Metrics for assessing the downstream effects of dams

We evaluate three metrics representing the drivers of channel change downstream from dams. A balance between changes in sediment supply and transport capacity identifies conditions of sediment deficit or surplus. A Shields number represents the competence of postdam flows and the potential for incis...

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Bibliographic Details
Published in:Water resources research 2008-04, Vol.44 (4), p.n/a
Main Authors: Schmidt, John C., Wilcock, Peter R.
Format: Article
Language:English
Subjects:
dams
fluvial
geomorphology
human impacts
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Summary:We evaluate three metrics representing the drivers of channel change downstream from dams. A balance between changes in sediment supply and transport capacity identifies conditions of sediment deficit or surplus. A Shields number represents the competence of postdam flows and the potential for incision under conditions of sediment deficit. A ratio of postdam to predam flood discharge provides a metric for the scale and rate of channel change, especially width. The metrics are calculated for more than 4000 km of some of the major rivers in the western United States. More than 60% of these rivers are in sediment deficit, and only a few reaches are in sediment surplus. The sediment balance can be used to assess the relative effort involved in reversing undesired conditions of deficit or surplus.
ISSN:0043-1397
1944-7973
DOI:10.1029/2006WR005092