Linking rapid erosion of the Mekong River delta to human activities

Abstract

As international concern for the survival of deltas grows, the Mekong River delta, the world’s third largest delta, densely populated, considered as Southeast Asia’s most important food basket, and rich in biodiversity at the world scale, is also increasingly affected by human activities and exposed to subsidence and coastal erosion. Several dams have been constructed upstream of the delta and many more are now planned. We quantify from high-resolution SPOT 5 satellite images large-scale shoreline erosion and land loss between 2003 and 2012 that now affect over 50% of the once strongly advancing >600 km-long delta shoreline. Erosion, with no identified change in the river’s discharge and in wave and wind conditions over this recent period, is consistent with: (1) a reported significant decrease in coastal surface suspended sediment from the Mekong that may be linked to dam retention of its sediment, (2) large-scale commercial sand mining in the river and delta channels, and (3) subsidence due to groundwater extraction. Shoreline erosion is already responsible for displacement of coastal populations. It is an additional hazard to the integrity of this Asian mega delta now considered particularly vulnerable to accelerated subsidence and sea-level rise, and will be exacerbated by future hydropower dams.

Carbon dynamics and CO<sub>2</sub> and CH<sub>4</sub> outgassing in the Mekong delta

“…In addition, sediment river delivery could also vary in response to changes in climate (Västilä et al, 2010;Lauri et al, 2012;Darby et al, 2016). This would have important consequences on the sediment deposition in the delta that seems to have already shifted from a net depositional (accretion) regime into a net erosion regime (Anthony et al, 2015;Liu et al, 2017). The nutrient inputs to the continental shelf from the Mekong delta sustain high phytoplankton growth in the Mekong River plume (Grosse et al, 2010), which is one the most productive areas of the South China Sea (Liu et al, 2002;Qiu et al, 2011;Gao et al, 2013;Loisel et al, 2017).…”

Carbon dynamics in the Mekong Delta

“…In addition, sediment river delivery could also change in response to changes in climate (Västilä et al 2010;Lauri et al, 2012;5 Darby et al, 2016). This would have important consequences on the sediment deposition in the delta that seems to have already shifted from a net depositional (accretion) regime into a net erosion regime (Anthony et al, 2015;Liu et al, 2017). Koné and Borges (2008) …”

Sustainable rice cultivation in the deep flooded zones of the Vietnamese Mekong Delta

“…The VMD is vulnerable to environmental changes, such as with the size and timing of floods and droughts, sea-level rise, and saltwater intrusion, which come as a result of climate change and human modifications to the Mekong River's basin upstream [2]. These environmental changes, combined with local development pressures, represent significant threats to the Delta, such that the VMD is now facing a major sustainability challenge [3]. Among the most serious of the expected impacts is the ongoing decline of the Mekong River's sediment load.…”