NON-STATIONARY ANALYSIS OF WIND-DRIVEN, NEARSHORE CURRENTS AND BEACH EROSION CHANGES IN NANGOKU CONSTRUCTION AREA OF KOCHI COAST CAUSED BY 24 STORMS FROM 2011 TO 2019

Abstract

 The Kochi coast facing the Pacific Ocean has a beach process characteristics in which the beach collapse due to abnormal typhoon waves and the beach reforming due to normal wave power are balanced in the erosion-deposition phase changes. In this paper, we focus on the erosion phase of the beach changes in the Nangoku construction area of Kochi coast due to abnormal wind and waves. A numerical analysis was conducted to reproduce the coastal erosion mechanism for the 24 major storms from 2011 to 2019. The beach change process is simulated with a sediment transport model formed by wave-current coexisting model in shallow water where the offshore sediment transport caused by undertow can’t be neglected. The developed sediment transport model is tuned from the results of topographical changes in multi-narrow beam depth sounding surveys. The effects of beach protection measures of the Nangoku construction area was evaluated from the point of view of sediment control by the coastal structures scheduled.