General bed degradation refers to a gradual lowering of the channel bed over a long stream reach. Bed degradation may occur naturally due to geologic factors, but is usually related to some type of human activity. Bed degradation often occurs below dams that trap significant portions of the sediment load. The stream erodes the bed in order to replenish its load of sediment. Bed degradation also often occurs upstream of stream reaches that are straightened, enlarged, or cleared and snagged because these types of alteration steepen the water surface and thus the erosive force of the flow upstream. Symptoms of bed degradation include exposure of previously buried bridge pilings, tree roots, geologic strata, etc. Toe erosion with upper bank failure and erosion by overbank runoff are often associated with bed degradation. The effects of general bed degradation are quite similar to the effects of headcutting. It is important to note that bank stabilization is generally ineffective if bed degradation is ongoing. Photograph (courtesy of USDA-ARS National Sedimentation Laboratory) shows bank erosion along Missouri River downstream from Fort Peck Dam in Montana, where about 2 m of general bed degradation has occurred since dam closure.