Numerical Simulation on the Change of Bottom Topography by the Presence of Coastal Structures

This paper presents a numerical model for predicting the change of bottom topography caused by coastal structures placed on a sandy beach. The model consists of three sub-models of wave transformation by varying topography and coastal structures, nearshore current and change of bottom topography. The computation of nearshore current patterns induced by the presence of a detached breakwater shows qualitative agreement with the experiment. The effects of wave and structure characteristics on current pattern and topographical change are investigated by consideration of model computation with several configurations of coastal structures such as detached breakwaters or groins. The main conclusions are that the model produces the general features of erosion and deposition caused by coastal structures and that drastic change of current pattern and bottom topography occur when reflected waves from the structures cover a large area.