Land subsidence is a natural phenomenon in delta systems. Deltaic sediments are highly compressible and susceptible to significant natural compaction during deposition and subsequent soil formation. Enhanced land subsidence in deltas due to human activities is widely recognized (e.g. Syvitski et al., 2009; Giosan et al., 2014). Human use of land and groundwater resources can amplify natural subsidence processes or initiate new anthropogenic subsidence in different ways (Galloway et al., 2016).
In the Mekong delta evidence of widespread absolute subsidence was recently revealed by InSAR (Interferometric Synthetic Aperture Radar) (Erban et al., 2013, 2014). Minderhoud et al. (2017) demonstrated that a steady increase of groundwater use and excessive pumping over the past decades has dramatically accelerated subsidence in this area. For more detailed information click here: link
After 7,500 years of natural fast increasing land accretion and steady propagation to the southeast, this trend has been reversed in the years 2005 to 2018. More than 50% of the 720-kilometre coastline is eroding – of which more than 10% is eroding at between 20 and 50 metres per year. The loss of forest land along the coast is particularly sensitive since this green belt was once stabilising the dynamic silty coasts by attenuating wave surge and trapping fine sand and clay. Erosion of the entire tidal mudflats leave deep scours and steep embankments where natural mangrove resettling is impossible.
In a region where one rice field and shrimp pond borders the next, the loss of land to the sea by erosion means that economic and social pressures multiply. Developing an appropriate strategy to mitigate and adapt to these changes has become crucial.
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