Infrastructure effects on floods in the Mekong River Delta in Vietnam

Abstract

The Mekong River Delta (MRD) is one of two primary rice-growing areas in Vietnam. Flooding in the Mekong River is a recurrent event and is not only one of the most destructive natural disasters but also a natural resource in this area. The cultivated surface soil layer in the Mekong Delta has a thickness of only about 50 cm, and is heavily polluted by acidic water infiltrating from deeper soil layers during the dry season. The annual floods carry fertile silt to farmland and fresh water to wash away the acidic water and provide the water needed to grow vast rice fields. The flood water carries with it various fish species that facilitate aquaculture development in the area. The floods also wash away polluted water and provide the whole delta with clean water.Owing to these different factors, the flooding in this area has a positive impact on agriculture and a negative impact on regional planning. Recent infrastructural changes designed to mitigate flood damage and protect crops and residents' lives make the inundation regime more complicated. To understand the role of infrastructure in the flood regime in this area as well as the mechanism of the flood regime, it is necessary to apply an integrated method of study including numerical modelling, a geographic information system (GIS), and statistical analyses. This study includes a brief presentation of the measured data analysis of flood variation trends over the 43-year period from 1961 to 2004 and an analysis of the hydrological effects of infrastructure changes associated with human activities in the period from 1996 to 2001 based on the integrated hydraulic model known as HydroGis.

Simulated Impacts of Climate Change on Current Farming Locations of Striped Catfish (Pangasianodon hypophthalmus; Sauvage) in the Mekong Delta, Vietnam

“…Hoa et al (2007) predicted that ''The future flood control works planned to be completed by 2010 will cause an increase in runoff peaks and prolong the duration of the flood recession. '' In general, the present study confirms that three sea level rise scenarios will lead to an increase of the water level in the rainy season and to an expanded salinity intrusion in the dry season both at spatial and temporal scales in the Mekong Delta, Vietnam, thus increasing the vulnerability of the delta area to climate changes (Wassmann et al 2004;Khang et al 2008;Hoa et al 2008). Syvitski et al (2009) presented an assessment of 33 densely populated and heavily farmed deltas globally and estimated the delta areas vulnerable to flooding could increase by 50 % by sea level rise in the twenty-first century.…”

“…We assessed the impacts of water level and salinity intrusion along the Tien and Hau branches of the Mekong river in time and space by applying model-based scenarios for sea level rise and reduced river flow (e.g., Alcamo et al 1998;Wassmann et al 2004;Hoa et al 2007Hoa et al , 2008Khang et al 2008). …”

“…Specifically, the VRSAP model was used by Wassmann et al (2004) to map the vulnerable rice production areas and by Nguyen and Savenije (2006) to predict the salinity distribution in the Mekong river branches using topography, tide, and river discharge data. Hoa et al (2007Hoa et al ( , 2008 used an integrated hydraulic model, HydroGis, in tracking the impact of sea level rise and flooding in general. Khang et al (2008) simulated changes in water flow and salinity intrusion for two sea level rise scenarios (?20 and ?45 cm) by using the MIKE11 model and a GIS.…”

Assessing impacts of dike construction on the flood dynamics of the Mekong Delta

“…South of Vam Nao, the water volumes of the two rivers become more balanced, owing to interconnecting tributaries. Due to the delta's flat, low-lying topography (its average elevation is just 0.8 m above mean sea level) and the impact of tidal regimes (Hung, 2012), the annual floods inundate 1.2 to 1.9 million ha of the delta (Hoa et al, 2008; Kingdom of the Netherlands and the Socialist Republic of Vietnam, 2013). In a severe flood season, water depths reach up to 3 m, affecting the lives of more than 2 million residents.…”

“…Hoa et al (2008) used the HydroGIS hydrodynamic model to evaluate the effects of the infrastructural changes from 1996 to 2004 on floodwater levels and flood protection efficacy. They concluded that infrastructure works, such as dredging canals, raising embankments, and upgrading roads, likely mitigated the overall extent of flooding but increased flood depth by 20 to 30 cm in some regions near and between embankment systems.…”