Crevasse Splay

A crevasse splay is a sedimentary fluvial deposit that forms when a stream breaches its natural or artificial levee and deposits sediment onto the floodplain in a pattern similar to an alluvial fan. As floodwater spreads across the plain and loses energy, sediment falls out of suspension in graded layers; the breach can in some cases cause the river to abandon its old channel entirely, a process called avulsion, and deposits most often form on the outer banks of meanders where the water carries the most energy. Larger crevasse splay deposits can reach six meters thick at the levee and spread two kilometers wide, while smaller ones may be barely a centimeter thick.