Dikes are not native to the Mekong Delta in Vietnam. Historically, this region functioned as a natural depression, absorbing floodwaters from the Mekong during the rainy season and releasing them during the dry season. The construction of dikes to contain floodwaters has enabled the cultivation of a third rice crop annually, thereby increasing the yearly rice yield. However, this comes at a cost. Building dikes in the upper delta to produce a third rice crop has unintended consequences downstream. The dikes force the floodwaters into narrower channels, increasing their speed and causing greater erosion and flooding damage in the middle and lower delta, extending all the way to the sea.
In following figure, comparison of peak river water levels at stations along the Hau River resulting from different flood years (Duc Tran et al, 2018)
