Coastal Engineering Journal

The paper presents an analysis of 40 years of measurements of geographic location (longitude, latitude) and power (wind speed) of tropical storms and typhoons over South-East Asia seas, mainly the South China Sea and the Philippine Sea. The results demonstrate the growing intensity of duration of the most severe events. The analysis includes singular spectrum analysis of wind speed series in the period 1960–2000 to identify two sub-periods of roughly similar behavior. Then, the recorded events and occurrences are classified statistically. The most extreme ones from the 1st and 2nd sub-period are plotted as functions of their geographic co-ordinates to assess the spatial evolution of their location. Next, the escalating power and mostly duration of the most extreme typhoons are examined with extreme probability distributions to quantify the resulting climate change consequences in the studied region. Finally, all results are reiterated in the form of conclusions and suggestions for potential follow-up research.

A combined model was built of three main modules based on the Volume of Fluid (VOF) method, Discrete Element Method (DEM), and Finite Element Method (FEM). It was proposed to utilize this model to simulate the deformation of the rubble mound and the sandy bed due to surface wave action. The model included the full interaction between wave motion with free surface and replaceable separate particles of the rubble mound. Momentary arrangement of the fluid, particles and resulting permeability was tracked within a domain of time and two-dimensional space by maintaining cyclic data transfer between the three method modules. A new technique of porosity adjustment was presented. The model results were compared to small-scale laboratory test results. Based on the comparison, the VOF-DEM-FEM model appeared to be a promising tool to handle the destruction process of the rubble coastal structures built on a permeable bottom.

Fragility functions, as new measures for estimating structural damage and casualties due to tsunami attack, are developed by an integrated approach using numerical modeling of tsunami inundation and GIS analysis of post-tsunami survey data of the 2004 Sumatra–Andaman earthquake tsunami disaster, obtained from Banda Aceh, Indonesia. The fragility functions are expressed as the damage probabilities of structures or death ratio with regard to the hydrodynamic features of tsunami inundation flow, such as inundation depth, current velocity and hydrodynamic force. They lead to the new understandings of the relationship between local vulnerability and tsunami hazard in a quantitative manner.

To understand the influence of laver aquaculture facilities on the current system and sediment transport in Ariake Bay, field experiments to measure the hydraulic resistance and velocity distribution of a compartment of an aquaculture facility were conducted with numerical simulations of the hydrodynamic environment and suspended particulate matter (SPM) dynamics in local areas around aquaculture facilities and those in the bay scale. The results of the field experiments showed that the resistance coefficient of laver aquaculture nets varied from 0.01 to 0.02, depending on the quantity of laver. The resistance of the nets and poles per a compartment of laver aquaculture facility was of the same order of magnitude as bottom friction, but differences in temporal variation were observed during a tidal cycle. The surface velocities were reduced downstream from the aquaculture facility because of the resistance of the laver nets, and the thickness of this surface boundary layer was approximately 1 m at the downstream end of the facility. The numerical simulation of the head of Ariake Bay showed that the tidal currents and SPM concentrations were reduced in the laver farming ground area, whereas they were increased in the water channel regions because of the relative differences in hydraulic resistance.