deployment along the world’s coastlines.

A combination of 1D models - Xbeach and Litpack (Litline) - were used to model the coastal morphodynamical changes in Brandon Bay on the west coast of Ireland. The models were simulated for a stormy period in February 2022. Model results are compared to survey data of 7 cross-section profiles along the sandy beach taken on 19^th and 25^th February 2022. The results show that both models can produce erosion and deposition rates in the same order of magnitude as the survey data. Furthermore, the model can also replicate the trends where the coastline and profiles on the east part of the bay show higher magnitude changes compared to the west. The use of the two different models can also complement each other, where Xbeach results provide changes in the cross-shore profiles, and Litline provides the changes in the coastline.

Louisiana’s land loss problem is a well-studied phenomenon. In order to mitigate the effects of this phenomenon, Louisiana Coastal Protection and Restoration Authority has set in place the Coastal Master Plan, with marsh creation projects as a cornerstone. Marsh creation projects are costly, mainly due to dredging costs. A better understanding of the dredging process and its driving factors can help reduce the costs. In this paper these factors are analyzed setting the basis for the future development of an empirical model. Three different projects, that had different locations, dredge fill material and equipment used were analyzed. It was possible to conclude that there is a correlation between sediment type and the bulking factor in the finished projects. The material used in each project depends on site availability, as well as the type of restoration project. Barrier island restoration projects tend to use coarser materials, whereas marsh restoration projects use finer sediments. The development of a model will use the data presented in this paper, as well as integrating other projects developed by CPRA to obtain a broader data set that provides more accurate results. The findings of this model could have implications on the economic value provided by the wetlands in the form of property protection, as even a small increase in the solid wetland to water ratio could yield significant monetary savings.

This work presents a sediment transport module validation of MUSTANG (MUd and Sand TrAnsport modelliNG) coupled to the three-dimensional hydrodynamic model CROCO (Coastal and Regional Ocean COmmunity model) code. The study area was located at the Northern Cotentin Peninsula located in Normandy (France). The 1DV multiclass laboratory flume test case implemented under CROCO/MUSTANG coupling aims to reproduce the one established by Olivier (2004). It is a 3 m long flume with a water height of 0.2 m with a water column divided into 20 equal-separated sigma layers where the mean velocity at depth is fixed at 0.58 m/s. This configuration includes a bottom layer composed of two siliceous sediments diameters: 600 μm and 255 μm with a density equals to 2800 kg/m3 and an initial respective distribution of 50%. Others studied cases reproductions will permit the model to become more and more realistic by considering non-cohesive, cohesive and heterogeneous mixture sediments, hiding and exposure process, etc.

Burial of pipe and cable lines in coastal waters via trenching operations is a common practice necessary to protect infrastructure. The objective of this analysis was to provide a comprehensive evaluation of short-term impacts caused during pipeline installation, assessed over a range of possible hydrodynamic conditions, by incorporating information on burial methods and local seabed properties into a sediment transport model which simulates construction activities as a moving mass source. This approach is applied to a case study which includes access dredging and trenching operations required for burial of a pipeline through distinct lagoon and offshore environments. Impacts of construction-induced sediment transport were evaluated in terms of extent of maximum Total Suspended Solids (TSS), duration above certain TSS thresholds, and total deposition. Model setup, sediment transport results, and variability over the considered range of environmental forcing conditions are discussed. These results could be used by decision makers to select a construction start month to minimize impacts. Although presented results are case study specific, this analysis framework could be applied, and expanded upon, to mitigate impacts of pipeline burial in any location with sufficient data.

The anticipated construction of the Liberty Development Island near Prudhoe Bay, Alaska, has created a need to understand how the island may influence sediment transport patterns and deposition on the nearby Boulder Patch ecosystem. This study uses a numerical model to characterize sediment transport pathways in Foggy Island Bay with and without the artificial island in place. We present the Delft3D-based model setup and application that yields an improved quantification and understanding of the region’s hydrodynamic, wave, and sediment transport patterns. The results for the present show mainly east-west directed, alongshore transport of silt and clay. Insertion of the planned island results in limited changes to the overall hydrodynamic and sediment transport patterns within the Bay but reverses erosional tendencies across a boulder patch, situated within a kilometer of the planned construction location, to being net depositional.

The BA-0203 Barataria Basin Ridge and Marsh Creation - Spanish Pass Increment is located close to the mouth of the Mississippi River, extending west from Venice, Louisiana. The specific goals of the project were to create/nourish approximately 622.4 hectares of brackish marsh and create 53.4 hectares of marsh ridge. Multiple borrow areas were developed, but the USACE and local river pilots expressed concerns with the preferred borrow area. Analytic and numerical analyses were performed to address these concerns. This paper discusses the modeling and observations following 75% completion of the project. The Spanish Pass project is approximately 75% complete. Several borrow areas were developed for the project with the contractor, Weeks Marine, electing to dredge the borrow area located closest to the eastern end of the fill area. Modeling was performed to ensure that dredging of the borrow area would not destabilize the Mississippi River navigation channel. Surveys of the navigation channel and borrow area suggest that the model findings were correct with no shifting of the river thalweg being observed. Infilling of the borrow area has been observed with over 1.4M m³ of infilling having occurred with removal of over 10.3M m³. The infilling rate was greatest when the Mississippi River stage was rising and abated when the Mississippi River stage dropped. Elevation of the fill area is critical for desired habitat creation. Geotechnical analyses were performed to estimate the settlement rate and fill elevations are following the expected settlement rate.

Kustvisie aims to develop a vision to maintain the current protection of the entire Belgian coast against flooding, also in future, up to 3m sea level rise. In this phase, all parties involved work together via ‘workbenches’ on the basis of the most recent scientific insights, their own research and their own wishes, to develop a strategic plan. This should become a roadmap with the socially most desirable measures to protect our coast against a 1000-year storm in the event of a sea level rise of up to 1, 2 and 3 meters. This paper presents Coastal Vision: a general overview of the process and study approach is given with a focus on how alternative solutions, including soft, hard, hybrid and nature based solutions, were assessed and optimised in order to identify the most desired future coastal protection strategy. Coastal Vision focused on adaptive coastal protection strategies in the long term for the Belgian coast, against higher and accelerated sea level rise. A wide range of solutions with corresponding space claims were investigated through a participatory approach. An assessment framework was applied to investigate with increasing detail throughout the project the different solutions. This outcome of this project has implications on coordination of resources to manage coastal protection in the face of future uncertainty.

This “proof of concept” analysis presents an updated examination of storminess along the U.S. eastern seaboard using significant wave height (wave power) and storm surge data from stations located on the extreme latitudinal ends of the coast. Storms were identified from those datasets using two previously published thresholds for each parameter. Additionally, the impact of successive ‘storm surge’ storms on beach erosion potential was evaluated using a cumulative storm impact index (CSII) model. Preliminary results show an increase in the number of ‘storm surge’ storms c. 1970 to the north and c. 2000 to the south with a corresponding cumulative impact on beaches at each location. No trends emerged from analysis of shorter-term wave power data. This paper also discusses obstacles to and important decision-making aspects of storm delineation studies.

Sea level rise is expected to affect coastal areas all around the world, including the estuarine environment. New bathymetry collected in 2014 provided a unique opportunity to test the modeling of Elmilady et al. (2019), who presented a morphodynamic DELFT3D model of San Pablo Bay, California, that included detailed tidal water movement, wind-wave action, sediment transport, and resulting bed level updates. Their hindcasts (1856–1983) showed significant skill in reproducing observed patterns and volumes of deposition and erosion in San Pablo Bay. Their forecasts (1983–2100) showed that sea level rise results in increased deposition, loss of intertidal flats because of drowning, and a greater channel volume. The model, in general, forecasted observed trends in change from 1983 to 2014. Morphodynamic modeling is a promising approach for identifying the effect of sea level rise on estuarine environments.

Barrier islands are susceptible to erosional hazards from hurricane-induced waves. As global warming will influence the future climate, it would affect the frequency and intensity of hurricanes, i.e., Hurricane Climatology Change (HCC). HCC will also be accompanied by Sea Level Rise (SLR), increasing the present-day shallow water depths, and permitting larger waves to reach the shoreline. Here, we develop and test a physics-based modeling approach to quantify the effects of HCC and SLR on erosional hazards to a beach-dune system on a New Jersey Barrier Island (NJBI). A calibrated XBeach-surfbeat model is used to simulate morphological changes generated by synthetic major hurricanes that represent climates of a historical period and a future period under the RCP8.5 scenario. Simulations are also performed under an SLR scenario for the future period. The results of the developed modeling approach successfully model the past increase in hurricane-induced coastal erosion to the beach-dune system in the study site, as well as forecasting a future increase.

The US Environmental Protection Agency (EPA) developed early scenarios of sea level rise (SLR) for Charleston, South Carolina, USA, using 1980 as the base year and projecting changes to 2025 and 2075 (Titus and Barth 1984). This paper compares the EPA projections with actual SLR forty years later and discusses observed physical changes to date in the study area. The Baseline condition projects the century historical trend (2.5 mm/yr) to a rise of 11.2 cm. Low, Medium, and High Scenarios under global warming at various rates projected SLR of 28.2 cm, 46 cm, and 63.8 cm. Actual SLR in Charleston from 1980 to 2000 was 16.5 cm or roughly 45% above the Baseline trend but only 60% of the Low Scenario projection. As a result, physical changes to the Charleston study area have been subtle for the most part, with notable exceptions. Nuisance flooding has increased significantly and has focused mitigation efforts on improving storm drainage. Major displacement or transformation of marsh habitats has not occurred, indicating sedimentation has generally kept pace with local SLR. At some sites near major inlets, sand bypassing has introduced massive quantities of sand and produced areas of new barrier beaches, lagoons, and marsh. The observed changes to date demonstrate that site-specific processes, such as sand bypassing, still dwarf the impacts of SLR on the coastal landscape. Coastal scientists, engineers, and managers must decide whether target shoreline positions can be maintained if recent accelerations in SLR continue.

Sea-level rise, increased coastal erosion and flooding due to climate change is threatening coastal communities across the world. Globally, coastal change management policies include zonation of the coast to restrict development in areas susceptible to coastal change. Defining the extent of the coastal change area can be problematic and is often done using large-scale (>1 km) coastal classifications and estimates of coastal retreat. In this study, we investigate the south west coast of England, using a high-resolution (0.1 km) coastal classification to determine coastal types and their response to sea-level rise. Nine coastal typologies were defined in the study area which covers >2000 km, with a further 41 sub-types. The main coastal types identified in this study are groups of sub-types. This variance in coastal types highlights the need for a mixed model approach for assessing shoreline change. Using this coastal typology, classification will allow coastal managers to apply relevant coastal change projections to identify areas where coastal change management and adaptation policies should be implemented.

Regional scale assessments of future chronic coastal hazard impacts are critical tools for adaptation planning under a changing climate. Probabilistic simulations of hazard impacts can improve these assessments by explicitly attempting to quantify uncertainty and by better simulating dependence between complex multivariate drivers of hazards. In this study, probabilistic future timeseries of total water levels (TWLs) are generated from a stochastic climate emulator (TESLA; Anderson et al., 2019) for the Cascadia region, USA for use in a chronic hazard impact assessment. This assessment focuses on three hazard metrics: collision, overtopping, and beach safety, and also introduces a novel hotspot indicator to identify areas that may experience dramatic changes in hazard impacts compared to present day conditions. Results are presented for a subset of the Cascadia region (Rockaway Beach Littoral Cell, Oregon) to demonstrate the power of the probabilistic impact assessment approach. The results highlight how useful spatially varying, scenario-based hazard impacts assessments and hotspot indicators are for identifying which areas and types of hazards may require increased adaptation support. This approach enables us to piece apart the relative uncertainty of hazards as driven by SLR versus natural variability (caused by variation in climate, weather, and hydrodynamic drivers).

Coastal dunes form the first line of defense against flooding and provide important ecological and socio-economic benefits to communities. Coastal dunes are expected to experience increased erosion with climate change and past dune dynamics can provide important insights into coastal resilience and inform predictions of future morphological changes. Here, dune dynamics for 39 sites in Cornwall, UK, are investigated using a 11 to 12 year airborne LiDAR dataset to characterize their dynamics and their exposure to storm waves. Half of the sites (20/39) are experiencing volume loss, dune retreat or both. Considering both volumetric changes and changes to the dune foot, 21% of the sites (8/39) are stable. The remaining 28% of the sites (11/39) are either accreting or prograding, or both. While dune loss/retreat is typically associated with storm wave action, neither the rate of volumetric change or rate of dune foot change correlate with long-term extreme wave statistics at the sites, indicating that other factors such as coincidence of storms with large tides and sediment availability are also key to decadal-scale dune evolution. Analyses of past shoreline change is important for understanding coastal change and inform future shoreline. Improving estimates of future shoreline change allows for more robust and informed coastal management decisions and thus more coastal resilient communities.

Coastal dunes represent natural barriers against coastal flooding and erosion, a better understanding of their dynamics is required in the context of sea level rise. This study explored, for the first time, the storm response and multi-annual recovery of coastal dunes at a continental scale. Using airborne LiDAR data at eight study sites spread along the Atlantic coast of Europe, this study examined dune response and recovery from a sequence of extreme storms. Results showed that dune scarping is strongly correlated to dune slope along relatively wide, exposed and dissipative beaches, while dune response along double-barred beaches shows smaller correlation with dune slope and large alongshore variability that are highlighted by the presence of large erosive megacusp embayments. Dune recovery was shown to be highly site specific and full recovery can cover years and could take decades at some of the study sites. The volumes of recovered sand within the six years following the extreme storms were not correlated to the volumes of sand lost during these storm events. The large diversity of coastal dunes along the Atlantic coast of Europe and the sequence of extreme storms observed during the 2013/14 winter, considered as the most energetic storms since at least 1948, represent a unique opportunity to study the spectrum of coastal dune response from extreme storms using airborne LiDAR data.

Here we modify an existing analytical model framework for simulating net volume changes to coastal foredunes resulting from the combination of wave-driven erosion and wind-driven accretion and apply it to investigate how dunes may response at multi-decadal timescales. A climate emulator is used to generate numerous possible future time series of waves, winds, and water levels of the Outer Banks, NC, USA coastline that are input to the model to predict dune volume changes. Expected timelines for net dune destruction, taking into account the net influence of sediment inputs and exports, are calculated from the ensemble outputs. Only 2% of the simulated cases result in dune destruction by 2050 for cases with a zero shoreline change rate (SCR). Cases with 1 m/yr SCR and 2 m/yr SCR result in net dune destruction in 14.2 yrs and 7.6 yrs, respectively, according to the model. These results therefore indicate the challenges in designing coastal foredunes to design every possibility of future oceanographic states, although this methodology could be used to optimize dune geometry for a specific dune design criteria.

