Assessing cross-shore coastal erosion processes in Bạc Liêu, Vietnam
S.A. de Wit (TU Delft - Civil Engineering & Geosciences)
Dirk S. van Maren – Mentor (TU Delft - Environmental Fluid Mechanics)
Z. B. Wang – Mentor (TU Delft - Coastal Engineering)
More Info
expand_more
Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.
Abstract
As part of the Mangrove Living Lab project, this research examines how multiple drivers influence coastal erosion in Bạc Liêu, Vietnam. Currently, observed erosion in this region cannot be explained by natural sediment redistribution, and literature suggests that tidal flows are more cross-shore dominated in Bạc Liêu compared to adjacent provinces. Consequently, four key anthropogenic drivers that primarily act in the cross-shore direction are explored: (1) land subsidence due to increased groundwater extraction, (2) reduced sediment availability, (3) foreshore degradation leading to higher waves, both induced by fluvial sediment deficit, and (4) the construction of sea dikes and fishpond dams in the intertidal zone, resulting in tidal flow restriction, wave reflection and coastal squeeze.
Two main methods are applied: a cross-shore elevation level analysis to assess spatial differences in subsidence and sediment supply, and a numerical model to assess the influence of each driver individually and combined. The elevation analysis revealed that subsidence varies spatially along the coast. Moreover, historic satellite images show that a site without subsidence has been accreting in the past, while a site experiencing subsidence remained stable during the same period. After 2004, they both began eroding. This suggests that differences in subsidence rates largely explain spatial variations in current coastline positions, while the erosion itself is likely driven by additional drivers. However, the limited spatial and temporal coverage of elevation transects highlights the need for more extensive data collection. Numerical modeling indicates that reduced wave heights and increased suspended sediment greatly reduce erosion rates, and can even overshadow the effect of subsidence when combined. This demonstrates that historic and ongoing fluvial deficit is likely the main driver of the current erosion. The role of intertidal structures remains inconclusive due to model limitations and differing theoretical interpretations. Refining the current model or developing more advanced alternatives will help improve understanding of these coastal erosion processes. This is needed to support the development of integrated solutions that protect both the communities and ecosystems of Bạc Liêu.