Assessment of Changes in Channel Morphology and Bed Elevation in Mad River, California, 1971-2000

Book excerpt: The U.S. Army Corps of Engineers currently regulates gravel-mining activities in Humboldt County, CA, under the authority described in Sec. 404 of the Clean Water Act. In order to better understand the effects gravel mining has had on the Mad River, the U.S. Army Engineer District, San Francisco, initiated this study to examine changes in channel morphology and bed elevation between 1971 and 2000. This study focused on existing cross section data and historic aerial photography from a variety of sources, and river sediment (bed-load and bed-material) data collected by the USGS. It also used new cross-section data collected in 2000 and gravel extraction records. This information was used to quantify geomorphic changes in the river, to establish a sediment budget, and to determine a sustainable yield for gravel extraction based on maintaining the river in an equilibrium condition.