Multi-scale modelling for hydrodynamic and morphological changes of breakwater in coastal Mekong Delta in Vietnam

Coastal erosion has been occuring at a rapid rate in recent years along the Vietnamese Mekong coastline with particularly significant impacts occurring in the Tan Thanh – Go Cong coastal area. This erosion issue poses an urgent need for rapid deployment of offshore breakwaters for coastal protection and to reduce the severity of incoming waves. This objective of this study is to apply a multi-scale numerical model (MIKE21-FM) to evaluate the impact of breakwaters on hydrodynamic behavior and morphological changes in the coastal zone. The results from the numerical model simulations showed that breakwater stuctures can effectively reduce the velocity and height of incoming waves by over 50%. The results also showed that the breakwater structures lead to increased sediment accumulation, even during the Northeast monsoon season, when strong waves and currents can occur. Our results indicated that construction of a sufficient number of breakwaters is crucial to increase the efficiency of the breakwaters as well as the protection coverage of the coastline. Finally, the results showed that the longer construction is, the wider coastal area it can protect to stimulate accretion.