Footstep-induced sediment displacement in the Grand Canyon

Abstract

The Glen Canyon Dam has severely altered the riparian zone of the Colorado River in the Grand Canyon. One result of the controlled river discharge is more efficient prediction of water stages at the major rapids, leading to higher visitor use. Increased visitation results in heavy foot traffic, trampling along the river banks, erosion of the campsite soils, and the destruction of vegetation. Erosion occurs when the surfaces are roughened, exposing them to wind transport and runoff. In addition, each footstep physically displaces sand downhill. The results of a field experiment designed to measure the amount of sand displaced by footsteps show that each year trampling alone displaces 230 m3 of sand downslope and into the river. With the controlled river flow, no natural processes exist to replace the lost sediment.