Study of shoreline evolution under the influence of jetty construction: A case study of Karangsong Beach, Indramayu, Indonesia

Abstract

Karangsong Beach, Indramayu located on the north coast of Java Island of Indonesia has been an important traditional small downstream river port for the fishermen who live in the Indramayu District area. This traditional port has been rehabilitated by construction of jetty in the period 2005 to 2007. The jetty construction affected coastal process, which was previously dominated by erosion turned into dominated by accretion. This study examines the process of shoreline evolution by calculating the sediment transport rate and analyzing the shoreline changes. The analysis began by extracting shoreline data from Google Earth images to provide a historical database of shoreline. The coastal process was then simulated using the coastline model Uniform Beach Sediment Transport Coastline (UNIBEST-CL) with waves and the longshore component of tidal currents as input and also calibrated using the shoreline database. The calibrated model was employed to simulate the annual conditions over a nine-year period, 2008-2017. The results show the sediment transport rate is dominated by the southeast direction. There is a significant difference in coastal processes between northern and southern regions, which is due to the presence of jetty. In the northern region, the sediment transport rate was blocked by the jetty so that this region is accreted. In the southern region, the supply of sediment from the north replaced by sediment supply from the river causes accretion yet smaller than the northern region.