Study on the response and recovery of beach sediments under the impact of Typhoon “Chaba” (no. 2203) and high-elevation aquaculture pond effluent discharge

Under the combined influences of climate change and human activities, coastal sediments dynamic and recovery mechanisms following extreme storm events have become central issues in coastal research and management. This study investigates beach sediment dynamics and recovery processes under the joint effects of Typhoon No. 2203 “Chaba” and high-elevation aquaculture pond (HEAP) effluent discharge. The key findings are as follows: Typhoon forcing conditions: During the event, wind direction shifted from ES to N and wind speed rose from 6.46 m/s to 14.43 m/s, superimposed on a 4.18 m storm surge. The mean wave period and significant wave height rose to 7.34 s and 1.38 m, respectively, while the shear-stress due to waves surged from 0.20 to 4.20 N/m²—far exceeding the threshold shear-stress of 0.60 N/m². On the normal beach, typhoon events led to finer sediment deposition on the upper beach and coarser sediment on the lower beach. These changes rapidly returned to the pre-typhoon state within one week. On the impacted beach, typhoon events and aquaculture effluent significantly altered sediment distribution. Combined effects of effluent-driven morphology and hydrodynamics caused complex patterns and limited recovery. Effluent discharge, tidal action, and wave dynamics collectively establish a high-energy conduit system that extends the landward reach of tidal inundation and intensifies erosion at the beach berm and coastal dune front. This synergistic forcing underlies the rapid evolution of scour-trench and grain-size distributions during extreme events. Therefore, it is recommended to implement coordinated strategies in terms of drainage outlet placement, ecological protection measures, and management practices. These measures aim to promote harmony between aquaculture and the beach environment, ensuring sustainable ecological and economic development.