What Are Debris Flows
A debris flow is a natural phenomenon where a mixture of mud, sand, gravel, rock and water rushes down a slope due to gravity.
The movement of a debris flow can be divided into three steps: initiation, transit and deposition. In the initial step, a slope collapses causing debris to begin to move downhill, usually down a curved ravine covered with sparse vegetation. Next, as the debris flow continues downhill, it erodes the bank of the ravine into U-shape, mostly taking place in valleys or downstream. Finally, the debris flow is deposited at the mouths of gullies and forms debris fans, which are tongue-shaped with large boulders deposited on the surface or on the edge of the fans.