How Do Streams and Rivers Respond to Surges of Sediment?
Writing in the August 2001 issue of the journal Water Resources Research, Mary Ann Madej, a research geologist at the USGS Western Ecological Research Center, reports on changes that steep mountain river channels undergo following disturbances such as wildfires, landslides, volcanic eruptions, mining and removal of dams. These disturbances can flush into streams large additions of sand and gravel as sediment pulses. Sediment pulses are of concern to land managers because they influence: the availability of aquatic habitat for salmon; sediment delivery to downstream reaches, water supplies and reservoirs; and the stability of infrastructure features such as bridge crossings and buried pipelines. Predicting how channels will react to these pulses is important in stream restoration work. Madej found that after sediment pulses occurred, the river channels were commonly shallower, less complex and rough, and had irregularly spaced gravel bars, pools and riffles. Over time the structure and
