Assessment and management of coastal erosion: Insights from two tropical sandy shores in Mauritius Island

摘要

Rising sea level and increasing tropical storm frequency caused by the changing climate are threatening small Island economies which depend on their coastal environments and resources. Owing to the high socio-economic and environmental values of tropical sandy beaches, monitoring the evolution trends of shorelines are regarded as an essential strategy to improve the resilience of Island states. The present study conducted in Mauritius, indi- cates a net erosional effect at Le Morne amounting to 8049.7 ± 5% m~2 which is attributed to the hydrodynamics of the lagoon, whilst a net accretional effect has been observed at Flic-en-Flac, equivalent to 6571.3 ± 5% m~2 and attributed to periodic beach nourishments. The shoreline evolution at Le Morne is predominantly influenced by Passe de la Prairie where an average energy of 0.162 m~2/Hz, corresponding to an average wave height of 1.16 m, carries enough energy and momentum to influence the sediment transport near the peninsula. At Flic-en-Flac, longshore currents propagating on either sides of the central region and directed northwards and southwards influence the shoreline, resulting in an accretion zone extending 62.5 ± 15 m near Villa Caroline over the 2009-2018 period. To dampen this problem, a beach management strategy is proposed which revolves around the restoration of corals in front of eroded shores, replacement of casuarina trees, and enforcement of regulatory laws.