A system of shallow water equations and a bed evolution equation are used to examine the evolution of perturbations on an erodible, initially plane beach subject to normal wave incidence. Both a permeable (under Darcy's law) and an impermeable beach are considered. It is found that alongshore-periodic morphological features reminiscent of swash beach cusps form after a number of incident wave periods on both beaches. On the permeable (impermeable) beach these patterns are accretional (erosional). In both cases flow is ‘horn divergent’. Spacings of the cusps are consistent with observations, and are close to those provided by a standing synchronous linear edge wave. An analysis of the processes leading to bed change is presented. Two physical mechanisms are identified: concentration gradient and flow divergence, which are dominant in the lower and upper swash respectively, and their difference over a wave cycle leads to erosion or deposition on an impermeable beach. Infiltration enters this balance in the upper swash. A bed wave of elevation is shown to advance up the beach at the tip of the uprush, with a smaller wave of depression on the backwash. It is found that cusp horns can grow by a positive feedback mechanism stemming from decreased (increased) backwash on positive (negative) bed perturbations.Postprint (published version
Thailand was hit by a great flood in 2011 resulting from irregular rainfall during the typhoon season that was estimated at 140% more than average. The flood began in the north and slowly moved to the central region, where it remained for more than 4 months. The flood caused great damage to the economy because it adversely affected industrial estates and agricultural areas. In the north, there are four main rivers in the region that combine into a river called Chao Phraya in the central region. The Yom River is one of the northern rivers where no large-scale dam has been constructed, resulting in frequent flood and drought. Sukhothai Province is located in the Yom Basin, where flood and drought occur on a regular basis, and the province was also severely damaged in the 2011 flood. In order to estimate flood damage cost in 2011, a simple regression curve is presented first to relate flood areas and damage cost based on past records. The 2011 flood in Sukhothai province was then simulated by using a Rainfall-Runoff-Inundation (RRI) model with satellite based rainfall (TRMM). After simulation results were compared with the observed stream flow water level, discharge and inundation extent, this study estimates damage cost for the 2011 flood based on the simulated flood area. The proposed approach could be a useful guideline in damage cost computation.
Abstract. This study evaluated the potential of coastal trees to reduce flooding areas caused by waves with abnormal heights, such as storm surges, using a numerical model applied to idealized beaches. The study considered 5 factors that affect sensitivity of coastal areas to flooding: slope of the beach, bottom friction coefficient, length of tree lines, width of tree lines, and shape of tree areas. The results indicate that slope of the beaches can reduce flooding areas, as steep slopes can transform wave energy into potential energy. With regard to the friction coefficient, beaches with higher bottom friction factors will have fewer flooding areas. Relative to beaches with no trees at all, increasing the length and width of tree lines can reduce flooding areas by as much as 30%. However, the shapes of tree areas have no significant effect on flooding areas.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.