Geomorphic Stability of Sandbar 43.1L on the Colorado River in the Grand Canyon in Response to Ground Water Seepage during Fluctuating Flow Releases from Glen Canyon Dam

摘要

An investigation of sandbar erosion caused by ground water seepage was conducted by the National Park Service (NPS) in support of the Glen Canyon Environmental Studies (GCES) program. The investigation focused on evaluating the effects of shallow water seepage on the erosion of sandbars along the Colorado River in this area. Ground water movement is the result of recharge and discharge (seepage) from the river banks during daily river stage fluctuations. Erosion and deposition processes occur daily in response to changing hydrologic and hydraulic conditions. Seepage erosion occurs as water flowing down the sandbar to the river's edge concentrates and forms rills, scouring loose sand from the sandbar in the process. Sandbar aggradation could be caused by soil creep or sand deposition by near-shore eddy action.