Shoreline change rate and erosion risk assessment along the Trou Aux Biches–Mont Choisy beach on the northwest coast of Mauritius using GIS-DSAS technique

Abstract

The present study investigates the rate of shoreline change and erosion risk along the Trou aux Biches–Mont Choisy beach in the northwest coast of Mauritius using digital shoreline analysis system (DSAS). In this analysis, the long-term shoreline change rate and coastal erosion and accretion pattern are estimated along the coastal stretch using multi-temporal aerial photographs and high resolution satellite images for the past 45 years (1967–2012). The shoreline change rate and erosion/accretion pattern at each transects are estimated by five statistical parameters functionalized in DSAS 4.5 software such as end point rate (EPR), shoreline change envelop (SCE), net shoreline movement (NSM), linear regression rate (LRR), and least median of squares (LMS). The measurement of shoreline change rate and coastal erosion and accretion pattern has been described for three segments namely (1) North–North–West (NNW) to South–South–East (SSE); (2) North–East (NE) to South–West (SW); (3) North–North–East (NNE) to South–South–West (SSW) based on the coastal configuration. The analysis reveals that the severe erosion risk (−1.75 to −0.03 m/year) was noticed between transects 41 and 61 in NE–SW segments and moderate erosion risk (−1.09 to −0.18 m/year) between transects 62 and 95 of the NNE–SSW segments. The NNW–SSE segment shows low erosion risk with an EPR value of −0.55 to −0.05 m/year. The values of shoreline change rate of these transects indicate the occurrence of severe erosion along the coastal area over the periods of 1967–2012. However, the coastal segment in NNW–SSE configuration faces least erosion rate and the protective coral reefs reduce the wave energy action which leads to the formation of sustainable coast in the area. Moreover, poor set back and management activities with reference to high energetic waves, storm surge and cyclonic conditions produce direct impacts on the coastal morphology and degradation of coral reef ecosystem. The shoreline change studies through integrated remote sensing and GIS technology is considered of paramount importance for accurately focusing on planning, management and coastal intervention in long-term purpose.