Monitoring Shoreline Changes in the Vietnamese Mekong Delta Coastal Zone Using Satellite Images and Wave Reduction Structures

This study aimed to assess the current state of the shoreline and the effects of erosion on the shoreline in Vinh Chau Town, Soc Trang Province, Vietnam. Satellite image overlays were used to quantify the variation in the shoreline as a result of erosion caused by changes in wave action. In addition, the wave measurements were implemented at three representative shoreline protection sections (sea dike, mangrove forest belt, and the breakwater) to evaluate the wave height reduction at the shoreline. The results showed that erosion affected approximately 23 km (32%) of 72 km coastline of the study area. The erosion penetrates the land area from −16.9 to −3.0 m/year (Landsat images) and −11.68 to −7.95 m/year (Google Earth images); the coastline recession increases every year, leading to the gradual loss of mangrove forests and also farmland. The wave measurement shows the effectiveness in wave height reduction of the mangrove forest and the constructed breakwater to protect the sea dike. Wave height reduces more than 50% when passing through the mangrove forest belt, corresponding to a maximum height (Hmax) of 62.3%, 1/10 Hmax at 55.3%, and 1/3 Hmax at 54%. For the constructed breakwater, the wave reduction efficiencies recorded due to Hmean are 72.18% and 1/10 Hmax are 73.16% and reach 72.47% with 1/3 Hmax. The results are based on wave measurement over a short time period; thus, it is not possible to conclude about the wave reduction efficiency of the current measures in the long term. It is necessary to monitor continuously and with different wind seasons to have a more accurate assessment of wave reduction efficiency.