Coastal sand dunes provide significant natural protection against coastal flooding. Understanding the physical drivers of dune erosion is therefore key to improve nature-based methods for coastal protection. This paper presents the results of controlled dune erosion experiments conducted in a wave flume, to examine the potential role of sand moisture content on dune erosion. Two moisture contents, representing a ‘dry’ and ‘wet’ dune (volumetric water content, VWC = 0.03-0.08 and VWC = 0.13-0.18, respectively) showed that dune pore-water content can influence the rate of dune erosion. The dune face consistently receded more rapidly for the higher moisture content cases. However, the final dune recession magnitude was observed to be independent of the initial sand moisture content and instead was a function of the vertical extent of wave runup relative to the dune face. These findings have implications for the understanding and prediction of dune erosion due to storm impacts for coastal engineers and managers.

Nowadays, it is common to find degraded coastal fringes which require constant sand nourishments. Due to human direct interventions increasing erosion patterns or because of climate change, these critical coastal zones need innovative solutions to reduce the amount of nourished sand and increase the duration of this actions to reduce its maintenance costs. This work presents two nourishment alternatives compared to a standard homogeneous nourishment and a no action scenario for a coastal degraded beach. Xbeach numerical model has been used to study the different planned scenarios when considering an energetic storm for one of the Catalan endangered coastal fringes in the Ebro Delta. The results of deploying the nourished sand by forming a single dune or a field of mound dunes are compared to a no-intervention scenario and the classical homogeneous nourishment, obtaining a theoretical relevant reduction of eroded sand when nourishing the beach building a unique coastal dune. This study is a simple exercise, with no validation of the obtained results and the known limitations of the numerical model employed, but valuable to see that different shapes and volumes of nourished sand can importantly increase/alter the duration of the new sand being provided to a vulnerable coastal fringe.

The U.S. Pacific Northwest (PWN) coastal dunes are mainly colonized by two non-native beachgrass species (i.e., Ammophila arenaria and A. breviligulata) and a native dune grass (Leymus mollis) that capture sand and build dunes of different morphology. Recently, a hybrid beachgrass was discovered with unknown consequences for dune evolution. We set up a common garden experiment including seven treatments and two control plots to understand the effect of native and non-native plant species on sand accretion and dune morphological evolution. After 1.6 years, sand volume increased the most in the non-native species plots with levels at least twice as high for A. arenaria as compared to the other plots. The hybrid species had moderate sand accretion but a survival rate of 1.4 and 2.1 times higher than its parent species and native species, respectively. These results provide new insights for U.S. PNW coastal dune management.

This contribution presents the response of experimental management methods implemented along 2 km stretch of the southwest coast of France with the objective to restore aeolian dynamics and foredune mobility to promote quasi alongshore-uniform landward foredune migration. The analysis based on eight airborne LiDAR campaigns and several morphometric indicators shows that the alongshore and temporal variability of foredune evolution depends on natural dynamics and contrasted managed strategies. These experiments offer new perspectives and guidelines for coastal dune managers in areas where chronic erosion threatens fixed dune systems.

Here, we present moisture content and sediment strength measurements measured in ten centimeter segments along a ∼ 85 cm high dune scarp profile at the Atlantic beach in Duck, North Carolina, USA in October 2020. The goal is to provide some initial geotechnical properties at different heights of a scarp found in the field. Initial field measurements including in-situ moisture contents and sediment strength were carried out on a ∼85 cm high vertical dune scarp at the sandy Atlantic beach just north of the town of Duck, North Carolina. Measurements were conducted after a period of “dry” days, i.e., with no inundation, limited contact of waves and the dune scarp, or rain events. The initial results highlight the complexity of the vertical structure of the scarp. Holes, likely from local fauna, as well as vegetation root mats affected moisture content and strength. For the “dry” conditions at the time of measurements, textural properties such as packing and bulk density appear to take a predominant role in governing sediment strength. However, this is expected to change during inundation, wave contact, or rainfall events when moisture contents are expected to increase, leading to a decrease of soil suction and apparent cohesion. These findings provide greater understanding of dune scarping, which represent significant erosion events which can weaken the dune integrity.

While it is recognized that moisture content plays an important role in dune-slope stability, particularly as associated with storms, there are limited quantitative measurements of internal moisture dynamics within the dune face. Here we present new data characterizing the internal horizontal, vertical, and temporal variability in dune moisture over a one-year period within a vegetated dune in Duck, North Carolina, USA. These data are related to dune stratigraphy, tides, groundwater levels, total-water levels, and precipitation to constrain the relative roles of these factors in controlling internal moisture patterns. Our results indicate that spatial and temporal patterns of internal dune moisture are driven by fluid infiltration in response to changing environmental variable(s), likely affecting the erosion potential of the dune. Complex wetting and drying patterns are also evident at the event timescale. Furthermore, there is strong seasonality in the total-moisture contents within dunes, an observation with important implications for “priming” of dunes for erosion.

Aeolian transport rates decreases during wet conditions as the threshold shear velocity for initiation of transport increases over moist sand. This study investigates the influence of surface moisture on meso-scale aeolian transport simulations. Yearly transport rates towards the dunes are simulated with ten different threshold-based models to account for moisture effects. The ten models show large variability when comparing the wet threshold shear velocities for a range of surface moisture conditions. However, for yearly simulations of aeolian transport towards the dunes, all models resulted in similar transport rates, which were considerably lower than simulations not accounting for moisture effects. The results suggest that in meso-scale aeolian sediment transport simulations, accurate predictions of surface moisture are more important than the selection of threshold-based models.

Coastal foredunes can mitigate the impacts of intensifying hurricanes and extratropical storms on vulnerable, low-lying communities. However, the degree of foredune resilience to climate change remains largely unquantified. Here, we use the numerical AeoLiS model to project annual-scale patterns of accretion and erosion of coastal foredunes for a range of beach and dune morphologies representative of the Outer Banks, North Carolina, USA. The model is subsequently used to explore how sea-level rise and changes in storminess may modify future dune volumes across beach morphologies. Model outcomes suggest that even modest rates of sea-level rise have the potential to greatly exacerbate dune erosion; whereas increased storminess may lead to accretion due to increased wind speeds or exacerbate erosion due to increased total water levels. The precise nature of these future impacts on coupled dune-beach systems is highly dependent on the degree of climate change and the pre-existing beach morphology. Climate change is therefore unlikely to impact coastal foredunes uniformly, posing a challenge for communities relying on these features for protective services into the future in the context of both increasing sea level and changing storm properties.

The DUring Nearshore Event eXperiment (DUNEX) was carried out on Pea Island, North Carolina, USA between September-October 2021. We use a coupled numerical model (Windsurf) to hindcast the evolution of the DUNEX transect and produce a time series of hourly water levels at the shoreline from the model output. In addition to assessing the ability of Windsurf to reproduce TWL, we use model output paired with an ensemble of empirical models to assess how TWL forecasts can be improved by incorporating dynamic morphology. The morphological hindcast achieved an RMSE of 0.10 m and a BSS of 0.47, while the total water level (TWL) time series from the model correlates with the U.S. Geological Survey forecast (r² = 0.61) for the study period but with a 0.47 m bias that is primarily due to the much steeper beach slope used to produce the forecast compared to that surveyed at the start of the study period. We find that using dynamic morphology provides a small but statistically significant (α = 0.05) improvement in predicting TWL versus applying the pre-storm beach slope to the whole time series.

A laboratory study was conducted to validate the accuracy of using a laser-scanner for measurements of wave run-up. A capacitance wave gauge was used in conjunction with a Riegl LMS-Z390i laser scanner, to measure wave run-up on a hardened sloped structure. The largest bias experienced between the two measurement methods was -3.9 mm, within the expected accuracy of the laser scanner. This measurement technique was applied to a physical model to evaluate the impact of belowground biomass on reducing wave run-up and demonstrated a reduction in wave run-up in lower water conditions, but deeper, more dynamic conditions result in increased variability in the data collected using LiDAR. This study demonstrated that though LiDAR is a successful means of obtaining coastal observations, measuring wave-run during extreme events can still present challenges, and means to provide repeatability both data collection and associated analysis may still be needed.

A relationship between properties of coarse lag deposits found on some beaches and variability in alongshore dune growth via heterogeneity in sediment grain size was investigated. A multi-fraction sediment transport model, AeoLis, was used to calculate volume fluxes to the dunes for a variety of spatially variable grain size distribution scenarios and wind speeds. A poorly sorted coarse deposit decreases the alongshore variability in dune growth potential when compared to a well sorted coarse deposit, particularly for smaller wind speeds. A larger median grain size in the coarse lag deposits also increases alongshore non-uniformity in sediment fluxes to the dunes. Results indicate that alongshore non-uniformity of dune growth can be partially related to spatial and/or temporal variability in the bed composition of the fronting beach.

A new artificial dune with planted marram grass was constructed in front of the traditional dike at Oosteroever, Belgium in January 2021. This artificial dune was built to mitigate the local aeolian sand nuisance on the dike. This paper focuses on the development and evaluation of the AeoLiS model for simulation of this new artificial coastal dune field. The model AeoLiS is used to hindcast nine months of morphological development of the new planted dune in front of a dike in Oosteroever, Belgium. Simulation results show that AeoLiS is capable of reproducing spatial patterns and profile development inside the artificial dune area to some extent. But the implementation of vegetation dynamics needs to be improved in the model to better account for the interaction between vegetation and aeolian sand transport. This nature-based solution offers a unique experimental setup. The complex interaction between aeolian sand transport and vegetation will ensure future morphological development of a dune body strengthening the local coastal protection.

A field experiment to study dune erosion was conducted on the Sand Engine near Kijkduin, the Netherlands, from November 7^th 2021 to January 7^th 2022. Two artificial unvegetated dunes were constructed near the high water line, and experienced significant erosion through avalanching during three storms. This paper aims to identify what drives dune erosion through avalanching by using the collected data and equilibrium theory. Results suggest that the cumulative volume eroded through avalanching during a single high water is positively correlated with the profile mismatch between the pre-storm profile and a ‘storm equilibrium profile’, described by a 2/3^rd power law, an empirical coefficient A, and the total water level. This mismatch is quantified by calculating the area integral of the profile that is acquired when the upper 35 m of the pre-storm profile is subtracted from the upper 35 m of the equilibrium profile. Avalanching commences when this mismatch becomes larger than approximately 0, after which 1 m³/m of sediment erodes from the dune face for every 3 m³/m mismatch. In addition, during one event avalanching occurred even though the elevation of the total water level did not exceed the initial elevation of the dune toe. This implies that a total water level that exceeds the initial elevation of the dune toe is not a requisite for avalanching and a collision regime to occur, which contradicts conventional definitions of dune erosion regimes. These results have implications on risk assessment of storm conditions on dune erosion.

Coastal dune development predictions require a detailed understanding of the coastal system, which includes the occurrence of marine and aeolian processes and their interactions across temporal and spatial scales. In this research, aeolian processes related to sediment properties and long-term processes related to sea level rise were investigated. Previously executed field and numerical model studies were synthesized to gain insights into the relevance of aeolian and marine processes on dune development across spatial and temporal scales. The results showed that although variability in sediment properties and sea level rise were observed in the field, their effect on dune development predictions might be limited. Quantitative predictions that are suitable for engineering will require increased effort in applying numerical aeolian sediment transport models to real-world cases with suitable monitoring data.

Traditionally, independent tools have been used to simulate wave- or wind-driven processes to simulate coastal morphology change. Coupled models that cross the land-sea division and integrate these collective processes can increase our knowledge on complex morphodynamic interactions and improve predictions of the foreshore, beach, and dune evolution. In this paper we present the initial development of a coupled modelling framework capable of numerically predicting the integrated development of coastal landforms, including both marine and aeolian processes, by using a generic model coupling approach that leverages the Basic Model Interface. The aim of this tool is to support the interdisciplinary design of Nature-based Solutions on varying spatiotemporal scales. As shown for the Marker Wadden case, the implemented model functionalities allow for the numerical description of the coast in an integrated manner and thus create opportunities for modeling coastal landform of the nearshore, beach, and dune that would not be possible with a discrete model approach. Specifically, by coupling two discrete numerical models, AeoLiS and XBeach, the aeolian and marine interaction resulted in a more realistic behavior of processes in the intertidal area. After coupling, bed levels compared better to the observations compared to the superpositioned results of both separate model components, which showed the added value and potential of coupled modelling. These findings have implications on the ability to predict spatio-temporal integrated coastal development – including these interacting aerodynamic, hydrodynamic, and ecological processes, which are essential in the interdisciplinary design of NbS.

A suite of high-resolution hydrodynamic and topographic observations during a breaching and failure event of a large (~FEMA 540) human-made southern California dune are presented. XBeach, a process-based model, is used to simulate dune erosion and breaching onset time. Brier Skill Scores (BSS) are estimated along the dune face. Use of default model parameters suggested for dune erosion demonstrates overall poor predicative skill, while utilization of 2D XBeach improves model performanc. Critically, these findings provide more field data, particularly storm-by-storm observations, which is required for better model validation, especially with rising sea levels that will dramatically increase swash-dune collision, breaching, overwash and backshore flooding in dune protected areas.

The nearshore morphodynamic model CSHORE is coupled with the process-based aeolian sediment transport model AeoLiS to explore the evolution of the beach-dune system and interactions of subaerial and subaqueous processes at Caminada Headlands (CH), Louisiana, USA over a two-year period. Vegetation is shown to play an important role in the dune growth and recovery mechanisms. The relatively low wave energy and wind intensity over the two-year period result in offshore sediment transport from dune toe and dune face, moderate dune recession and formations of sand humps in presence of vegetation according to the coupled model. The numerical tool developed in this study is capable of simulating beach-dune changes on large temporal scales (multi-annual to decadal), which is typically associated with the recovery process. This study provides insights into the extent and timescales of dune recovery at the CH. The advantages of CSHORE in computational efficiency, robustness and accuracy enable it as a good prediction tool for long-term (years to decades) evolution of beach profile. This initial application of CSHORE-AeoLiS through BMI coupling shows promise in this new coupling framework using state-of-the-art tools.

