Quantifying 28-year (1991–2019) shoreline change trends along the Mnazi Bay – Ruvuma Estuary Marine Park, Tanzania

Abstract

Over the last decades, shoreline movements observed at the Mnazi Bay - Ruvuma Estuary Marine Park (MBREMP) in Tanzania have been affecting habitats' conditions and also social and economic conditions of local communities. To date, however, there has been no systematic spatial and temporal analysis of shoreline change trends along the MBREMP coast.In this study, we conducted an analysis of multi-temporal earth observation satellite imagery for assessment of MBREMP shoreline change trends, over the period 1991–2019, using satellite images and geographic information system techniques. Satellite images retrieved from Landsat 5 (Thematic Mapper) and Landsat 8 (Operational Land Imager) instruments were analyzed within a geographic information system environment. Shorelines were extracted from satellite imagery and shoreline change rates were measured along transects using the Digital Shoreline Analysis System (DSAS) software.From the analysis performed over the period of 28 years, we concluded that shoreline changes in MBREMP were dominated by erosion with an average erosion rate of −1.5 m/year ±1.4 m/year. No-shoreline change (stable shoreline) was identified in 34.8% of transects analyzed, erosion in 63.9%, while accretion occurred in 1.3%. The extent of erosion and accretion varied, however, from one area to another. Accretion and lower erosion rates were measured in the northern part of MBREMP, while higher erosion rates were found in the southern part of the park, which serves as important feeding, breeding, and nesting habitats for endangered turtle species.These results do contribute to identify the most affected areas of MBREMP shoreline and to inform and guide further research related to the sustainable management of ecosystems and the maintenance of the natural systems/resources contained in the park.