Assessment of coastal vulnerability to support mangrove restoration in the northern coast of Java, Indonesia

The northern coast of Java has been more severely affected by sea level rise (SLR) than other islands in the Indonesian archipelago. This warrants a coastal area risk assessment to ascertain the multiple hazards that could impact on this densely populated island. Using environmental and physical variables – including geomorphology, rate of shoreline change, sea level rise, wave height, coastal slope, bathymetry, tidal range, and mangrove density – the main objective of this study is to determine a coastal vulnerability index (CVI) and mangrove vulnerability index (MVI) in the northern Javanese coastline. Assessment was carried out for three regencies – Banten, Demak, and Banyuwangi regency – with the goal of helping to identify areas where mangrove restoration efforts can be prioritized. Using line and 1 × 1 km2 grid representation of the entire coastline, the research found that in terms of CVI, Demak coast is most vulnerable (with 82% of grids and 89% of coastline falling into the highly vulnerable categories), Banten coast ranked as moderately vulnerable (43% of grids and 35% of coastline fall into the moderately vulnerable categories), while 91% of grids and 93% of coastline in Banyuwangi fall into the least vulnerable category. Assessment of mangrove vulnerability revealed that Banten and Banyuwangi regency were low vulnerability as respectively, 100% and 94% of grids fell into this category, while Demak coast was highly vulnerable (with 46% of grids falling into highly vulnerable categories). This vulnerability mapping provides useful information to assist planners and managers to deploy resources for mangrove restoration and the long-term sustainable management of these coastal ecosystems.