Numerical Study on Measures for Protecting the Go-Cong Coastlines (Vietnam) from Erosion

Abstract

Every year, in the Vietnam Mekong Delta Coastal Zone (VMDCZ), erosions cause approximately 300 ha of agricultural land loss. Therefore, measures for shoreline protection are urgently needed. This paper discusses the impacts of protection measures in the Go-Cong Coastal Zone to prevent erosion/accretion processes, predicted by two numerical models, MIKE21-FM and TELEMAC-2D. Hard and soft measures have been proposed using breakwaters and sandbars, respectively. The simulations show that the erosion/accretion trends provided by both models are similar. For breakwaters, MIKE21-FM provides less accretion than TELEMAC-2D in areas extending over 300 m and 500 m from shorelines. However, for sandbars, MIKE21-FM shows higher accretion within areas extending over 500 m but less than 300 m. Sandbars cause higher accretion in a larger area, extending over 1000 m offshore. The simulation results allow us to propose two alternative measures: (1) a row of several breakwater units will be implanted at 300 m offshore. The length of each unit is 600 m, with a gap between two neighbouring units of 70 m and a crest elevation of 2.2 m above mean sea level (MSL). (2) A row of sandbar units will be posed at 500 m offshore, with a unit length of 1000 m and a gap between the two neighbouring units of 200 m. The crest elevation is fixed at MSL.

Morphological Evolution of an Intertidal Mudflat in Relation to Mangrove Growth: Implications for Future Erosion Control

“…The findings indicated that fine-grained sediment accumulated as US in the first stage of the morphological evolution of Ngang Island. The sediment accumulation that occurred was partly due to the area experiencing low-energy activities, as previously reported [60,[66][67][68][69]. Sediment accumulation increased steadily and subsequently expanded the shoreline, as shown in Figures 3 and 4.…”

“…Currently, the planting of mangrove plants has been prioritized by the existing coastal erosion control measures (for example, ecological engineering—mangrove planting—and engineered solutions for the construction of shoreline and offshore protection structures) to establish intertidal mudflats and stabilize eroded coastal areas in Southeast Asia [ 63 , 64 , 65 ], including Vietnam [ 48 , 66 , 67 , 68 , 69 ]. However, the opposite is true, as shown in Figure 3 , Figure 4 and Figure 6 (1) of this study.…”

“…The tidal range varies between +1.8 and +2.2 m [ 61 ]. To date, much information is available related to the hydrodynamics and sedimentation conditions of the Tan Phu Dong district, which includes Ngang Island [ 66 , 67 , 68 ].…”

“…This knowledge is important, particularly in contexts where mangrove forests are believed to trap sediments and contribute to the progradation and aggradation of deltas [ 61 , 62 ]. In addition, the existing coastal erosion control measures (ecological engineering solutions—mangrove transplantation—and engineered solutions—construction of shoreline and offshore protection structures) emphasize the utility of planting of mangrove seedlings in an attempt to trap sediment to establish intertidal mudflats and stabilize eroded coastal areas in Southeast Asia [ 63 , 64 , 65 ], including Vietnam [ 48 , 57 , 66 , 67 , 68 , 69 ].…”