Morpho-hydrodynamic processes impacted by the 2022 extreme La Niña event and high river discharge conditions in the southern coast of West Java, Indonesia

Abstract

The significance of sediment-laden river discharges is strongly related to climate change and rainfall intensity, resulting in severe erosion of the catchment areas and riverbanks. The combination of tides and waves considerably influence the sediment transport and distribution patterns of an estuary, inducing the sedimentary processes of the coastal area. This study aims to analyze the impacts of the La Niña event in 2022 and high river discharges in the Bojong Salawe Beach, Pangandaran. This area has a large estuary with several tributaries, with a high potential for erosion and sedimentation. Furthermore, its location directly faces the Indian Ocean, posing the risk of wind-induced high waves. The methods used in this research are descriptive analysis (using dataset ERA-5 taken from the Copernicus Climate Change Service) and numerical models (using Mike21) with an identification of erosion and accretion processes. The results show that the boreal autumn 2022 significantly impacted the study area, compared to the boreal winter 2022. Higher precipitation levels during boreal autumn substantially increased the river discharges, transferring the total load of sediment of about 1.48 m3/s/m. Moreover, shoreline change analysis using digital shoreline analysis system confirmed that Bojong Salawe Beach was indicated to experience high erosion, particularly around the mouth of the estuary.