This study utilizes UAV technology including a multispectral sensor to monitor changes in marsh edge morphology and vegetation in a Louisiana coastal wetland and additionally observe the effects of storm surge from Hurricane Zeta on marsh edge morphology. This study revealed that Zeta eradicated at least 101.8 m² of vegetated marsh along the eastern edge of the study site in Terrebonne Bay. The UAV imagery demonstrated that the vegetated marsh edge hardly recovered three months after the storm. From the multispectral UAV imagery collected, an average rate of change in vegetative health between the months of November 2020 and February 2021 was calculated. This demonstrates the potential of using multispectral UAV technology to establish an approximate baseline for seasonal vegetation change. Such a baseline can be improved with more UAV surveys and employed in future studies to investigate hurricane impacts on coastal wetland vegetation with consideration of seasonality.

Elevation is a key indicator of a wetland ability to resist physical forcings such as storms and sea level rise. To better understand the interplaying relationship between elevation, belowground biomass productivity, and shear strength, two sites were investigated: a salt marsh in Louisiana facing shoreline erosion and a brackish marsh in the Everglades National Park facing saltwater intrusion. Positive correlations were identified between elevation and shear strength at both sites. However a trend was only identified for belowground biomass and shear strength at the Louisiana site which highlights the difficulty associated with sampling in a densely vegetated site. These results have implications on understanding of the impact of the vegetation-soil matrix on the strength and resilience of coastal wetlands.

This article proposes a simulation model inspirited by Mott MacDonald’s machine learning approach to develop a surrogate numerical model using historical data to learn and study the characteristics of Cameron-Creole Watershed (CCW). This surrogate model could simulate the hydraulics of the CCW thousands of times faster than the original numerical model. Mott MacDonald developed a surrogate data-driven models (DDMs) using only MIKE-Flood simulated data (from both Existing Conditions and from four with-project alternatives). The DDM could accurately predict water level for Existing Conditions and all with-project alternatives within +/-3.8 cm of the measured water levels. The DDM was then used to simulate non-uniform Flap Add alternatives, where some structure locations are given added flap gates while others are not. This was done to spatially optimize the addition of flap gates to the system. Over 8,000 configurations of non-uniform Flap Add alternatives were simulated and it was found that prioritizing addition of flap gates at Grand Boat Bay and No-Name yielded better performance than uniform flap gate additions across all structures. This conclusion would likely be unattainable using traditional numerical modeling techniques, as the simulation of this many unique configurations would be unfeasible. This study demonstrates that using surrogate modeling can be effective for simulating project alternatives within a well bounded framework if enough “with-project” model results were used to train the surrogate model.

Channel meandering is ubiquitous in coastal marshes, yet it is routinely omitted in marsh evolution models. Here we propose a simple method based on flow curvature to simulate channel meandering in coastal marshes. A first-order flow is computed based on a balance between pressure gradient and bed friction. This flow is then empirically modified to represent the shift of momentum toward the channel outer bank. The model reproduces realistic channel sinuosity and channel migration rates, and it could be used to efficiently predict marsh landscape evolution from decades to millennia.

Wetlands are examples of nature-based sustainable and resilient coastal protection solutions. However, there is a need to quantify the capacity of the marsh platform to withstand hurricane disturbance through a better understanding of the root structure architecture and strength (RSAS). Therefore, the purpose of this study is to investigate the marsh platform stability as a function of wetland root structure. This study is synergistic towards the X-ray computed tomography (XCT) Nikon XTH 320/225 system at the Environmental Molecular Sciences Laboratory (EMSL) for nondestructive studying of root-system architecture in coastal wetland vegetation. The testbeds for this study are the Atchafalaya (natural active delta) and Terrebonne (continued river abandonment) Basins to forecast how long-term vulnerability to hurricanes, coastline erosion, and sea level rise (SLR) will impact these distinct basins.

The Hammond Assimilation Wetland (HAW) has been receiving treated municipal effluent from the Hammond wastewater treatment plant since November 2006. This study examines the long-term impacts to assess the desirability and sustainability of discharging secondarily treated sewage to coastal wetlands, especially freshwater marshes. Although improvements in water quality and revitalized wetlands were initially observed, rapid wetlands deterioration was observed in HAW after a year. Several causes for this deterioration have been discussed among the coastal restoration community including herbivory by nutria and decreased soil strength as a result of high nutrient concentrations. Cone penetration tests (CPT) were performed in the summer of 2021 to assess the influence of high nutrient concentrations on wetland loss. The test results in this study provide a framework and serve as the basis for further study to understand the long-term spatial impacts of varying nutrient concentrations on soil shear strength and wetland loss.

This paper presents a one-dimensional cross-shore model to simulate sediment transport and surface elevation changes of submerged sand berms placed adjacent to vegetation. The model includes multiple processes such as wave action, wave attenuation due to vegetation, sediment transport, and morphological changes. The phased-averaged sediment transport is simulated by including driving forcings of wave, current, and gravity. The effect of wave nonlinearity such as asymmetry and skewness on sediment transport is simulated by using a nonlinear wave shape model for calculating free-stream near-bed horizontal orbital velocity. This 1-D model was successfully validated by reproducing the bed elevation evolution of the experimental berms conducted in a wave flume with rigid vegetation. The predicted sediment transport rates quantified the sand movement of the berms into the canopy.

Given its location, the Gulf Coast of Plaquemines Parish faces constant environmental threats and hazards. The parish is particularly vulnerable to tropical storm events, sea level increases, and rising temperatures. In addition, the early twentieth-century flood protection levees that were built along the Mississippi River have removed the natural sediment flows that are needed to replenish the wetlands and help reduce the subsidence of the Mississippi River Delta. This research builds on work in environmental planning and geography that examines the coastal environment as a means through which regional and racial formations are forged, particularly for African American communities in the U.S. coastal south. This work engages with emerging literature about how coastal science often reproduces racial inequalities in climate changed environments. It is in the context of this social geohistory that this paper considers the planned Mid-Barataria Sediment Diversion (slated to begin in early 2023) in Plaquemines parish to explore the relationship between coastal planning and marginality- past and present. At $8 billion, one of the most expensive, ambitious, and controversial proposals in Louisiana’s 50-year, $50 billion attempts to save the southern third of the state from disappearing into the Gulf of Mexico. However, the project is controversial among fishers who rely on shrimp, oysters, and finfish that are now harvested in the existing mix of fresh to saltwater. They contend that freshening the basin with river water will destroy their livelihoods and dilute the region’s rich culture and are mobilizing for resistance.

In the end, it is the same vulnerable and marginalized communities that have so long suffered because of racial and environmental injustice that stand to lose the most if the social costs of coastal planning in Louisiana are not sufficiently considered- as has historically been the case. In planning for land and population loss in Plaquemines, it is critical not to repeat past mistakes.

Citizen science initiatives can be a cost-effective way to obtain simple data, particularly where financial or technical capacity constraints prevent regular and systematic monitoring. CoastSnap is a citizen science approach that facilitates the analysis of shoreline changes using photographs shared by the public. To inform future projects, this paper describes project achievements and the difficulties faced by CoastSnap Mozambique pre, during and post-Covid pandemic. The CoastSnap Mozambique project installed the first CoastSnap stations on the African continent, as a first attempt to gather beach change data at sites where little or no previous knowledge was available. Poor community engagement, limited local technical capacity, and the difficulties imposed by the Covid-19 pandemic prevented the project to realize its potential. Despite many challenges, new knowledge was gained about local beach morphology, identifying specific issues and sites warranting future investigation. Lessons learned from the CoastSnap Mozambique experience can help future projects to identify the pitfalls that may be encountered in locations facing similar socioeconomic and technical limitations.

Coastal areas are the most vulnerable areas to sea level rise and coastal erosion caused by climate change. Still there is a large interest to live close to water and close to the sea. Society needs to adjust and adapt to rising sea levels, and there is a need for flexible climate adaptation strategies. It is important to include citizens and stakeholders in the planning process and for that reason it is important to have good visualization tool to be able to make good decisions. This article adopted the Swedish Geotechnical Institute (SGI) stepwise approach for flexible climate adaptation to address rising sea-levels and uncertainties in municipal planning.

The Swedish Geotechnical Institute (SGI) SGI has developed a coastal vulnerability index (CVI) for coastal erosion in Southern Sweden. This is a GIS based tool for visualizing vulnerable areas in relation to coastal erosion. The index is function of coastal characteristics, coastal forces, and socio-economic values. The index can be used by municipalities and consultants to identify vulnerable areas that need further attention or more detailed studies or climate change adaptation strategies. The CVI could be further divide into sub-indices, coastal pre-conditions and socio-economic values. We recognize several of the barriers implicit in such an approach. Legal frameworks and financial structures are normally the foundation for long term stability, but they are not always flexible over time. SGI is currently working on further developing the approach and testing it on pilot municipalities in Southern Sweden.

Most estuaries are affected by anthropogenic alternation of the quantity, quality and timing of freshwater inflows. In some cases, changes to freshwater flow regimes have been catastrophic. However, full ecological recovery of estuarine systems is rare, including because of uncertainty in the relationships between estuarine hydrological state (salinity structure, residence/flushing time, water level, and flow energy) and pressures. We focus on how freshwater restoration via the upstream manipulation of freshwater inflows affects estuary hydrological state. We apply a Pressure—State—Response (PSR) framework, where estuary state is determined by a number of interacting sub-systems including hydrological state, morphological state, and biogeochemical state. Case studies demonstrate how success of estuary restoration efforts remains difficult to define and metrics for estuaries focus largely on ecological expectations rather than the physio-chemical setting.

CoastSnap is a citizen-science monitoring project that raises public awareness to local shoreline change (Harley et al., 2019). CoastSnap was implemented in three different beach settings on Delaware’s coast in 2020. Besides successfully establishing the project, the goal of this study was to make CoastSnap a sustainable program for long-term coastal monitoring through automated workflows that eliminate repetitive manual tasks. Initially, images were processed following the workflow of Harley et al. (2019) and Harley and Kinsela (2022), which uses their open-source MATLAB code to detect the shoreline in each image. However, significant time was required to process each image due to many manual and repetitive steps. To save time, we automated parts of their workflow. This research aims to increase the number of people able to use every part of the CoastSnap process with limited coding knowledge, so that any local group or authority can easily implement a station and monitor their own shorelines for better coastal management and policy making.

This study assesses the effectiveness of SandSnap, a research initiative that engages citizen scientists in amassing the first public nationwide database of beach sand grain sizes on U.S. coastlines. Citizen scientists can contribute to the database by taking a picture of sand at a beach with a U.S. coin, uploading the image to the SandSnap website, and recording the location using the phone’s built-in GPS. Sediment gradation is returned to the user within 2 minutes of image upload and the results are stored on a public database. Image processing and outreach initiatives are detailed. Results from an experiment where 31 participants with varying phones took a SandSnap of the same sand show the median grain size had a mean percent error of 21.3%. Image processing techniques are continuing to be improved and the supporting neural networks are regularly retrained with more data to improve the accuracy and robustness of the SandSnap results. The spatially and temporally robust beach grain size database being developed by SandSnap will help to improve numerous coastal engineering analyses including coastal resilience and vulnerability quantification, beach nourishment life cycle and uncertainty analysis, beach compatibility for beneficial uses of dredged sediment, and large-scale coastal morphology modeling. Crowdsourcing beach sand grain size data collection provides a cost-effective way to accumulate unique sand grain sizes on a large scale while increasing public engagement and providing a better understanding of sand on U.S. coasts.

Participatory science programs are becoming effective mechanisms to provide members of the public opportunities to be involved in scientific research worldwide. As part of the outreach and education initiative at the Stone Living Lab, community members were trained to use the Emery method of beach profiling and conducted surveys at twelve different sites around Boston Harbor. This paper evaluates the success of this model of a one-year limited participatory science program, and evaluates the usefulness of the profile data gathered during this project from a scientific perspective. The first year of participatory science at the Stone Living Lab generated 172 beach profiles at 12 different beaches around Boston Harbor. This is a unique dataset to the area, and while it is still a relatively short record, it can be expanded upon in the future to create a picture of long-term trends and changes at these beaches. Initial evaluations of the data collected using the Emery method of beach profiling have shown that even though there is some error with the method, the elevation profiles can be useful to depict geomorphology, emerging seasonal trends, and storm analysis. The results of this yearlong project reveal that overall participants successfully used the Emery method to measure beach profiles at multiple sites. These time series data are useful to help scientists and the public document the evolution of beach state and better understand the impacts of wave energy, seasonal trends, and individual storm events.

Decades of erosion adjacent to the south Columbia River jetty, Clatsop Spit, Oregon, was mitigated in October 2013 through the construction of a cobble berm or dynamic revetment, immediately south of the jetty root. Such structures are a ‘design with nature’ approach in that the cobble berm is expected to mimic morphological responses observed on natural gravel beaches found around the world. Here we describe the primary findings from a near decade long monitoring effort that was established to document the overall performance of the cobble berm and natural sandy foredune that flanks the structure to its south. Monitoring consisted of periodic RTK-DGPS surveys of transects as well as topographic mapping. Since its construction, the dynamic revetment has been subject to major storms resulting in periodic overtopping, southward transport of gravel, and ongoing erosion of the natural foredune to the south that is independent of the structure. Besides performing as originally designed, the dynamic revetment also enjoys other unanticipated effects that further augment erosion protection. Finally, monitoring over the life of this structure demonstrates the efficacy of dynamic revetments as a viable solution for mitigating erosion on the high energy Pacific coast.

This study evaluates the effectiveness of alternative concepts for reducing erosion of Harrison County’s shoreline and extending the life of beach nourishment projects within the hotspots. A shoreline change analysis was completed to assess the entire shoreline and identify hotspots. Hotspot erosion is primarily attributable to two distinct mechanisms: coastal straightening from wave refraction, and sediment deficit from littoral disruption by updrift structures. Conceptual hotspot mitigation structures, including groins and offshore breakwaters were analyzed using a numerical model. Alternatives including groins and offshore breakwaters were effective in reducing localized erosion at hotspots, although some of the concepts caused downdrift impacts. Overall, the groins did relatively little to improve the conditions along the shoreline. Both offshore breakwater concepts performed well to reduce erosion at the shoreline. The short offshore breakwaters performed better than the long offshore breakwaters to reduce erosion at Hotspots A and C with minimal downdrift impacts along the entire shoreline. The long offshore breakwaters did perform well to reduce erosion at the hotspots and had a higher overall volume increase within the project area than all of the other concepts, but had significant downdrift impacts west of Hotspot C. Downdrift impacts are expected with any engineered solution in a littoral system. The schematic representation of these alternatives in a hydrodynamic model represents a feasibility-level evaluation of their potential performance and effectiveness. Coastal structures and configurations of such must necessarily be fine-tuned to individual hotspot locations and localized wave climates to improve performance.

