Spatio-temporal shoreline assessment of a dynamic deltaic coast: integrating DSAS and ecological indices for Konark Coastal Belt, India (2005–2025)

Abstract

The Konark coastal belt, a morphodynamically active segment of the Mahanadi deltaic system, is undergoing rapid shoreline transformation driven by the interplay of sea-level rise, altered wave regimes, and intensifying anthropogenic pressures. This study aims to present 20-year spatio-temporal assessment (2005–2025) of shoreline dynamics across three morphodynamically distinct segments at Gop, Kakatpur, and Astarang using multi-temporal Landsat imageries, Digital Shoreline Analysis System (DSAS) metrics, and ecological indices. This study focuses on long-term shoreline dynamics; cyclone and extreme event influences were not explicitly considered. DSAS analyses showed peak erosion of − 3.87 m/year at Kakatpur and accretion up to + 3.12 m/year near Gop, with long-term retreat averaging − 2.14 m/year across erosion zones, and + 1.98 m/year in accreting areas. The results reveal pronounced accretion in Kakatpur (0.59 m/year), moderate gain with erosion hotspots in Gop (0.15 m/year), and highly variable dynamics in Astarang (2.8 m/year). Despite net progradation, spatial heterogeneity is evident with 20.55 to 33.71% of transects experiencing erosion. Ecological indices demonstrate substantial ecosystem transition, with vegetated areas expanding from 38% to 69% with 5,899.2 ha, and soil fertility improvements over 3,256.9 ha, while moisture-dominated zones declined from 42% to 27%, indicating accretional sediment-vegetation feedback mechanisms. Kalman filter-based predictive modelling projects shoreline retreat of up to − 16.5 m in erosion hotspots by 2035 and − 32.3 m by 2045, with uncertainty ranges of ± 10 m to ± 24 m across zones specific evolution scenarios with RMSE validation demonstrating acceptable forecast reliability (± 18.17 m overall). The integration of DSAS metrics revealed strong correlations between rate-based estimators (r = 0.997), validating methodological consistency. The findings provide a zone-specific decision-support framework for coastal resilience, hazard mitigation, and habitat restoration, transferable to comparable deltaic systems globally.