Geology

Protection Against Erosion

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Science  04 Feb 2005:
Vol. 307, Issue 5710, pp. 646
DOI: 10.1126/science.307.5710.646d

River and stream erosion rates and the resulting river profiles are becoming more widely recognized as depending on a complicated and incompletely documented suite of factors. For instance, some streams and rivers appear to be eroding their bedrock at the geologically extreme and unsustainable rates of several centimeters per year; hence, other processes must be contributing to bedrock dynamics. Over a 7-year period, Stock et al. monitored several rivers in Taiwan and in the Pacific Northwest of the United States. These rapidly eroding rivers had all been historically scoured of sediment. This history and the authors' measurements imply that long-term stream erosion, at least in areas with weak bedrock, is influenced more by the ability of rivers to entrain a thin covering of sediment, which reduces wear, than specific bedrock properties. In areas of high slope, debris flows, which periodically scour streams and rivers and thus allow rapid downcutting, may be the most critical factor. — BH

Geol. Soc. Am. Bull. 117, 174 (2005).

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