The Fire Island Inlet on the south shore of Long Island, New York, has experienced significant, uneven channel shoaling and scouring since a Federal Jetty was completed in 1941. At the same time, persistent erosion has occurred in the updrift and down-drift beaches, often requires periodic nourishment to stabilize the local shoreline. Supported by the US Army Corps of Engineers (USACE) District, New York, a numerical modeling study with the field data collection effort is presently conducted to explore engineering solutions to improve the inlet channel maintenance and identify potential ebb shoal borrow areas for the nourishment in the updrift and down-drift beaches. New field surveys have indicated a drastic decrease of sand outside inlet and along the adjacent coast. The numerical modeling includes two alternatives, Alt 1 and Alt 2, both having the same sediment deposition basins located along the east side of the inlet channel and an ebb shoal borrow area west of the entrance channel but with different volume of sand removed from the borrow area. A Coastal Modeling System (CMS) developed at ERDC was applied in the present study for one-year simulation of April 2019 to March 2020. The modeling result shows the inlet sediment management can benefit from a partial ebb shoal borrow area design to assist the updrift and down-drift onshore nourishment applications. Both alternatives appear to be equally effective, hence the final selection may depend on the O&M budget and further consideration of potential occurrence of severe storm events.

Sandy spits are quite frequent phenomena at river mouths but remain relatively rare for the largest rivers considering that their hydrodynamics generally prevent the creation of such sedimentary structures. In 2003 a trench was dug on this spit to relieve City of Saint-Louis from flooding, the river immediately used this depression as a new access to the Ocean, causing the disappearance of the major part of the sand-spit named the Langue de Barbarie. Since then the spit is rebuilding progressively and hence is a formidable laboratory for studying sedimentary dynamics. This study, carried out as part of the MEPELS project (Modeling and Evolution of Sandy Beaches and Coasts), makes it possible to review the methods for implementing the models and their validation because the geographical and temporal scales of the variations and the multiple processes involved in play seem too complex to be all included in a single model. The surface calculation method applied here will thus be able to know in the near future volume of sediment, thus allowing to obtain the variability of sedimentary fluxes at the scale of a satellite image, a region, a country or a continent. Shoreline data show that the recurrence of measurements has a strong impact on the perception of coastal dynamics. This relativizes the results based on comparisons of data acquired over short periods and poses a real problem of the conclusions about results of modeling that is often carried out on exceptional short-term processes.

“Fools Cut” opened in 2017 through the remnants of South Beach in Chatham, MA and created a new hydraulic connection between the Atlantic Ocean and Nantucket Sound. Strong, nearly unidirectional, tidal currents have impacted sediment transport patterns, leading to more rapid erosion of Morris Island and the USACE dike/barrier beach that extends to the entrance of Stage Harbor. In addition, material eroded from the beaches and nearshore area is rapidly shoaling the Stage Harbor entrance which is a federal navigation project (FNP), leading to significant navigation safety and sustainability concerns. Given that westerly dominated, nearly unidirectional tidal currents through Fools Cut. This article proposes to develop a method to control river bank erosion and/or redirect river currents (e.g., IDNR, 2006) to deal with the impacts of Fools Cut on the Stage Harbor FNP and Crescent Beach. Although shoreline change was not directly modeled with the Delft 3D analysis, the final selected array alternative illustrated substantial reductions in tidal current velocities along the Crescent Beach shoreline. In addition, this reduction in current velocities occurs both downstream (west) and upstream (east) of the proposed structure arrays. As the influence of tidal currents is directly responsible for rapid erosion of Crescent Beach, these reductions in nearshore tidal velocities will substantially improve long-term beach stability. This final alternative developed in this study offers the best overall performance and also is sited to minimize impacts to the Monomoy NWF and USACE project. This alternative reduces sediment flux toward the Stage Harbor FNP by 60 percent, while greatly curtailing erosional currents along the narrowest area of Crescent Beach, and has no structural elements within the Monomoy NWR.

Wave overtopping and beach lowering are dynamically linked processes, and vital to the management and design of sea defence infrastructure. However, these interactions are poorly understood and therefore not well represented in existing overtopping tools, such as EurOtop, used by coastal managers. There is a paucity of high resolution (field) data on beach dynamics in front of coastal structures. Here we demonstrate how a low cost, reliable, standalone bed-level sensor (B-Scan) capable of capturing daily beach profile response can support operational management decisions. Results from four sites demonstrate a robust system that can be used to improve the accuracy of operational overtopping forecasts and asset management. The system has exhibited resilience, reliability and accuracy earning support from additional stakeholders keen to improve the monitoring at further locations. With a reliable range of 12-15 m the B-Scan sensor can provide a good representation of beach response to forcing conditions, in front of sea walls, that can be used for asset management and coastal flood forecast. The system can be used in a wide range of settings mitigating the need for site visits to understand beach state to aid in coastal management. The improved temporal resolution of the data can demonstrably improve the accuracy of overtopping forecasts important for coastal flood management and help to generate greater confidence in coastal flood forecast systems.

The paper presents three dimensional simulations of scour around a rectangular pile with different aspect ratios under combined wave-current flow conditions using a computational fluid dynamics model, REEF3D. The Reynolds-averaged Navier-Stokes (RANS) equation is solved using the k-ω turbulence model in the present work. The Exner equation is used to measure the variations in bed elevation. The level-Set approach is used to capture the free surface realistically. The numerical model couples the hydrodynamic module with the morphological module to simulate the scour process. For accurate erosion and deposition calculations in the sediment bed, the morphological model employs a modified bed shear stress formula on a sloping bed in combination with a sand slide algorithm. In the present study, the simulations have been done in a truncated numerical wave tank with the Dirichlet boundary condition and active wave absorption method. The validated numerical model is utilized to study the effect of the aspect ratios and the effect of KC number in the combined wave-current environment. Maximum scour can be seen for the aspect ratio 2:1. It is also observed that the normalized scour depth increases as the KC number increases for a fixed Ucw.

APTIM was contracted to assist Long Beach Island Township (Township) in developing recommendations for the possible modification of the groin field within the southern end of their beach nourishment program (Holgate Avenue to the terminal groin). Since the construction of the federal shore protection project by the USACE, the beaches at the south end of the Township have experienced high erosion losses despite the historic groins being in place. The study objective is to evaluate through numerical modeling various alternative groin designs to optimize the preservation of the Township beach nourishment sand volumes, while bypassing sand appropriate volumes of sand to the E.B. Forsythe National Wildlife Refuge-Holgate Unit to the south. After 7 years of model simulation, the placement of an extended notched terminal groin (Alternative 10) shows similar results to the extended terminal groin without the notch (Alternative 9). Compared to the Existing Conditions, the longshore transport is increased by 8% for Alternative 9 and 9% for Alternative 10 at the Holgate terminal groin. Both alternatives reduce the magnitude of the longshore sediment transport at 1000 ft and 3000 ft south of the Holgate Terminal groin compared to the Existing Conditions, ranging from an 18 to 30% decrease. All three, final combined alternatives simulated show improvement in beach stabilization at the southern end of the Township beach.

Coastal barrier systems are important features that protect the landward environment from the impacts of storms and are economically and ecologically valuable. This study investigates the impact of storms on two unique coastal barrier systems in southern Rhode Island. The two study sites, the Charlestown Town Beach system, and Moonstone Beach within the Trustom Pond National Wildlife Refuge, vary in their anthropogenic influence, which is believed to have significantly affected their evolution. Through the analysis of historical and terrestrial LiDAR, the changes in morphology and character of these two study sites due to historical and recent storm events are investigated. Hurricane Sandy caused extensive dune erosion throughout these two coastal barrier systems, but CTB has recovered in height and volume while TP remains locally low and vulnerable for continued overwash. These differing responses require differing approaches to their management. A more recent, but weaker storm event in November 2022 showed impacts that were limited to the lower beach, suggesting recovery since Sandy has limited recent overwash, but some slight dune erosion and steepening of the foreshore which was captured with terrestrial LiDAR. Terrestrial LiDAR is a useful tool for investigating forecasted events, since it can be deployed directly before and after a storm, allowing for the acquisition of frequent high-resolution data. This study is part of a larger NOAA-funded effort that aims to support mitigation decisions related to storms and sea-level-rise in coastal New England.

Coastal sediments are important sites for carbon and nutrient cycling, marine infrastructure, and habitats for infauna. Extreme storms can dramatically alter sediment distributions and kill infauna through sediment erosion and redeposition. However, little is known about how infaunal communities are affected by and recover following storms. We investigated changes to sediment grain size and infauna at 5 m, 12 m, and 20 m depths on the Alabama coast following Hurricane Sally (2020). We hypothesized that Sally would alter sediment structure at all sites and that erosion and transport from the shoreface would produce distinct storm beds. Here we present preliminary data from one shallow and one deep site, showing altered sediment structure and decreased infaunal abundance following the storm and recovery by the spring. These results will provide insight on how hurricanes impact sediment and infauna as well as the short- and long-term impacts of community recovery on sediment stability and transport.

The purpose of this study is to assess how the deposition and mobilization of Hurricane Harvey (2017) flood deposit and elevated subsidence has impacted sedimentation within Galveston Bay. The Bayport Flare/Channel, located with the San Jacinto Bay (SJB) portion of the northwestern corner of Galveston Bay, has experienced a 25% (6.25% annually) increase in siltation since Hurricane Harvey (2017). The floods associated with Harvey deposited 131.34×10⁶ tons of sediment in Galveston and in the four years after Harvey, 27% of the deposit has eroded, increasing the bay’s suspended sediment load by 9% annually. SJB has subsidence rates of 1.5-2.2 cm y^-1 and has an average sedimentation rate of 2.6 cm y^-1, indicating that SJB is a net sediment sink. Sediment Trend Analysis (STA) was performed on a grid of sediment grab samples from the SJB area and reveals sediment transport convergence from all sides of SJB, with the dominant pathways from the most exposed portions of Galveston Bay to the south and southeast. This study concludes that the elevated siltation within the Bayport Flare/Channel is likely sourced from the eroded sediments sourced from the Hurricane Harvey flood deposit within Galveston.

Animals that live in marine sediments are known to drastically modify the physical characteristics of their habitats. Infauna can increase sediment strength by increasing cohesion through mucus secretion and compacting sediment during tube building. Alternatively, infauna can weaken sediment by disrupting cohesive bonds and excavating burrows. Linking infaunal behavior to sediment physical properties can improve understanding of object-seabed interactions, e.g., unexploded ordinance detection and management. This study aims to characterize impacts of infauna on sediment strength by sampling different sediment communities inhabiting sediments with similar grain sizes. Data processing is ongoing, but preliminary observations of infauna from three sites sampled along the York River Estuary show different dominant taxa among sites. Burrowing bivalves that possibly weaken sediment are abundant in the upper estuary, and tube dwelling organisms that possibly strengthen sediment are abundant in the lower estuary. The results of this study will improve interpretation of PFFP data in areas with abundant infauna, as well as improve our knowledge of how infauna interact with their environments and affect engineering properties of seabed sediments.

Marine benthic photosynthetic communities are a ubiquitous presence in the nearshore environment which constitute a vast amount of organic material known to produce cohesive extracellular polymeric substances (EPS) for a range of behaviors. Laboratory-derived, theoretical nearshore sediment dynamics omit the biocohesive effects on nearbed suspended sediments and bedform morphology. Therefore, we present in situ findings from a nearshore moored platform experiment aimed at identifying the cohesive effects of EPS on sediment dynamics and bedform morphology. Time series cross correlations indicated significant, direct correlations of diatom biomass to water column chlorophyll a concentration, sediment Hazen Uniformity Coefficient, and ripple defect density. Biomass was indirectly correlated to total sediment concentration and velocity. Comparison of the diatom biomass to bedform roughness and the variability of defect densities in relation to hydrodynamic forcing highlighted the ability of well-developed diatom populations to decrease ripple mobility in changing conditions and the lingering temporal effects of spatially heterogeneous diatom biomass on ripple morphology variability. Preliminary results presented in this work show the capability of benthic diatom biomasses to exert a cohesive effect in a noncohesive environment, providing additional insight on the evolution of bedforms and its impact on sediment flux in the shallow continental shelf.

In this study, the field measurements with LISST-100X, water sampling and so on, were carried out in the Port of Niigata to quantify the in-situ particle properties of river-derived suspended sediments. The majority of the river-derived sediments by volume were transported into the port as freshwater flocs. The freshwater flocs are likely further aggregated due to contact with seawater in the dredged area. The settling velocities of the freshwater flocs and the further aggregated seawater flocs can be up to about 15 and 80 times larger than those based on the primary particles, respectively. These findings suggest that both the transport of freshwater flocs and their further aggregation due to contact with seawater are important processes for deposition of fine sediments in the port.

The Department of Natural Resources (DNR) aims to reduce the sources of toxic chemicals in Puget Sound by removing derelict creosote-treated pilings and overwater structures from coastal areas. DNR considered to remove a densely-packed timber pile field at the site of former Dickman Lumber Mill, Tacoma, Washington. However, the pile field removal poses a risk due to additional sediment mobilization and release of contaminants of concern (COCs). A numerical study was conducted to support DNR evaluate potential movement of COC-laden sediments in the nearby coastal areas following pile field removal. Fully-coupled hydrodynamic, wave and sediment transport modeling was performed for storm conditions. Modeling results included hydrodynamics, waves, suspended sediment concentrations, and resulting bed changes. Results indicate that COC movements outside the project area are only likely to occur for cohesive sediment fractions, which are mobilized outside the pile field and are likely to deposit as a thin veneer on the seabed.

