Tidal Flood Model Projection Using Land Subsidence Parameter in Pontianak, Indonesia

Abstract

Land subsidence is a phenomenon that can exacerbate the impacts of tidal floods in coastal areas, such as disrupting citizen activities, and submerging settlements and public facilities. Therefore, research on tidal floods and their relation to land subsidence was widely studied in coastal areas of Indonesia. However, this study has not yet been carried out in the Pontianak, a dense urban area located in the Kapuas River Delta, West Kalimantan Province. This study aims to analyze the impacts of land subsidence on tidal floods in the city for disaster mitigation and long-term urban planning. We calculated the land subsidence by applying the DInSAR technique to Sentinel-1A imagery. Then, tidal floods were simulated by integrating the DELFT3D hydrodynamic and HEC-RAS hydraulic models. The results showed that the output water level of the DELFT3D model has good agreement with the observation data, which the Nash Sutcliffe Model Efficiency Coefficient (NSE) is 0.83. Furthermore, the maximum land subsidence in Pontianak is ± 1.03 cm/year, where the highest subsidence (between 0.48 -1.03 cm/year) covers about 28.54% of the total area. Our results showed that shallow inundated areas (water depth less than 0.5 meters) decreased by 23.6%, while deep inundated areas (water depth more than 0.5 meters) increased by 16.9% over the next 50year. Overall, the depth of the tidal floods within Pontianak that occur in the future will increase by 0.03-0.4 meters and varied in across locations. These analysis results can guide the local water manager in designing a mitigation plan.

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