Human activity is causing most of the world’s river deltas to sink. The biggest impact is from dams and reservoirs trapping sediment that normally flows downstream, but other factors such as manmade channels and levees are causing problems also. Without the constant replenishment of sediment, the deltas are slowly sinking.
Of the world’s 33 major deltas, 24 are in trouble. About 85% of the deltas have experienced severe floods. As the ocean levels rise the problem will only get worse.
Since the combined delta area represents over 100,000 square miles, with over 500 million inhabitants, delta sinking and flooding will continue to be a growing problem.
Storm impact will increase along these low-lying deltas, and will get worse over time as the areas continue to sink. As delta areas sink they no longer act as buffers to major storms, allowing storm surges to hit with greater impact. In the United States, this effect was illustrated by Hurricane Katrina.
Photographs:
Top: Lena River Delta (Russia)
Bottom: Mississippi River Delta (United States)