Alviso Slough in South San Francisco Bay has been experiencing restoration of adjacent former salt-production ponds into muted tidal ponds, tidal ponds, and salt marsh. As a result, tidal prism through Alviso Slough has increased and mercury-contaminated sediment has been remobilized. We developed a 2D, high-resolution, process-based model (Delft3D FM-wave) to hindcast observed morpho-dynamic developments and to investigate associated sediment flux in the slough and pond system. Our results contrastingly demonstrate that a successful hindcast of the observed morphodynamic trend is made while reproducing observed intratidal suspended sediment concentrations in Alviso Slough remains a challenge. Our explanation is that the model is able to capture spatial gradients in the tide-residual sediment transports as the result of the large-scale management actions in the system, i.e., the opening of the salt ponds. These tide-residual processes are generally difficult to measure over an entire domain, but are very relevant to model the morphodynamic development. Our model provides a promising tool to trace eroding contaminated sediments to the benefit of restoration project managers and to support planning and design phases of adaptive management measures.

Beach morphodynamics are associated to complex sediment transport mechanisms, where the textural signature of unconsolidated materials can change, either by a natural selection of some grains to the detriment of others, or by fragmentation or aggregation of the sediments in transit. In this paper, a high-resolution analysis of the grain-size distribution of a bed composed with different non-cohesive sand mixtures and subjected to the same hydraulic conditions is assessed using a coulter counter. The input of sediments with different properties than the native sediments (e.g., in beach nourishments operations) can also play an important role in morphological changes. Therefore, the analysis of sediment characteristics is required for morphodynamic modelling and for many geo-engineering studies. The possibility to use a coulter for counting and sizing particles of heterometric sediments presents obvious advantages, when compared to the classical sieving technique. Our results highlight the existence of vertical stratification and segregation in granular materials.

Wave flume experiments investigating the cross-shore transport and accumulation patterns of non-buoyant microplastic particles under irregular waves propagating, shoaling and breaking on a live sediment bed are considered. Eighteen microplastic particle groups having variable shape, density and size are tested. The experiments considered a pre-developed singly-barred profile, reasonably representative of field conditions. Four different microplastic accumulation hotspots are identified: (1) the offshore toe of the breaker bar, (2) at the breaker bar, (3) the plateau region between the breaker bar and beach, and (4) the beach. The accumulation patterns primarily fall within three different particle Dean number regimes (ratio of the characteristic wave height to the product of the settling velocity and characteristic wave period). For the parameter space tested, the dominant transport direction generally depends on the importance of offshore-driving gravitational effects and onshore-driving effects associated with nonlinear wave shapes. Particle position relative to the jet of plunging breaking waves likewise plays a key role in determining the net transport direction, especially near the breaker bar. These results help to improve understanding of the transport mechanisms and accumulation patterns of microplastic particles in e.g. nearshore coastal environments is required, as a prerequisite to any successful management or mitigation strategies.

The present study aims to add a novel data set on the incipient motion of a broader array of microplastic particles, on a live sediment bed comprised of finer sediment grains than those used by WS19. The incipient motion of 65 microplastic particle groups, having both regular (57) and irregular (eight) shapes, are investigated experimentally in a circular flume. Regular shapes considered include spheres, circular cylinders, circular disks, square plates, cubes, square prisms, rectangular prisms, tetrahedrons, and fibers. The present data set is combined with another from the literature, and the incipient motion conditions of the collective particles are systematically analyzed. After accounting for (1) differences in static friction as well as (2) hiding-exposure effects, reasonable agreement with the classical Shields curve for the incipient motion of sediments is achieved. These results provide deeper understanding of the fundamental transport properties and patterns of microplastic particles, on which is based the development of any successful management strategies.

Previous laboratory tests, conducted mainly in large wave tunnels, have shown that the transport of heterometric sediments in wave dominated flows is subject to hiding and exposure effects, which can deviate the transport rates obtained from well sorted sediments. The present work presents the results of a sand tracer experiment performed in the Large Wave Flume (GWK) in Hannover. The present results have shown that the sediment transport rate of a certain fraction in a sand mixture is not equal to the transport rates of the same fraction in case of uniform sand for the same hydraulic conditions. Selective transport processes occur, with the finer sediments being protected by the coarser sediments, which in turn are more exposed to the flow. These processes influence the transport rates of the different fractions, with a preferential transport of the coarse fractions of the mixture. The total and fractional sediment transport rates obtained contribute to gain insights on the dynamics and transport of sediment mixtures under full-scale free-surface waves, to extend the previously experimental results obtained in oscillatory water tunnels and contribute to a date base useful to validate multi-fraction sand transport models.

We outline methods for collecting Structure from Motion (SfM) data on two gravel beaches in Massachusetts, USA in order to move toward a rapid and rigorous method of capturing beach slope, grain size and other parameters of gravel beaches. The collection methods at both locations produced high quality datasets that contain more data, in places, orders of magnitude more, than standard GPS profiles (Figure 3). Direct quantifiable comparisons are difficult however, owing to the difference in processing regimes used. On Rainsford Island, a very dense point cloud was created in Agisoft using ‘High’ quality densification setting. At Duck Harbor Beach, a less dense cloud was made with Pix4D’s “Optimal” densification setting. Which is preferable for this method is beyond the scope of this paper, but both Agisoft and Pix4D are commonly used SfM programs capable of delivering accurate surface reconstructions, and processing settings should be tuned depending on features of interest. The utility of beach slope and grain size data continue to be invaluable datasets and using SfM and RTK-GPS data to develop 3-dimensional beach profiles can broaden the utility of the data, particularly along gravel beaches. These coarse-grained beaches have not received the same attention as sandy beaches due in part to the difficulty in collecting and analyzing sediment samples. The methods described herein are well-suited to rapidly and quantitatively collect information on beach slope and grain size using well-established SfM data collection and processing protocols.

We demonstrate the prediction of sandwave height based on a semi-empirical, which combines the analytical expression for bedform growth and migration from Wengrove et al. (2018) with an empirical model that estimates bedload sediment flux. The proposed model shows improved rmse when compared with the standard fully empirical methodology for predicting sandwave. The benefit of this type of model is that it is fairly simple, and with a local stream gauge, could be used by managers to predict changes to sandwave height over time. The proposed model requires very few inputs and is not computationally expensive. The model success is twofold, 1) it has a parameter that allows for growth/shrinking and migration, and 2) it is integrative, and uses the past to predict the present, which is important for geomorphologic evolution. These findings have implications for civil infrastructure crossing underneath major rivers that many very important industries around the world depend on.

A model for simulating the migration of tidal inlets, called ShorelineS, has been improved to include littoral sediment bypassing and an ebb-tidal delta in order to more accurately predict the rates and patterns of inlet migration. The model was tested on the migrating Ancão inlet in Portugal from 1998 to 2015, and the resulting shoreline evolution agreed with observations. Widely accessible satellite images and shorelines extraction tools allow for the estimation of the bypassing fractions. By including the effects of littoral sediment bypassing and the ebb-tidal delta, the model was able to more accurately predict the evolution of the coastline and the migration of the inlet amidst natural and anthropogenic factors.

As a first step toward the buildout of a United States west coast coastal storm modeling system (WC-CSTORM), we present a model test bed that can support various wave and circulation model configurations and contains a host of available observational datasets for calibration and evaluation. This test bed, located near the city of Newport, OR, contains two tidal inlets (one engineered and one with a natural mouth), a headland, and both complex and simple shoreline geometries. A simple hindcast configuration of two-way coupled SWAN and ADCIRC with forcing derived from local observations delivers promising performance during a recent wave-focused field effort with nearshore significant wave heights exceeding 5.5 m. While model performance is promising, it remains clear that waves constitute the dominant component of total water level outside the estuaries, and that accurate representation of the largest wave heights should be an ongoing focus of the modeling effort. This test bed serves as the starting point for similar regional model domains that will span the United States west coast.

This study employed advanced numerical models to evaluate the performance of various supplemental excavation areas within and adjacent to the East Pass federal navigation channel. Detailed data collection and field measurements provided the input data for model development, validation, and model boundary conditions to evaluate the feasibility and performance of these supplemental areas. The study show supplemental sediment excavation within East Pass can feasibly provide increased volumes of beach-quality material to balance erosion on adjacent eroding beaches, extend the life of proximate beach restoration projects, and extend the anticipated maintenance dredging interval to reduce potential impacts to the local economy. The proposed supplemental excavation provides a very cost-effective sand source to help mitigate erosion on the adjacent gulf-front beaches, greatly reducing costs for beach restoration. The extended maintenance dredging frequency of the federal navigation channel will also reduce local and federal maintenance dredging costs.

Understanding coastal sediment transport pathways is essential for effective management of coastal systems. To quantify the patterns underlying these pathways (Lagrangian Coherent Structures), we calculate Finite Time Lyapunov Exponents (FTLE) in the sediment transport velocity field using a sediment transport particle tracking model, SedTRAILS. We simulate an idealized sandy tidal inlet system over the course of a single tidal cycle. Here we show that FTLE patterns indicate barriers to sediment transport and zones of sediment dispersal. These patterns can be used to inform strategic placement of sediment for coastal nourishments and to develop testable hypotheses explaining sediment pathways. The spatial patterns of LCS vary in space and time with the different stages of the tidal cycle. Areas of convergence corresponding to backward LCS ridges are barriers to transport, while areas of divergence corresponding to forward LCS ridges are highly dispersive. This approach also presents new opportunities for testing hypotheses about the patterns underlying sediment transport pathways.

Tidal inlet evolution along modern sandy barrier coasts is driven in part by the complex interplay of human engineering, longshore sediment transport, variations in wave climate, sea-level rise, and the influence of framework geologic features, among other factors. As such, the overall trajectory and stability of inlets remains challenging to predict. The aim of this study is to provide new insight into the controls on the evolution of engineered inlets through detailed desktop, field, and numerical modeling analysis of Indian River Inlet, Delaware (USA). This work synthesizes and tests prior hypotheses using new tools and bathymetric and geologic datasets. Highlights include: 1) over the last 20-30 years, the channel thalweg has widened at most locations within the inlet, but most side slopes have not changed; 2) The maximum scour depth increased linearly at most cross-sections from 1941 to 1994; and 3) The inlet-average cross-sectional area (~3, 150 m²) may be approaching the minimum size necessary for equilibrium and reduced velocities, though this interpretation is not definitive. Overall, the analyzed data and prior studies indicate the combined importance of both hydrodynamic (i.e., macro-turbulence and eddies) and geologic (i.e., unconsolidated muds and stiff sands) controls on inlet-evolution over years to decades.

Thirty (30) topographic and bathymetric surveys of Sebastian Inlet, Florida, conducted between 1989 and 2007 are used to examine the behavior of the beaches immediately north of the inlet. These surveys are subjected to both conventional volumetric analyses and a two-way (i.e., planform) Empirical Orthogonal Function analysis. The 2^nd spatial eigenfunction clearly identifies the seasonally varying fillet, the upper portion of which extends nominally 690 m to the north, whereas a lower portion extends 460 m to the north where it then melds with the seasonal formation and recovery of a longshore bar. Both the volumetric changes and the temporal coefficients associated with the 2^nd function strongly correlate with the seasonal variation of S_xy, computed from a nearshore synthetic wave record that has been locally validated with in situ wave measurements. The major objective of this study is to seek correlation between the surveyed morphologic changes of the inlet’s north fillet, and the concurrent nearshore wave climate. Not only are the expected seasonal oscillations of interest, but also are any variations in the seasonal behavior. Of additional interest are any long-term trends that might be identified, including possible ongoing growth in the volume of the fillet, and the extent of the influence of the inlet to the north.

Exposed to extreme cyclonic episodes and the progressive rise of sea level in relation with climate change, the coastlines of the Caribbean are subject to natural hazards such as coastal erosion and marine inundation. The associated risks relate mainly to the safety of goods and populations, but also to the tourism economy linked to the maintenance of beaches and the natural heritage of these interface environments where biodiversity is particularly rich (mangroves, coral reefs, meadows).

The CARIB-COAST project (2018-2022, https://www.carib-coast.com/en/), was set up to develop a modelling platform for hydrodynamics, to monitor the coastal erosion and mitigation using natural ecosystems so as to assist decision-making, exchange, training and sensitization of Caribbean stakeholders to manage the risk and adaptation. The use of operational tools, the dissemination and availability of the results via a web portal and the actions of training and awarness. All the results of the project are available on the carib-coast website (www.carib-coast.com), including the modeling platform that provides with a insight on all the modelling effort of the project on present-day and future oceanic circulation and climate, tsunami and hurricanes hydrodynamics.

Embayed beaches rotate due to changes in wave climate and sediment supply. Several studies have examined embayment rotation at specific sites, but few have examined larger scale regional responses. Here, a newly available satellite-derived shoreline dataset is used to assess the geographic and morphometric controls of regional variability in embayed beach rotation along approximately 1400 km of sandy beaches along the southeast Australian coastline. Results show a high degree of coherence among beach rotation at the regional scale. In addition, the data was divided into five clusters linked to morphometric characteristics that control their differing responses to seasonal and interannual variability of the regional wave climate. Given the prominence of embayed beaches around Australia as well as globally combined with the seasonal to interannual modulation of wave climates in other regions worldwide, the methodology of this work provides a framework that can be extended to embayed beach systems elsewhere.

Denmark has an 8,750 km long coastline with a heterogeneous set of coastal cliffs in previously glaciated landscapes. The erosion of those cliffs is a complex interplay between a number of marine, coastal, terrestrial, anthropogenic and atmospheric factors. Currently, we lack a basic understanding of processes leading to cliff erosion and factors influencing coastal cliffs morphology. In this study, we delineate cliff profiles along all the shores of Denmark and combine the morphological indices of those cliff profiles with coastal environmental factors. Most cliffs are located in areas of Weichselian glacial deposits and they show different cliff morphologies than those in pre-quaternary bedrock outcrops. The highest rates of cliff top and cliff toe change are observed at the west coast of Denmark, where cliffs are consisting of sand and are exposed to high-energetic wave conditions from the North Sea. To protect coastal communities effectively, it is crucial to better understand the processes that drive coastal cliff erosion and its associated erosion rates.

A ‘Coastal Omni-Line’ approach is introduced, synthesizing multi-method coastal data to 30-m spaced transects along a single baseline shoreline, designed to address a variety of coastal research-management problems at multiple scales, from ‘primary’ (regional) to ‘tertiary’ (local) compartment scale. This approach is applied to the Australian state of Victoria, using data from the Victorian Coastal Monitoring Program, and other sources (e.g., satellite imagery, wave models, coastal morphology). Example applications include: (1) a regional assessment of shoreline trends, shoreline type and wave height; and (2) a local-scale application designed to detect erosion hotspots. Due to the flexibility and scalability of this approach, it is recommended that is be adopted in other jurisdictions, at national- to global-scale.

