Reconstructing and forecasting the shoreline dynamics of coral reef islands in the Saudi Arabian Gulf: integrated remote sensing and automated computational techniques

Erosion of coral reef islands is a critical geomorphic and environmental challenge in semi-enclosed basins such as the Arabian Gulf, where hydrodynamic forcing is highly variable. However, predictive modeling of future shoreline evolution remains lacking for the Jana and Karan Islands. To address this knowledge gap, this study quantifies historical shoreline dynamics and forecasts the future morphological evolution of both islands. Multi-temporal remote sensing imagery was used to digitize shoreline positions from 1965 to 2026. Offshore baselines were established around both islands, and perpendicular transects were automatically generated at 4 m intervals using the Digital Shoreline Analysis System (DSAS v5.1). Historical shoreline change rates were quantified using Net Shoreline Movement (NSM), End Point Rate (EPR), Linear Regression Rate (LRR), and Weighted Linear Regression (WLR). Model performance was first evaluated through hindcast validation. In this step, the Kalman filter was calibrated using the historical shoreline record prior to 2026. The forecast 2026 shoreline was then compared with the independently observed 2026 shoreline using mean squared error (MSE), root mean squared error (RMSE), and the correlation coefficient (r). Following this validation, the resulting LRR rates were integrated with the Kalman filter to forecast shoreline positions for 2046. Historical observations (1965–2026) for Jana Island show a persistent erosional trend, resulting in a net areal loss of 37,933 m² despite 3557 m² of accretion. In contrast, Karan Island exhibits highly heterogeneous morphodynamics, yielding a net areal gain of 55,411 m² alongside substantial erosion of 21,931 m². Forecasts through 2046 indicate ongoing erosion on Jana Island, with an additional net loss of 9897.12 m². In comparison, Karan Island is projected to sustain its accretional trend, achieving a net gain of 29,263.49 m² despite 3398.51 m² of erosion. Validation of the Kalman filter showed strong agreement between the forecast and observed shoreline displacements. For Jana Island, the overall RMSE was 5.35 m with a correlation coefficient of r = 0.96, while Karan Island yielded an RMSE of 2.13 m and r = 0.99. These divergent shoreline trajectories are consistent with variations in wave exposure, tidal currents, and bathymetric configurations within the complex hydrodynamic regime of the Arabian Gulf. Overall, these findings indicate that Jana Island is considerably more vulnerable to sustained land loss than Karan Island. This underscores the need for targeted shoreline monitoring and adaptive coastal management to mitigate erosion and protect coastal habitats and the ecosystem services they provide.