Debris & Channel Obstruction Influences

Debris directly influences channel stability and pattern, profile and dimension evolution. Debris blockages include:

• None
• Infrequent
• Moderate
• Extensive
• Dominating
• Beaver Dams - Few
• Beaver Dams - Frequent
• Beaver Dams - Abandoned
• Human Influences

Flood forecasting can use information about blockages and debris to anticipate FGM and flood response. Rosgen reports that a reduction in woody debris, for example, in a headwater A, B, or G channel often results in increased Erosion and loss of the step/pool spacing, often at 4 to 5 Bankfull Widths in 2% slope channels or 1.5 to 2 Bankfull Widths in 6% slope channels.

Image courtesy of FISRWG