Abstract
The hydro- and morphodynamic processes within the Vietnamese Mekong Delta are heavily impacted by human activity, which in turn affects the livelihood of millions of people. The main drivers that could impact future developments within the delta are local stressors like hydropower development and sand mining, but also global challenges like climate change and relative sea level rise. Within this study, a hydro-morphodynamic model was developed, which focused on a stretch of the Tien River and was nested into a well-calibrated model of the delta’s hydrodynamics. Multiple scenarios were developed in order to assess the projected impacts of the different drivers on the river’s morphodynamics. Simulations were carried out for a baseline scenario (2000–2010) and for a set of plausible scenarios for a future period (2050–2060). The results for the baseline scenario indicate that the Tien River is already subject to substantial erosion under present-day conditions. For the future period, hydropower development has the highest impact on the local erosion and deposition budget, thus amplifying erosional processes, followed by an increase in sand mining activity and climate change-related variations in discharge. The results also indicate that relative sea level rise only has a minimal impact on the local morphodynamics of this river stretch, while erosional tendencies are slowed by a complete prohibition of sand mining activity. In the future, an unfavourable combination of drivers could increase the local imbalance between erosion and deposition by up to 89%, while the bed level could be incised by an additional 146%.
Highlights
The Vietnamese Mekong Delta (VMD), which is home to approximately 18 million people, is essential to the food security of Southeast Asia
In order to quantify the impacts of different drivers shown in Table 2 on the morphology of the study area, the resulting erosion and deposition patterns, tendencies of bed level incision and balances between erosion and deposition volumes were analysed in relation to the baseline scenario
The model was nested into a well-calibrated hydrodynamic model of the whole
Summary
The Vietnamese Mekong Delta (VMD), which is home to approximately 18 million people, is essential to the food security of Southeast Asia. The construction and operation of hydropower infrastructure within the Mekong River. Basin (MRB) has led to a significant reduction of sediment supply to the delta region. 32% of the total basin-wide sediment load, was trapped within the MRB caused by the operation of hydropower dams [9]. MRB, with 212 additional dams having been commissioned [10]. Should all dams be built, the sediment supply to the South China Sea could be reduced by more than −95% [2,3]. In addition to a reduction in sediment supply, the construction and operation of hydropower dams within the MRB alter the monsoon-driven hydrological regime [11,12,13,14] and hinder fish migration [15]
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