Minjerribah (South Stradbroke Island) Queensland, Australia holds significant natural, cultural and socio-economic value. Utilising topo-bathymetric survey and satellite derived shorelines this paper summarises the open ocean coastline evolution, post the stabilisation of the updrift entrance and implementation of a permanent artificial sand bypassing system in 1986. The southern 2 km of the island is characterised by a decadal adjustment of the coastline to the stabilisation works, artificial and natural bypassing and developing ebb-tide delta. The chainage region between 2 and 7 km (from south) is the alongshore limit of the influence of the entrance works and bypass system, taking around 10-20 years to reach its new dynamic equilibrium. North of this, the coastline appears to show no long-term response to the southern end works. The northern end of the island (chainage 19-21 km) is characterised by a spit development and is controlled by the natural longshore sediment transport rates and hydrodynamics of the northern entrance. Assessing the long-term changes to the downdrift coastline allows for a better understanding of current management practices and will provide a baseline for future coastal management interventions, such as the onset of the 2023 sand-backpassing program (City of Gold Coast, 2022).

During strong storms in the Bay of Fundy, storm surge and large waves can create hazardous conditions if they coincide with high tides. Due to climate change, the risk for future storm inundation is expected to increase, with more frequent, and higher intensity storms predicted to impact this region. To forecast these conditions, a real-time hydrodynamic model is applied to the Bay of Fundy to predict storm surge and waves over a timescale of 48 hours. High resolution spatially varied wind and pressure fields are used to drive the model, and incoming tides and waves are accounted for using inputs from larger scale ocean forecast models. Predicted water levels and waves are compared to real-time monitoring data. The model uses an open-source approach with a relatively low computational demand, making a useful method that can be applied to other coastal regions.

Coastal erosion at Pakefield on the UK east coast is currently impacting local communities and presenting several coastal management challenges. This paper presents the physical and numerical modelling evidence used to inform the current management strategy for Pakefield. It draws on broad literature, historical and contemporary observational data and modelling to reduce the uncertainties associated with predicting the short- to medium-term behaviour of Benacre Ness. This dynamic coastal feature is migrating northwards and is expected to provide natural coastal defences in the future. The interactions with nearshore sandbanks demonstrate that Pakefield cannot be considered isolated from the large-scale, long-term coastal evolution between Lowestoft and Covehithe. The future migration rate of Benacre Ness has upper and lower bounds of 25 m/year and 80 m/year, respectively. However, the current consensus view that Benacre Ness will move north and that it is only a matter of time before it arrives at Pakefield carries significant risk. Changes to offshore sandbanks and coastal orientation may reduce the migration rate and delay coastal protection along the eroded frontage. The policy decision for Pakefield based on technical, environmental and social criteria remains unresolved. In considering options to prevent further erosion or finding adaptive strategies to accommodate natural coastal evolution, recognition must be given to the inherent uncertainty in predicting the future evolution of the Pakefield frontage. Any future coastal protection and management options must adopt a precautionary approach. Specifically, any coastal protection measures must not interfere with the long-term coastal processes and ensure that Benacre Ness’s integrity is maintained.

The focus of this paper is on the development and application of a reduced-complexity shoreline model that explicitly accounts for the enhanced shoreline changes that occur due to water level changes. Contrary to previous shoreline models, this model accounts for wave and water level disequilibrium as well as passive flooding, which makes it suitable for simulating shorelines with large water level fluctuations. The model was applied to four segments of Lake Michigan shoreline. Shoreline time series were extracted from high resolution multispectral satellite images and used for calibrating and testing the model. The model was able to accurately simulate the observed shoreline changes at the four sites and reproduce the seasonal and interannual shoreline changes. The simulation results highlight the relative importance of the water level disequilibrium and waves disequilibrium for each site. Additionally, the results highlight the potential importance of accounting for other coastal processes in the proposed model.

Free-of-charge publicly available optical satellite imagery can now be used to provide short-term to multi-decadal shoreline satellite-derived shoreline (SDS) data, with errors typically under 10 m on microtidal beaches. However, SDS accuracy dramatically worsens at high-energy and/or meso to macrotidal low-gradient beaches, which challenges a robust assessment of shoreline variability and trends. In this contribution, we demonstrate that, on such beaches, water level (tide + runup) correction and/or an adapted space-averaging of uncorrected (noisy) SDS dataset can substantially reduce uncertainties and thus allow addressing the time- and space variability of shoreline change and their primary drivers. It suggests that such SDS analysis can be performed along any coastline in the world in order to guide future model development and application. Given that tide, and particularly runup, corrections at this coast dramatically decrease SDS errors, we hypothesize that such correction could allow narrowing the moving average window and thus provide higher spatial resolution information on shoreline response at high-energy and/or meso to macrotidal low-gradient beaches. These findings have implications on the forecasting of shoreline change across a wide range of time scales, including e.g. short-term storm erosion, interannual shoreline variability enforced by large-scale climate patterns of atmospheric variability, and multi-decadal change driven by various processes such as sea-level rise and coastal sediment supply.

Arctic deltas are expected to undergo dramatic shifts in their morphologic structures with the accelerated decline in sea ice. There is little understanding of how arctic deltas have developed under ice and investigating their progradation may be the best way to gain an insight into how their morphology may change in the future. Therefore, we have constructed a 2D across-shelf model using Delft3D to examine arctic delta progradation using a moving floating (barge) structure to simulate the effects of sea ice. Through model simplifications we have constructed a representative arctic delta growth under seasonal shorefast ice beginning in the mid-Holocene (6 ka). The 2D model is based on the Colville River Delta in Alaska for our case study. Model results showed sea ice changes delta morphology by altering the hydrodynamics in the nearshore system and producing a subaqueous delta. This is useful to determine arctic delta’s future morphologic structures as arctic systems continue to warm.

The knowledge of future long-term sandy shoreline evolution is necessary for sustainable coastline management. However, the impact of sediment transport due to headland sand bypassing is not yet well addressed in shoreline models. This work aims at implementing a parametric expression for sand bypassing in the reduced complexity shoreline model LX-Shore. The parametrization of the wave-forced sediment bypassing around an isolated headland developed by McCarroll et al. (2021) is implemented. Considering an idealized configuration of a 300-m long, initially straight, sandy coast with a rectangular headland, results show that headland sand bypassing has a substantial impact on the downdrift (updrift) erosion (accretion) pattern and magnitude. Our simulations imply that taking into account bypass transport in long-term shoreline models such as LX-Shore could provide new insights into coastal embayment changes.

Shoreline change is by nature a complicated process that has proven challenging to predict with current numerical models. We implemented a Deep Learning model to forecast interannual shoreline evolution driven by waves. The Deep Learning approach more accurately reproduced the interannual variability of the observed time series when compared to two previously published shoreline models. These results indicate that Deep Learning can provide improved accuracy over current models. These findings support the use of DL models as an appropriate novel tool for shoreline time series prediction, particularly to better reproduce interannual shoreline variability.

This study aims to explore the applicability of different EBSEM for the analysis of the beach profile and planform variability of Porsmilin Beach, located in a macrotidal environment in northwestern France. The models present a strong predictive capability in the upper part of the beach, where the sediment dynamics are closely dependent on the incident wave energy. However, the performance of this kind of model decreases in the lower part of the beach, where the relationship between the sedimentary dynamic and wave characteristics is more complex with the formation of e.g. growing bars. In this study, the z = 3.4 m contour has shown the best predictive capability. The YA09 and JA15 models have been able to satisfactorily reproduce the shoreline evolution due to cross-shore sediment transport at the higher contours of the beach profile at Porsmilin Beach.

Earth observation (EO) coupled with novel image analysis techniques have demonstrated the potential of EO for long-term, local, regional, and even global scale investigations of shoreline change. However, satellite-derived shoreline (SDS) data is associated with large uncertainties relating to environmental factors, tidal range, and wave action among other factors. This contribution investigates the impacts of morphological and hydrodynamic setting on the accuracy of SDS in macrotidal, highenergy coasts. Results revealed significant differences in SDS accuracy between the two morphologically contrasting sites in terms of the level of error and the optimal water level correction. We show that SDS accuracy at macrotidal sites can be greatly improved by applying appropriate water level corrections and that a different approach is required depending on beach type (dissipative/reflective). Accuracy of SDS depends on chosen proxy shoreline and varies with beach type and shoreline translation method. These results suggest the potential of SDS to help with robust and accurate long-term mapping of the shoreline, which is a fundamental requirement for effective coastal management and policy making.

This study aims to identify the natural processes and the subsequent responses to coastal engineering and development on the alongshore evolution of the IB-BI-LBI inlet-barrier system. The primary focus will be the quantification of barrier island and inlet sediment partitioning at decadal to centennial timescales, from 1839-1941. We analyze historical alongshore evolution and track coastal engineering efforts at the Island Beach–Barnegat Inlet–Long Beach Island, NJ barrier-inlet system, which has transitioned from natural to highly developed over the past 180 years. We build a quantitative mass-balance framework that tracks sediment reservoir volumes and transport fluxes within the barrier-inlet system to describe both the natural and developed alongshore evolution of this system. We find that minor coastal engineering efforts, including the construction of small-scale wood and stone jetties, not only shift sediment transport locally, but also shift system-wide sediment transport based on inlet-barrier island interactions and sediment partitioning. Better understanding these different modes of past evolution can help to guide coastal management strategies as beach nourishment increases in cost, sea level-rise accelerates, and extreme storm patterns change.

This work aims to investigate morphological long-term behavior in Babitonga bay inlet. A GIS tool was used to interpolate the bathymetric data from Empirical Bayesian Kriging model and generate the grided surfaces. The interpolated data from surfaces were analyzed through map algebra, depth isolines and cross profile comparison. The results indicate asymmetric trend in channel cross sectional area for the entire surveyed period, leading to shallower regions in the southeast bank and deeper regions in the northeast side. A depositional trend in ebb tidal delta was observed from 1940 to 1970 decade and a general loss was observed in ebb tidal delta from 1970-decade to nowadays, including the southern lobule. The results presented here, leads us to hypothesis that the bay and the adjacent ebb tidal delta may be in a natural starvation of sediment on a historic scale, that can be accelerated by the historical wave climate change and human interventions.

In this study, we use foraminifera as environmental indicators to aid in computing the historical volumetric inputs of estuarine sediments to adjacent marsh. These data can help assess the importance of estuarine sediment inputs to marsh accretion. The Grand Bay system (GBS), located on the southern coast of Alabama and Mississippi, has been described as a “self-cannibalizing bay-marsh complex” due to the disproportionately large amount of suspended sediment exported from the GBS relative to the amount of sediment imported into tidal channels and available to the marsh. Despite this sediment limitation in the marshes, mass sediment budgets along shoreline-proximal marsh sites suggest depositional fluxes on the marsh are nearly equivalent to erosional losses at decadal scales. Geochronologies and foraminiferal census data for two shore-normal transects show that estuarine sediment contributes significant portions (28-65%) of this depositional flux. Contrast in shoreline morphology (i.e., orientation, irregularity, and exposure) and adjacent environments (i.e., tidal creeks and mud flats) may influence the proportion of estuarine sediment delivered to marsh. Improvements of sediment provenance tracers in these environments will continually improve the understanding of sediment reworking and transport in transgressive marsh-estuarine systems such as GBS and the role they play in marsh resiliency to sea-level change.

Prediction of shoreline evolution in coastal environments is critical to aid adaptation strategy planning for coastal communities. To perform reliable predictions, process-based shoreline change models have recently gained popularity in many applications. The study region here, Tillamook County, Oregon, on the US Pacific Northwest coast, has recently been experiencing elevated shoreline erosion rates. The inherent uncertainties driving coastal change, e.g., sea-level rise and changing patterns of storminess, emphasize the need for robust shoreline evolution predictions in this region. To this end, we applied CoSMoS-COAST, an ensemble data-assimilated shoreline model that simulates short- and long-term shoreline change processes. We calibrated and validated the model using the hindcasted wave time series and observed shoreline positions and found a strong correlation between the number of observed shoreline positions and the model’s hindcasting skill. Moreover, results revealed an alongshore close-to-uniform shoreline change rate in the past several years, mainly driven by short-term, wave-driven processes. So far CoSMoS-COAST has performed satisfactorily with the spatially sparse supply of quality historical shoreline positions in our application. Moreover, this model resolves various components (e.g., short- and long-term processes) in the shoreline change sufficiently. This study represents a starting point in the long-term projection of shoreline evolution throughout the entire PNW (Oregon and Washington) coastline since Tillamook County features the majority of the coastal settings present in other coastal regions in the PNW.

Sandy coasts at the edge of inlet or estuary mouth often show the largest shoreline variability. However, previous work primarily addressed small-scale tidal inlets as time- and space-scales of morphological change make the system much easier to monitor. The aim of this study is to understand and quantify the controlling factors affecting shoreline change along the North Medoc Coast adjacent to the Gironde estuary mouth, SW France. Bathymetric surveys (1909-2021) and shoreline data from various sources (1940-2021) show that a massive estuarine sandbank welded to the shore in the early XX^th century. Since then, the bulge of sand has been diffusing alongshore, causing the shoreline to erode by up to ∼400 m over the last 80 years. This study suggests that it is critical to monitor bathymetric changes in such environments, to understand chronic erosion impacts on coastal infrastructures, to better anticipate future shoreline change and guide coastal management strategies.

This work describes the main evolutionary stages of the Sacalin barrier island developed in the last 125 years in relation to storminess variability, river supply, accommodation space and the morphodynamic feedbacks operating in association with big breaches occurrence. This deltaic barrier is highly mobile due to its low elevation and high wave and currents exposure, recording a continuous elongation (of ca. 150 m/yr) and progradation in downdrift sector (South Sacalin) but rapid retreat (20-70 m/yr) of the updrift sectors (North and South Sacalin). We found a contrasting behavior of the barrier characterized by fast shoreline retreat and small elongation during high storminess intervals but slight retreat and fast elongation during low storminess. Storminess is the main driver for the whole barrier together with the big breaches (only on the Central Sacalin) and the river supply which large amplitudes (i.e. floods) are transmitted via mouth bar volume to North Sacalin. Our analysis shows the key role played by storms in controlling the barrier evolution for all its sectors together with other controlling factors and mechanisms which act only locally.

