Narrow Results

This paper investigates the concept of modeling cliff stability and collapse during extreme erosion events using a hybrid model method combining Weakly Compresible Smoothed Particle Hydrodynamics (WCSPH) with a particle based geotechnical stability module (GeoSPH). The WCSPH model has been developed to include a sediment transport and morphological model to predict erosion of a beach slope under a wave climate. The GeoSPH model is based on a displacement stepping method and due to its particle nature it sidesteps the mesh straining and distortion that hinders many traditional models. The model concept and future research direction is investigated and the initial results of erosion and collapse in a storm event are presented. Conventional methods of bluff collapse are often probabilistic, based on extrapolation bluff retreat rates, or reliant on an equilibrium profile, and as such struggle to adapt the predicted movement when changes occur to either the bluff or to the wave climate. Using a hybrid model of wave-driven erosion and bluff stability allows for site by site analysis and can be run without any data of past events.

In this paper, results of sediment transport at Exe Estuary, Devon, UK, obtained from a process-based model under a number of wave and tide scenarios, are presented. This study uses a nested modelling system, which consists of an oceanic scale wave model WAM and a tide/surge model POLCOMS, to transform the meteorological information to nearshore wave and tide conditions for a fine resolution local coastal process-based model to carry out detailed predictions of nearshore hydrodynamics and morphodynamics at the study area. The work is focused on studying the impacts of yearly and 1 in 50 year return period storm events on morphology at the mouth of the Exe Estuary and the adjacent coasts. Comparisons of model results are made with the beach survey data carried out by the local authorities in March 2008, in addition to the model tests on both yearly calm and storm conditions in November 2006.

Numerical simulations of hydrodynamics and sediment transport were conducted for Sebastian Inlet, FL, using the Coastal Modeling System (CMS). The study is aimed at determining changes in morphology under the existing topography and configuration as compared with two proposed modification scenarios: 1) an extension of the south jetty and 2) dredging of the outer section of the ebb shoal. The analysis time period encompasses short term (storm vents), as well as long term (seasonal). Overall, the predicted morphology changes were in good agreement with measured data. Model calculations of littoral sand transport under the existing configuration indicated an overall sand transport to the south over the long term, as well as reversal approximately 2km south of the inlet. The model also successfully reproduced the variability in littoral transport due to the different storms, especially the reversal in the drift direction.