Analysis of Sea-Level Rise Impacts on Sea Dike Stability in Hai Hau Coast, Vietnam

Climate change and global warming have led to severe typhoons and sea level rise (SLR) which may threat the stability of coastal structures. However, countermeasures to enhance coastal protection against SLR and severe typhoons have not appropriately considered. The Hai Hau coast with 33.3 km of sea dikes is located in the Red River delta of Vietnam. Herein, coastal dikes have collapsed twice over the last 30 years, which lead to about 1.5 km of coastline retreat. This paper aims to assess quantitative impacts of SLR on sea dike stability. Change in pore water pressure (PWP) in the dikes was monitored by piezometers. Distribution of PWP at different tide levels was then used to calculate factors of safety (Fs) of inner and outer slopes. Projected SLR until 2100 will reduce Fs of the outer slopes, but sea dikes have no problem with sliding stability. The main threats of SLR to sea dike stability are indirect impacts such as accelerated erosion, scouring, and wave overtopping-induced soil erosion on the inner slopes. Troughs of sea dikes in Hai Hau coast could fail in 6-10 years due to accelerated coastal erosion. A solution of multiple protections to adapt to SLR in Hai Hau coast was proposed which includes conventional structures (i.e. dike, revetment, groins, and mangrove) together with geotubes as submerged breakwaters and vetiver grass.