Exploring shoreline changes and their implications in coastal communities using GIS and remote sensing techniques: The case of eastern beaches of Unguja island, Tanzania

Abstract

Understanding shoreline dynamics and their impacts is crucial for the successful planning and development of coastal regions. This study focused on the research scarce area of the eastern coast of Unguja island, Tanzania to explore shoreline changes and their implications from 1990 to 2040 using GIS and remote sensing techniques. Four Landsat imagery taken in 1990, 2000, 2010 and 2020 were obtained and processed to determine past shoreline scenarios using Net-Shoreline-Movement (NSM), End-Point-Rate (EPR) and Linear-Regression-Rate (LRR) metrics in the DSAS software. Additionally, the LRR and the Kalman filter model were employed in the same software to determine future shoreline scenarios up to 2040. Overall results by LRR demonstrate that the shoreline of the eastern coast of Unguja was eroding at an average rate 15.560 m/year and its erosion rate is projected to reach 25.648 m/year by 2040. The total land eroded and accreted by EPR was 37,540,702.71 m² and 734,721.8037 m2, respectively. Periodically, high shoreline erosion rates occurred between 2000 and 2010 by the NSM (529.926 m, −798.133 m and −65.230 m) and EPR (53.299 m/year, −78.884 m/year and −6.617 m/year) results. Geographically, our study has identified that a significant portion of shoreline erosion occurs in the northern part of the island and some of its main identified impacts include the destruction of facilities along the coastal zone area. These findings call for the immediate and long-term interventions to mitigate adverse impacts of shoreline erosion and can inform other research in similar areas.