Assessing multi-decadal shoreline change and future sea level projections to support coastal adaptation in Selangor, Malaysia

Coastal zones are increasingly exposed to climate change and rapid urbanization, yet the geomorphological stability of tropical, mud-dominated coastlines remains poorly understood. This study evaluates multi-decadal shoreline dynamics along a 250 km corridor of the Selangor coastline, Peninsular Malaysia, from 1990 to 2020. Using seven multi-temporal, sensor-homogenized Landsat datasets, baseline change metrics were computed via the Digital Shoreline Analysis System (DSAS v5.1). Historical shoreline shifts were quantified using the End Point Rate (EPR) and Linear Regression Rate (LRR) metrics to construct a process-based Geomorphological Stability Index (GSI). These historical vectors were coupled with IPCC AR6 sea-level rise anomalies to simulate scenario-based exposure projections for the 2030, 2040, and 2050 horizons. Baseline results revealed severe localized erosion hotspots exceeding -75 m/yr near the highly engineered Port Klang complex. The EPR network yielded a net erosional tendency of -0.15 m/yr, whereas the LRR model revealed a marginal net accretionary trend of +0.30 m/yr. The GSI framework classified 53.19% of the transects as highly stable/accreting (Rank 5) and 32.92% as severely eroding (Rank 1). Validation against an independent hazard inventory demonstrated a framework sensitivity of 100.0%. Scenario-based projections reveal intensifying erosive trends by 2050, accelerating mean EPR erosion to -5.14 m/yr and destabilizing up to 49% of the shoreline footprint. The findings provide actionable screening data to guide climate adaptation strategies.