Author(s): Annisak Laila Rakhmawati; Ali Dastgheib

Linked Author(s): Annisak Laila Rakhmawati

Keywords: Compound flooding; Hazard modeling; SFINCS; Land subsidence; Climate adaptation

Abstract: This study applies a multi-driver, scenario-based flood modeling framework to evaluate compound flood hazards in Pekalongan City, Indonesia, a coastal urban area experiencing accelerated land subsidence and exposed to concurrent pluvial, fluvial, and coastal flooding processes. A total of 19 scenarios were developed to represent various combinations of flood drivers, including extreme rainfall, river discharge, tidal levels, projected sea-level rise, and subsidence rates under 10- and 100-year return periods. Simulations were conducted using the SFINCS (Super-Fast INundation of CoastS) model, which solves reduced shallow water equations and is optimized for large-scale, high-resolution flood modeling in low-gradient coastal systems. The results indicate that compound events produce significantly greater flood extents, depths, and durations than single-driver scenarios. Scenarios involving simultaneous rainfall, river discharge, and coastal forcing under future sea-level and subsidence conditions resulted in the highest impacts, with inundation affecting up to 69% of the city, maximum depths exceeding 3.5 m, and durations surpassing 96 hours. Land subsidence consistently amplified both horizontal flood spread and vertical water accumulation, even under moderate meteorological conditions. These findings highlight the critical importance of integrated, multi-driver hazard assessments in urban flood risk management. The scenario-based methodology provides a transferable tool for evaluating present and future flood hazards, supporting evidence-based decision-making for adaptation planning in data-constrained, climate-vulnerable regions.

DOI: https://doi.org/10.64697/978-90-835589-7-4_41WC-P1922-cd

Year: 2025