Exposed soil after forest fire, NPS photo, S. TreatEroding river bank, NPS photo, R. WasemBull trout, USFWS photo

The presence of fine sediments in streams is an entirely natural phenomenon caused by the erosive power of flowing water as it scours streambeds, rocks, and banks. Most streams maintain a dynamic balance between particle size and the amount of sediment transported and the flow rate and the slope of the stream. However, excessive input of fine sediment is thought to be the most common form of pollution affecting streams in the United States.

Within the Crown of the Continent, numerous human activities can lead to an increase in high rates of sedimentation: agriculture, forestry, mining, and urban development are just a few. Graveled and unimproved roads in rural areas and on public lands, also lead to increased sedimentation. High-severity wildland fires, particularly on steeper slopes, can temporarily cause increased water runoff and soil erosion during or following heavy precipitation events. All of these activities lead to increased sedimentation on streambeds which can upset normal stream dynamics and impact water quality and aquatic habitats for fish and invertebrates.