This study aims at evaluating the geographical influences of rice-based protection dykes on floodwater regimes along the main rivers, namely the Mekong and the Bassac, in the Vietnamese Mekong Delta (VMD). Specifically, numerous low dykes and high dykes have been constructed particularly in the upper delta’s floodplains to protect the double and triple rice cropping against the annual flooding. For the whole deltaic domain, a 1D-quasi-2D hydrodynamic model setup was used to simulate seventy-two (72) scenarios of dyke construction development in the context of low, medium, and high floods that occurred in the VMD to examine the effects of different flood magnitudes on a certain dyke construction area. Based on the model simulation results, we established an evaluation indicator, the so-called Geographical Impact Factor (GIF), to evaluate the impacts of zone-based dyke compartments on the floodwater regimes along the main rivers for different kinds of floods. Our findings revealed different rates of influences on the floodwater levels along the Mekong and Bassac Rivers under different scenarios of zone-based high-dyke developments. GIF is a useful index for scientists and decision-makers in land use planning, especially in rice intensification, in conjunction with flood management for the VMD and for similar deltas worldwide.

Rural areas and rural livelihoods in many countries have been affected by changes in natural and environmental conditions. In areas where livelihoods relied on the floodwater, changes in flood regimes and the natural environment had significantly impacted many farmers' livelihoods. In the Mekong Delta flooded areas, flood patterns changed mainly due to the hydropower development and the climate change. The livelihoods of many farmers, primarily rice farmers, were facing challenges and needed changes to adapt to the sustainable livelihood development. This study used a sustainable livelihood framework of DFID to assess factors affecting the sustainability in agricultural livelihoods in flooded areas of An Giang province, specifically at Phu Hiep and Phu Long communes of Phu Tan district. We interviewed 60 farmers based on the structured questionnaire and conducted two focus group discussions with more than 40 participating farmers. Our results of the Livelihood Capitals Index (LCI) showed that natural and physical capitals had less impact on household livelihoods. Phu Long is less affected than Phu Hiep by assessing five capitals. Farm households' current livelihoods were mainly affected by the lack of human resources and the unstability of market prices. The rate of consensus on transition to sustainable farming models was not high due to many factors. However, the transition is possible if their production and output are secured by the government.