Mangrove ecosystems are important resources in the coastal region that provide physical, biological, social and economic functions. However, these ecosystems are highly affected by coastal dynamics, including the processes of abrasion and accretion that can be caused by ocean waves, wind, or human activity. Among the areas that has suffered damage due to abrasion over the past 20 years is the coastal area of Subang district in West Java. The objectives of this study was to describe the changes in coastline and mangrove forest area from year 2000 to 2018 in that area. This study is important as it provides an overview of the dynamics of the coastline as well as the decline in mangrove area that has occurred over the past 18 years; thus becoming a reference in the formulation of policies on mangrove rehabilitation.

The study area encompasses 2,830.24 hectares of coastal area in Legonkulon sub-district in Subang district. Identification of shoreline changes and mangrove vegetation was carried out using the on screen digitating technique in ArcGIS software 10.5.1. Shoreline change was calculated by overlaying Landsat 7 ETM + imagery in 2000, 2003, 2006, 2009, 2012 and Landsat 8 OLI images in 2015 and 2018 along 8,837.6 m coastline using the DSAS (Digital Shoreline Analysis System) program version 5. Mangrove parameters were measured in the form of area and level of greenness through calculation of the NDVI value (Normalized Difference Vegetation Index). The results of this study indicate that since 2000 to 2018, the coast of Subang district has experienced a change in coastline by the process of accretion and abrasion. In general, the level of damage in the coastal area of Legonkulon is classified as severely damaged with a damage rate of more than 88.29% of the total coastal length. Abrasion has occurred as far as 1,216.13 m, with an abrasion rate of 67.56 m/year, and a maximum abrasion of 5,903.66 m. Accretion has occurred as far as 0.6 m, with an accretion rate of 0.03 m/year, and maximum accretion as far as 58.71 m. Mangroves in Legonkulon sub-district in 2000 were dominated by canopy density levels in the rare category and has experienced an extensive loss of 767.70 hectares since 2000 to 2018.

Keywords: shoreline, mangrove ecosystem, abrasion, accretion, DSAS