This paper presents numerical simulations of long-term shoreline changes along regional-scale barrier islands around Absecon Inlet, New Jersey, using a shoreline evolution model. An idealized inlet reservoir model was developed to simulate inlet bypassing and volumetric changes of shoals and bars on the inlet morphology. The models were calibrated and validated by simulating shoreline changes and inlet bypassing of longshore sediment transport over a 16-years-long period. Simulations included historical coastal protection measures such as hard structures and beachfills. The validated model reproduced well the long-term shoreline evolution and the persistent erosion at the northeast end of Absecon Island. Numerical simulations of volumetric evolution of shoals and bars provide better understanding of sediment pathways through the inlet to the adjacent shores and the impact of shoal dredging.

Significant spatial gradients in tidal range often develop along marsh complexes and shallow estuaries due to bottom frictional dissipation of the tidal prism. Morphodynamic evolution and spatial tidal range gradients coevolve and constitute a strong positive feedback. We present simulations using a marsh landscape evolution model, MarshMorpho2D, coupled with a 1D model calculating tidal attenuation which depends on basin morphology. The model is capable of efficiently simulating long periods of time (10’s–1000’s yrs) at sub-annual morphodynamic timesteps. For larger tidal ranges (1.5 or 3 m) or a small tidal range with a short domain (< 10 km), tidal range decreases linearly landward at a small rate, barely impacting marsh platform elevations. Simulations with a microtidal range (0.7 m) and domain lengths greater than 10 km exhibit strong non-linear tidal attenuation. For these conditions, accurate long-term modeling requires a module for the dynamic evolution of tidal range gradients. Studying the long-term morphological evolution of this coupled system may elucidate interesting feedbacks. Significant temporal autogenic variability may emerge even under constant forcing conditions. Furthermore, changes in boundary conditions such as RSLR, sediment supply, or tidalshed length due to marsh upland migration may reveal a hysteresis with landscape response which is mediated by tidal dissipation. This model could also be applied to study the drivers of past and future landscape evolution at real world field sites with more precisely calibrated parameters.

In this study, we couple hydrodynamic, wave, and sediment transport models to study erosion of a sandy beach in Norfolk, Virginia, due to storm surge and sea level rise. Portions of the study beach are protected by detached breakwaters. The hydrodynamic+wave model (Delft3D) is validated with local tide and wave gauges and the sediment transport and morphodynamic model (XBeach) is calibrated with beach surveys. The model is then applied to study the response of armored and non-armored profiles to changes in mean sea level under, replicating sea level rise, under a hurricane scenario. Three beach profiles, one through a breakwater, one through a gap between breakwaters, and one over an unprotected stretch of the beach were selected for analysis. It was found that the beach transect through a breakwater exhibited the highest erosion, followed by the transect through a gap. The profile from the non-armored stretch showed the lowest erosion. Beach nourishment projects can benefit from this modeling framework to manage sediment resources in response to changing coastal forces.

Erosion of the Dungeness Bluffs in Washington, USA is a hazard to people in the area and is an important process in maintaining a healthy beach habitat. It is therefore critical to understand bluff erosion to ensure the safety of the people and coexist with species that rely on the process. Common methods in bluff erosion studies however are limited to changes observed from a bird’s eye perspective. To overcome this limitation, this paper uses field observations and difference point cloud datasets derived from boat-based LiDAR and structure-from-motion to analyze erosion and morphology of bluffs over the span of nine years. Our observations and results include changes difficult to capture in common methods such as erosion beneath overhangs and changes in bluff retreat due to lithology. When large failures from marine processes do not overpower subaerial processes, erosion rates along the face of bluffs are more apparent due to changes in lithology strengths. Talus materials fronting bluffs can disrupt marine processes and slow bluff erosion. Groundwater storage and springs can weaken bluff materials and cause sheet wash and shallow translational slides. Bluff morphology is tied to lithology because sharp changes in slope occurs along lithologic contacts. Moreover, retreating bluff profiles maintain similar shapes over time. Methods and results from this study are essential for coastal management, habitat evaluation, hazard recognition, and hazard mitigation around coastal bluffs.

The technological advances in remote sensing are well-suited for mapping in coastal settings. The quick mobilization of Unoccupied Aerial Systems (UAS) and/or small, 2-person, vessel-based acoustic surveys are ideal for extreme shallow water (<2 m) settings, such as low-energy embayments, estuaries and intertidal areas. Here we detail the use of these two modes of collecting spatial data in a very shallow water area for the purposes of developing a seamless topo-bathymetric surface. The total area mapped via UAS surveys and acoustic surveys was 2.8 and 2.2 km², respectively. The two surveys overlapped across 0.28 km², the acoustic data was used along most of that area. The study area has a mean tidal range of ∼3 m and the mean water depth during the acoustic survey was 2.16 m. It was shown that while the UAS could map areas faster and at greater resolutions, intertidal flats with standing water, or poorly drained sediment, made the UAS data of poorer quality than the acoustic data. In particular, these two systems complement each other well for the generation of seamless topobathymetric data sets in very shallow waters. Mapping of the coastal zone is most difficult at locations where either traditional marine or terrestrial mapping techniques are extended beyond their intended purpose, such as surf zones, very shallow waters or intertidal areas. It is critically important to map these areas as one system and the techniques discussed above are one way in which this can be done relatively inexpensively, but most importantly with some of the highest quality data possible.

The amount of wave and tidal energy entering an estuary from the ocean is highly influenced by the entrance morphology, therefore, the ability to accurately detect and measure bathymetric changes in morphology is highly desirable for coastal managers. As in-situ bathymetric data collection is often costly and/or logistically challenging, bathymetry derived from multispectral and hyperspectral imagery has become widely used. This paper details an ongoing investigation into the suitability of using UAV captured multispectral imagery to develop a repeatable methodology to detect and measure inlet morphological variability. Specifically, this study utilises multispectral imagery to derive bathymetric models using the empirical algorithm first proposed by Stumpf et al (2003) to determine inlet variability through time. This paper and presentation documents an ongoing field campaign of UAV multispectral imagery capture, the development of bathymetric models from this imagery and the validation of these bathymetric models using contemporaneous single beam sonar surveys. The study inlet, Moonee Creek, is on the south-east Australian coast and is a small, microtidal, wave dominated inlet. The ability to document inlet variability in a rapid and resource-effective way will help manage current and future challenges within estuarine systems and will help create more resilient communities. This study hopes to provide a methodology that will help understand the variability of coastal inundation under varying morphological entrance scenarios, which will support current and future coastal management decision making and planning.

Beach profile morphology studies have effective applications on erosion control and delimitation of areas susceptible to flooding and ecosystem protection. However, in situ measurements demand a significant amount of time and resources. A technique for reconstructing the surf zone and nearshore bathymetry from reflectance in satellite images is presented, using the combination of analytical equations. The methodology was applied to Gold Coast beaches, Australia, and at Campeche beach in Brazil. The bathymetric estimation errors were quantified by performing direct comparisons with in situ observations, showing that RMSE vary between 0.36 and 0.40 m and R² correlation values between 0.84 and 0.95. This methodology has shown some limitations, when estimating profile depths close to the depth of closure. The methodology proved to be satisfactory to represent beach profiles with bars in morphodynamic equilibrium. However, further research is required to deal with profiles that are out of equilibrium.

Shoreline evolution derived from optical satellite imagery is becoming key for monitoring sandy beaches, especially in locations where data are scarce. Here an improved methodology to obtain satellite-derived tidally-corrected shoreline position in macrotidal environments using the full tidal cycle is presented. This methodology is based on the CoastSat tool. The Belgian coast is used as a case study, where the methodology is validated using 9 years of LiDAR datasets. The validated algorithm is applied to extract and assess long-term trends of shoreline position along the entire coast for the period between 1984 and today. Accuracy has been assessed as satisfactory based on both the RMSE of satellite-derived to LiDAR-derived shoreline positions. Results of long-term shoreline evolution for the Belgian coast show realistic trends in line with anecdotal evidence linked to the presence of ports and the current coastal management strategy.

A method of observing both beach topography and the distribution of marine debris deposited on a coast using a UAV was developed. By this method, longitudinal profiles of the beaches, the distribution and number of deposited marine debris, and the change in ground elevation can be simultaneously determined. Field observations were conducted on 29 May 2021 before a storm and on 18 November 2021 after a storm at the Onuki coast south of Oarai Port, facing the Pacific Ocean. In this study, driftwood was adopted as a typical tracer of marine debris. Since driftwoods are transported on the sea surface, they deposit near a break in slope between the backshore and sand dunes during high tide and under storm wave conditions. The elevation range of the deposited driftwoods increased in response to the wave run-up height. These findings can help resolve the issue of excessive accumulation of marine debris onto Japan’s coast, especially with budget constraints.

Coastal sediments can vary in sediment properties over small spatial scales. The relationship between animals that inhabit these sediments and sediment properties is tightly coupled. Here we explore the transition from cohesive to non-cohesive sediments in the context of the forces that animals use to extend burrows by fracture. We use a new instrument developed to measure fracture toughness that applies tensile forces on small scales relevant for burrowing animals. We found a transition from non-cohesive responses to tensile forces in coarse sands to cohesive fracture in sands with only ∼10% mud content. This transition may be important in the mechanics of burrowing and the effects that burrowing animals have on sediment structure.

Distributed Acoustic Sensing (DAS) is an emerging technology for recording nearshore processes using fiber-optic cables. DAS measures cable strain, which is related to the pressure imposed by waves onto the cable, turning a cable into a dense array of wave gauges. Here, we present novel findings from one of the first applications of DAS to quantitatively measure nearshore waves. A fiber-optic cable was laid across-shore at the Field Research Facility in Duck, NC to quantitatively compare DAS strain to co-located wave gauges from Nov 2021 to Feb 2022. Significant wave height and peak period were accurately calculated from linearly converted DAS strain for a trial period in November. Wavelength was also accurately recorded by adjacent channels when the wave angle to shore was small. However, the linear DAS array recorded erroneous wavelengths with increasing wave angle, which can be corrected if wave angle is known. This work has demonstrated that calculations of spectra from DAS can provide accurate measurements of wave height and period. The strain signals recorded by DAS can be linearly converted to pressure under linear waves. Future work will focus on the development of a complete transfer function from DAS strain to pressure. Overall, this data provides promising insights into the potential for DAS to increase monitoring capabilities in the nearshore.

This paper describes the new tool of Coastal Analyst System from Space Imagery Engine a Collaborative Research Platform called CASSIE-CoRe, that is a cloud-based (using Google Earth Engine) web-tool which has a friendly and interactive interface that allows users to perform a distinct number of analyses at any given coastal environment around the world, using EO imagery and predictive tools. CASSIE-CoRe contains and manages six modules, two of which are in development phase (the Coastal-squeeze and topo-bathymetry modules) while one is fully implemented and operational: the Shoreline management module. It can be online accessed by any computer using a web-browser through https://cassiengine.org. The scalability of CASSIE-CoRe holds promise for managing growing and disorderly urban expansion in coastal areas which can impact the migration of coastal systems.

Observations of near-bed sediment suspension processes typically rely on a combination of acoustic and other ancillary sensors to monitor the dynamic suspended sediment environment. In addition to the suspended load, it is also of interest to quantify the settling and resuspension processes. Multi-frequency acoustic backscatter is an established technique for estimating vertical profile time series of mean particle size and concentration. Acoustic Doppler instruments are also used to measure water velocity intrusively at a single point, or in profiles of 3-dimensional velocity. Siting multiple acoustic instruments alongside one another can cause interference, leading to measurements having to be taken with either spatial or temporal separation. In this paper, we describe an approach for monitoring not only suspended load, but also parameters relating to settling velocity and turbulence in a single acoustic instrument with coincident beams. By exploiting the instrument’s capability to acquire a complex backscatter signal, profiles of the velocity of particles resolved along the acoustic beam can be calculated. When coupled with knowledge of particle size, this could be used to assess the density of the suspended particles and identify bubbles and flocs. Further statistical analysis of the velocity profiles has the potential to yield information about the turbulent kinetic energy dissipation rate over various length scales, which in turn can be used to assess the likelihood of floc formation. This has applications in science and industry, including observation of fundamental oceanographic processes, monitoring of coastal and civil engineering operations, and analysis of industrial processes.

During a 3-month deployment on a broad, fringing reef flat in Moloka’i, Hawai’i, we observed over 28,000 wave-driven resuspension (WDR) events of coarse-grained sediment in order to identify major factors. These events were short-lived (2-11 s) and distinct from the longer-duration patterns of water-column backscatter. The wave-driven transport of WDR events was onshore, but the net cross-shore transport was ultimately controlled by water levels. Higher water levels produced larger reef-flat waves, which were requisite for these events to occur. But rising water levels also drove stronger offshore flows. Consequently, onshore net transport of WDR events only occurred within a narrow water-level range, when waves were sufficiently large, but the offshore flow was still weak. Our observations demonstrate how cross-shore transport of coarse-grained material over reef flats is sensitive to changing water levels. Rising sea levels will likely alter transport patterns, which will in turn affect cross-shore delivery of carbonate sand to adjacent shorelines.

Considerable uncertainty remains in the budgets of carbonate sediment on reef lined coasts, particularly with respect to the supply of sediment to a reef flat that is then transported throughout a reef system. In this study, we re-examine two recent studies, one on a barrier reef bounded by channels that incise the reef, and one on a fringing reef without channels. Results indicate that the presence of channels results in a circulation regime that promotes not only the onshore sediment flux across the reef flat, but also upslope transport of sediment from the fore reef onto the reef flat. Data from these experiments suggest that when channels are present in the reef flat, the hydrodynamics of these reef systems favor the transport the transport of sediment up the fore reef. This outcome has implications for the design of potential reef restoration efforts intended to protect shorelines.

To help guide watershed restoration to reduce the impacts to adjacent coral reefs, the United States Geological Survey and Deltares acquired and analyzed oceanographic and sedimentologic data off 5 West Maui watersheds to calibrate and validate physics-based, numerical hydrodynamic and sediment transport models of the study area. The results indicated sheltered sites are impacted by terrestrial sediment from single stream mouths, with most of the sediment delivered within hours of a flood event. Once this sediment enters the nearshore, it settles out and remains on the reef for a prolonged period. In contrast, the coral reefs along “open” sections of coastline are more exposed to waves and terrestrial sediment from multiple stream sources and the terrestrial sediment can rarely settle but instead remains in suspension, causing turbidity. These analyses underscore the importance of understanding how hydro-dynamics can lead to different sediment dynamics on coral reefs in the same region.

