Vegetation Impacts Upon Stream Width

Hydraulic geometry relationships are often used in the hydraulic design of channels for stream restoration projects. Hydraulic geometry theory is based on the concept that a river system tends to develop in a predictable way, producing an approximate equilibrium between the channel and the inflowing water and sediment (Leopold and Maddock 1953). The theory typically relates a dependent variable, such as width or slope, to an independent or driving variable, such as discharge or drainage area. Hydraulic geometry relationships are developed from field observations at stable and alluvial cross-section for a specific river, watershed, or for streams with similar physiographic characteristics. However, the relationships are empirical, and extrapolation to watersheds, or to times different from those represented by the data used to develop a given relationship, is risky. As design tools, hydraulic geometry relationships may be useful for preliminary or trial selection of channel width.