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Restoring the river discontinuum: looking at the example of beaver dams

1024 681 Stroud Water Research Center

Burchsted, D., M.D. Daniels, and R.M. Thorson. 2010. Pages 1797–1806 in R.N. Palmer (editor). Proceedings of the World Environmental and Water Resources Congress 2010, Providence, Rhode Island.

doi: 10.1061/41114(371)188

Abstract

River restoration targets are often set according to the River Continuum Concept, in which headwaters are narrow, forested, have coarse substrate, free-flowing water and sediment transport, and connect along a gradient from headwaters to mouth. This investigatory study examines this concept by comparing geometry and substrate of beaver-impounded with non-beaver (NB) headwaters at sixteen river segments in northeastern Connecticut. The beaver-impounded segments were classified in the following categories: valley-wide impoundments (VWI), in-channel dam series (IDS), and downstream of beaver dams (DD). The following width to depth ratios show distinct channels compared with NB: normal IDS (10.8±1.3 vs. 32.9±19.1), bankfull DD (10.2±1.5 vs. 20.0±6.2), and bankfull VWI (52.2±30.2 vs. 20.0±6.2). Additionally, bed substrate distinctions include the following: VWI (100% organic and fines vs. 0%), and IDS and DD (50% and 44% finer than coarse gravel vs. 0%). Given beaver dominance of pre-colonial U.S. river systems, these conditions should be incorporated into restoration targets.

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