A regional GENCADE model developed for the post-Hurricane Sandy Atlantic Coast of New York was used to investigate the shoreline evolution and sediment management implications associated with the construction and maintenance of three authorized projects over a 34-year time horizon. Combined the geographic extent of these projects encompass 84% of the oceanfront shoreline with interconnected transport pathways that modify how the barrier system responds to perturbations on varying temporal and spatial scales. Model results indicate the Long Beach and Rockaway projects independently stabilize the respective shorelines through 2054. The incorporation of FIMP within the regional system reduces some of the effectiveness of the Long Beach and Rockaway efforts. This is most likely the result of enhanced sediment trapping at Shinnecock, Moriches and Fire Island inlets associated with increased mining of the channels and ebb-shoals. For these three inlets proposed channel maintenance schedules and sand placement volumes may not be sufficient to stabilize the western shorelines for the next three decades. Natural feedback mechanisms through the littoral transport system demand a holistic assessment of project performance and the implementation of adaptive management strategies when necessary. The continued refinement and realtime updating of the regional GENCADE model is critical for proper management and increased understanding of the New York barrier system.

This paper describes a numerical study modelling the sediment transport due to the combination of waves, wave-driven currents and the ocean currents in the Gulf of Mexico. The model, which covers about 300 km of coastline is calibrated against measured water levels, currents and wave data. The sediment model predictions are verified against both observed bed level changes and dredging records from navigation channels. The results challenge previously published knowledge about the sediment transport along the Texas Coast. Current coastal management is based on the literature which focuses on wave-driven littoral drift as the driver of nearshore sediment transport. The work presented here shows that the interaction of waves and currents can lead to sediment transport in the opposite direction from the purely wave-driven littoral drift.

South Padre Island (SPI) is located on the southern Texas Coast. To improve understanding of regional sediment transport and assist the creation of a sustainable sand management plan, a numerical sediment transport model is developed to calculate nearshore sediment fluxes and analyze related sediment erosion/accretion patterns. The model results are validated by comparing with the measured data from field campaigns. The calculations illustrate annual and seasonal variations in mean current, wave conditions, and associated sediment transport. Storm waves generate strong longshore currents in nearshore area, which drive dominant longshore sediment transport. These findings provide insights for the South Padre Island BUDM (Beneficial Use of Dredged Material) program which aims to prevents beach erosion and mitigate shoreline retreat.

In this study, we focus on the effect of sand mining on the geomorphology of the San Francisco Bay within and beyond the mining locations. We do this by applying data-analysis techniques and efficient numerical modelling to assess volumetric changes and sediment transport pathways for the West-Central Bay area. Local and regional effects of sand mining were assessed by analyzing volumetric changes within six “ring areas” of high mining activity in West-Central Bay, as well as larger scale transport patterns and connectivity. The effects of aggregate mining were directly observed in the bed morphology by the presence of potholed areas. For most ring areas, the bed was significantly lowered, although particularly the southern rings show recovery of mined sand. The data seem to indicate that not only ring areas are affected by mining, but also adjacent zones. However, this could also be due to natural variations in forcing. Connectivity analysis based on transport pathway simulation can help identify regions of mining impact for varying forcing conditions. Sediment transport pathways inferred from bedform asymmetry and SedTRAILS simulations give insight into the connectivity between mining areas and the greater Bay area.

Hydrodynamic modeling was conducted to evaluate scour and deposition to determine potential mobilization of contaminants at Berth 17 in Port of Vancouver, USA. The goal of the study was to understand the surrounding river hydrodynamics and sediment transport at Berth 17 such as movements by ship traffic and vessel activity, dredging, and structure modifications such as pile removal in the neighboring areas. With the removal of upstream piles and clay ledge, velocities are increased along the bank, making the area upstream of the berth more erosive. However, the effects are minimal in the berth footprint during the 1-month extreme flow simulation. Furthermore, the effects of proposed Berth 17 maintenance dredging on sediment transport are negligible outside the berth footprint during the 1-month extreme flow simulation. Results show that hydrodynamic and sediment transport models provide valuable insight into the fate of contaminated sediment, and potential contamination of offsite areas based on mass of mobilized sediment and original contaminant concentrations. Results also show that dynamic simulation of scour due to vessel movements provide a much more realistic evaluation of sediment movements than empirical steady-state methods.

Headland bypassing is a wave-driven coastal process that interconnects sediment compartments and allows the continuity of the longshore sediment transport. Extreme storm events have the potential to generate waves that could trigger headland bypassing in some locations. In this study, a bypassing pulse resulting from a Tropical Cyclone passage along Queensland coast is investigated through topo-bathymetric surveys and numerical modelling of the hydrodynamic conditions. The headland bypassing occurred via a large offshore sandbar formed by strong southeast waves that enhanced the northward longshore sediment transport around the headland. This event caused substantial changes in the updrift and downdrift beach morphology, as well as delivered a significant sediment input for the beach compartment. Overall, this study demonstrates that identifying the storm events and quantifying their influence over generating headland bypassing pulses provides valuable knowledge for future sediment budget projections and, therefore, for local and regional coastal management.

This work details the US Army Corps of Engineers (USACE) Engineering Research and Development Center (ERDC) effort to generate lake-wide, near-seamless digital elevation model (DEM)s for Lake Michigan and Lake Ontario. The DEM product provides a key input for geomorphology feature extraction workflows; features include the dune and bluff toes and crests, sandbar features, and associated metrics for science and engineering studies. The mosaic dataset (MDS) architecture within ArcGIS Pro provides a means of fusing DEM datasets with varying sources, resolution and timeframes. The workflow includes filling data voids via interpolation and completing quality assurance and control measures on the final DEM to ameliorate artifacts from interpolation and fusion along dataset seamlines. The geomorphology feature extraction workflow and the development of associated metrics is accomplished using the Dune Feature Extraction module of the JALBTCX Toolbox (Dong et al., 2018) using a transect-based methodology. These features and metrics provide critical inputs to a GLRI-led Geomorphic Vulnerability Index (GVI) development effort and the USACE Coastal Engineering Resilience Index (CERI) for Lake Ontario. This is a critical path for delivering timely elevation and bathymetry updates to coastal engineers and scientists for use in their applications and studies.

Barrier-island beaches and tidal inlets are valuable coastal resources and dynamic landforms. They behave as one interconnected barrier-inlet system and must be understood and managed as such. Beach-inlet interaction is complicated, driven by both wave and tidal forcing, and occurs at multiple temporal and spatial scales. The interaction can be illustrated via sediment pathways and quantified with a balanced sediment budget. Regional sediment management (RSM), a systems approach with adequate temporal and spatial scales, constitutes a fundamental modern philosophy in shore protection and restoration. Beach-inlet interaction and sediment pathways play an essential role in the RSM of barrier-inlet systems, a key physical aspect of coastal resilience. This paper reviews the present understanding on beach-inlet interaction and sediment pathways at barrier-inlet systems, and the temporal scales of their morphodynamics, for applications of RSM A RSM decision-making framework including the formulation of a sediment budget is discussed with a case study of a barrier-inlet system in west-central Florida. A systems approach incorporating adequate temporal and spatial scales is essential for modern beach protection and restoration. Understanding and quantifying sediment bypassing, associated pathways and the temporal scales of their morphodynamics are key to the management of tidal inlets and adjacent beaches. Managing sediment resources at a regional scale through a balanced sediment budget constitutes a major component in coastal resilience building.

High-resolution geodetic GPS elevation measurements at 20 benchmarks were used to determine recent subsidence velocities for Terrebonne Basin. Elevation change time series encompassed approximately 5- to 17-year periods. Water elevation change from four gauges in the southern part of the basin supplemented survey data, resulting in a range of subsidence velocities at 24 locations from approximately 3 to 8 mm/yr. In the northern half of Terrebonne Basin, where Holocene deposits range from 30 to 45 m thick, subsidence velocities range from 3 to 5 mm/yr. The area is characterized by the oldest deposits of the Teche and Lafourche delta complexes. A distinct zone of broken marsh and lakes south of Houma marks the northern boundary of the 5 to 8 mm/yr subsidence zone in southern Terrebonne Basin, where Holocene deltaic sequences are thickest and youngest to the south and east, resulting in overall greater consolidation potential. Understanding the causes and rates of subsidence across the Louisiana coastal zone is critical to successful planning and implementation for State Master Plan projects.

Lakeshore changes due to high-wave angle instability were investigated in Lake Inawashiro in Fukushima Prefecture, Japan. On the north shore of this lake, the shoreline runs approximately parallel to the direction of predominant waves incident from the west, causing the development of shoreline undulations. The shoreline evolution was investigated through the comparison of satellite images. It was found that the mean eastward moving velocity of a sandbar was 68 m/yr between 2010 and 2015. Then, the movement of the sandbar was reproduced using the BG model (a model for predicting three-dimensional beach changes based on Bagnold’s concept). As a result, the moving velocity of the sandbar predicted in the numerical simulation was in good agreement with the 68 m/yr observed between 2020 and 2015.

The wetlands of the eastern Bird’s Foot Delta (BFD) located in southeast Louisiana have experienced severe degradation over the past several decades. The primary cause of wetland loss in this area is the combination of relative sea level rise and decreased hydrologic connection to the Mississippi River, which results in insufficient sediment deposition and increased salinity. The BFD restoration project proposes to restore the hydrology and improve the freshwater and sediment delivery to the eastern portion of the delta through dredging efforts. To inform restoration efforts, we performed numerical modeling to evaluate hydraulic and morphological patterns across the BFD. This involved using 2-D and 3-D models to resolve the natural distribution of flows at Head of Passes, and the complex feedback this flow distribution has on the geomorphology and hydraulic performance of adjacent distributaries, crevasses, and crevasse splays. We found that including 3-D processes and resolving crevasse splay feedback is paramount in properly answering the project questions.

The present study focuses on a quantification of the morphologic evolution of the Zackenberg delta in North-East Greenland. The time scale of this evolution ranges between days, events and decades. The study describes the impact of extreme discharge events on the delta morphology (delta plain and delta front) and schematize the fluxes of sediment and morphologic change between the different parts of the active and abandoned delta lobes. The extreme river discharges cause the main changes on the active delta lobe leading to channel shifts. Besides, average river discharges transport sediments to the fjord and can locally lead to lateral channel migration on the delta plain. Wave action dominates the changes on the abandoned delta where a spit migrates on the delta plain and partly closes the inner delta plain for wave action. This creates a salt marsh close to the former Zackenberg distributary. A conceptual sketch summarizes the fluxes of sediment and morphologic change between the different parts of the active and abandoned delta lobes. These findings bear insights on extreme events in Arctic coastal environments with impacts including damage of local infrastructure on delta plains.

Accurate sediment monitoring in rivers is important in coastal processes. Since direct sediment sampling is practically laborious, researchers rely on regressionbased approaches for the littoral cell sediment budget analysis. In this study, we present a support vector regression-based real-time sediment load monitoring total sediment load monitoring method that uses the signals of an acoustic Doppler current profiler system. Using the sediment monitoring method, the contribution of bedload for five months was assessed by comparing the suspended and total loads. The result suggested the significance of bedload contribution in the sediment supply (especially single flood event).

This study presents the results of the sediment accumulation rates and sediment properties analysis performed on a core from Roșuleț. Lake, in the maritime compartment of the Danube delta. Based on radiochronology (¹³⁷Cs and ²¹⁰Pb measurements) and carbon content (TOC, IC, and TC) assessment, the sediment accumulation rates covering the last ca 160 years have been computed using the CRS function. Further, the elemental content determination provided insight into the depositional environment settings (i.e., eutrophication, oligotrophic states) and depositional processes. The main two peaks in MAR and MiAR coincide with the dramatic human intervention episodes in the Danube delta: the channel cuttings program after 1940 and the construction of the Sulina-Sf. Gheorghe channel and dyke during 1989-1995. The dyke construction essentially blocked seaward water circulation from the Roșu-Roșuleț lake system, resulting in increased eutrophic conditions. Understanding the response of a deltaic system to future environmental changes requires complex and accurate empirical data on past sedimentation rates of various compartments of the deltas.

This study presents the first assessment on bathymetric and emerged land changes in the Atchafalaya Bay from 1935 to 2012. This study utilized bathymetric data from 1935 and 2012 in the Atchafalaya Bay to quantify the subaerial and emerged land changes. The study also used satellite images from 2014 to 2016 to assess the recent deltaic growth. We found an average annual sediment trapping of 3.21 million cubic meters from 1935 to 2012, equivalent to approximately 4.49 MT of sediment in mass. The Atchafalaya River subdelta captured 61% of the total, but its growth stagnated in the recent years, while the Wax Lake Outlet subdetla continued growing. We quantified a current volume of 597.53 million m3 from the water surface to the seafloor in the Atchafalaya Bay, which suggests that 836.54 MT of sediment will likely be needed to completely fill in this bay. Considering the largely-reduced sediment delivery from the Atchafalaya River (< 5 MT/yr sand) and the rapidly rising sea level in the coming decades (> 1 cm/yr), new land building in the bay would drastically slow down or even decline. Such knowledge is crucial for understanding the land building process as well as for predicting their future growth

The use of generalized wave parameters from spectral models in wave climate, sediment transport, and coastal evolution assessments is of common practice despite this parametric description of waves is inaccurate describing sediment transport magnitude and direction under multimodal waves. In this study, we explore sensitivity arising from considering multimodal waves to assess wave-driven sediment transport on the Dutch shoreface. First, we analyze the spatio-temporal wave spectrum field in the North Sea, discern wave partitions, and statistically aggregate them into wave families. Then, we calculate and compare sediment transport following traditional methods and based on wave partitions and wave families. Finally, we discuss sensitivity on annual transport capacity. We find that long-perioded wave fields can significantly increase sediment transport and should therefore be considered next to the more energetic short waves. On the Dutch shoreface 65% of the time waves are multimodal, and these can contribute significantly to annual transport capacity. This study shows how models might overcome the difficulty faced by traditional models in predicting the magnitude and direction of sediment in multimodal wave conditions.