A STREAM-GRADIENT INDEX APPLIED TO SUBHUMID MONTANE STREAMS |
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| Authors: | Jerome V DeGraff |
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| Institution: | USDA Forest Service , Richfield, Utah |
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| Abstract: | Hack (1973) introduced the stream-gradient index as a measure to analyze longitudinal stream profiles. It is derived from the channel slope at a point and channel length as measured along the longest stream above that point. In the eastern United States, empirical evidence shows the stream-gradient index to be a rough approximation of stream power or competence. Validity of this relationship in other geomorphic and climatic regions was unproven. Eight canyon drainages in the Bear River Range, north-central Utah, provide a basis for testing the validity of stream-gradient index analysis in a subhumid montane area. These drainages are found to have a drainage area to discharge function, rate of increase in channel width downstream, and coverging stream network with an average length proportional to a power of the drainage similar to Hack's original study area. These similarities indicate that use of stream-gradient indices as approximations of stream power are valid in subhumid montane areas. Stream-gradient index analysis of canyon streams in the Bear River Range illustrates drainage adjustment to tectonic activity, bedrock lithology, and structural attitude. |
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