Shoreline Change and Coastal Settlement Planning in Selected Niger Delta Communities

Shoreline change poses a major geomorphological and planning challenge for densely settled estuarine communities in the Niger Delta, where fluvial discharge, tidal processes and human activities continually reshape the land–water boundary. This study examines multi-decadal shoreline dynamics along the Sombreiro River in the coastal communities of Abonnema, Degema and Idama and evaluates their implications for coastal settlement planning. Shoreline positions for 2005, 2010, 2015 and 2020 were extracted from medium-resolution satellite imagery and analysed using the Digital Shoreline Analysis System (DSAS) version 6.1. Shoreline change was quantified using the Shoreline Change Envelope (SCE), Net Shoreline Movement (NSM), End Point Rate (EPR), Linear Regression Rate (LRR) and Weighted Linear Regression (WLR). Results reveal pronounced spatial variability among the three communities. Abonnema experienced moderate but persistent erosion (LRR = −0.75 m/yr), while Degema recorded the most severe and spatially variable retreat (LRR = −2.07 m/yr), with a mean SCE of 81.82 m and maximum shoreline recession of 74.58 m. In contrast, Idama exhibited dominant accretion (LRR = +0.73 m/yr), with approximately 70% of transects showing shoreline advance. The comparatively greater stability of Abonnema may reflect existing shoreline protection measures and favourable local geomorphological conditions relative to Degema. The close agreement between LRR and WLR confirms the internal consistency of the historical shoreline dataset despite uncertainties associated with image resolution, tidal variation and shoreline extraction. The study recommends integrating DSAS-derived shoreline information into coastal settlement planning through risk-based development setbacks, targeted shoreline protection, ecosystem-based management, conservation of vulnerable waterfront corridors and community-based land allocation strategies that discourage future residential development within erosion-prone areas. Periodic field validation and higher-resolution monitoring are also recommended to strengthen future shoreline-management decisions.