Long-term sediment decline causes ongoing shrinkage of the Mekong megadelta, Vietnam

Type Article
Date 2020-05
Language English
Author(s) Tamura Toru1, 2, Nguyen Van Lap3, Oanh Ta Thi Kim3, Bateman Mark D.4, Gugliotta MarcelloORCID5, Anthony Edward J.6, 7, Nakashima Rei1, Saito YoshikiORCID1, 5
Affiliation(s) 1 : AIST, Geol Survey Japan, Tsukuba, Ibaraki 3058567, Japan.
2 : Univ Tokyo, Grad Sch Frontier Sci, Kashiwa, Chiba 2778561, Japan.
3 : VAST, HCMC Inst Resources Geog, Ho Chi Minh City, Vietnam.
4 : Univ Sheffield, Dept Geog, Sheffield S10 2TN, S Yorkshire, England.
5 : Shimane Univ, Estuary Res Ctr, Matsue, Shimane 6908504, Japan.
6 : Aix Marseille Univ, CNRS, Coll France, IRD,INRA,CEREGE, Aix En Provence, France.
7 : CNRS, USR LEEISA, Cayenne, French Guiana, France.
Source Scientific Reports (2045-2322) (Nature Publishing Group), 2020-05 , Vol. 10 , N. 1 , P. 8085 (7p.)
DOI 10.1038/s41598-020-64630-z
WOS© Times Cited 39

Since the 1990s the Mekong River delta has suffered a large decline in sediment supply causing coastal erosion, following catchment disturbance through hydropower dam construction and sand extraction. However, our new geological reconstruction of 2500-years of delta shoreline changes show that serious coastal erosion actually started much earlier. Data shows the sandy coast bounding river mouths accreted consistently at a rate of +2 to +4 km(2)/year. In contrast, we identified a variable accretion rate of the muddy deltaic protrusion at Camau; it was<+1 km(2)/year before 1400 years ago but increased drastically around 600 years ago, forming the entire Camau Peninsula. This high level of mud supply had sharply declined by the early 20th century after a vast canal network was built on the delta. Since then the Peninsula has been eroding, promoted by the conjunction of mud sequestration in the delta plain driven by expansion of rice cultivation, and hysteresis of long-term muddy sedimentation that left the protrusion exposed to wave erosion. Natural mitigation would require substantial increases in sediment supply well above the pre-1990s levels.

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