New model could predict sudden shifts in river deltas

LONDON, May 20 (UPI) -- Researchers at Imperial College London are developing a new tool to predict avulsions, the sudden shift in the flow of water through a river delta.

As rivers slow down and begin to meander at the end of their journey from mountain to sea, they spread out, deposit the sediments they've carried and form deltas. While river deltas appear relatively tame, they are tremendously powerful.

A sudden shift in the path of a river through the delta can decimate entire communities.

"Avulsions are often thought of as the 'earthquakes' of deltas because of the damage they wreak," researcher Vamsi Ganti, an earth scientists at ICL, said in a news release.

"Sudden and unpredictable changes in the course of a river can rapidly flood neighboring land, meaning that people often have to abandon their communities before they are swallowed by the river system," Ganti explained. "Our research confirms the factors that make these avulsions occur, which could ultimately help people around the world make their communities more secure."

Ganti and a team of scientists from ICL and the California Institute of Technology built a model delta in the lab to study how changes in the river and delta can trigger an avulsion.

The model allowed researchers to simulate a variety of flood conditions and flood patterns, condensing geologic processes that normally take hundreds or thousands of years to play out. Their research confirmed the importance of flooding and lobes in dictating delta shape and movement.

Previously, researchers have noticed that each delta has a unique lobe length. The lobe is the leaf-like pattern made by a river's deposited sediment. Once the lobe reaches its uniform length, an avulsion occurs and a new lobe is created.

Testing in the lab proved that a constant pattern of flooding was key in encouraging the uniform lobe length, and that a delta's lobe length corresponded to the gradient and the depth of the river.

The researchers hope to tease out these relationships so they can predict future avulsions. They detailed their latest findings in the journal Science Advances.