Comparison between averaged and localised subsidence measurements for coastal floods projection in 2050 Semarang, Indonesia

This paper uses a raster-based inundation model (LISFLOOD-FP) to simulate coastal flooding using the major causes of coastal inundation i.e. extreme water levels and subsidence combined with rising sea level. Specifically, this study uses sea level scenarios through 2050, projected by linear estimation of the Semarang tide gauge record from 1997 to 2015. In addition, we calculated extreme water levels along Semarang, Indonesia, using the modern extreme value theory introduced by Gumbel (1958) and Jenkinson (1955). Simulations of coastal flooding show that subsidence in Semarang may be the leading reason that coastal flooding is getting worse, followed by sea level rise (SLR). Compared to the average subsidence scenario, the scenario with SLR projection and subsidence interpolated based on the local measurements in the research area by 2050 shows the highest flood volume with an increase at 1,483,251 m3 and a flood area increased by up to 1.5 km2 (6.8 increase). The same impact events happened regarding the widest extent of extreme criteria of flood hazard that employs an increase at 11.5 km2 (287 increase) and rose by 3 km2 (35 increase) compared to the average subsidence through 2050. © 2020 Elsevier B.V.