Scientists found that changes in the behaviour of cyclones mean less sediment is running into rivers upstream of the Mekong delta, starving it of the sediments needed to guard against flooding.
The findings are significant in terms of Mekong delta sustainability into the future. The sediment load is already declining as a result of upstream damming and other human impacts such as sand mining. Climate models predict that tropical cyclones will get stronger as the climate warms but storm tracks will also move further to the North-East and away from the Mekong’s catchment, exacerbating the problems of a reduced sediment supply.
The research has global implications as other major rivers such as the Ganges (India/Bangladesh), Yangtze (China) and Mississippi (USA) have catchments that are regularly struck by tropical storms.
Some 500 million people live and work in the world’s major river deltas. This study indicates that changes in storm climatology, even in the river catchments far upstream of the deltas themselves, must also be considered when evaluating their future vulnerability to sea-level rise.