Sediment-Trapping by Beaver Ponds in Streams of the Mid-Atlantic Piedmont and Coastal Plain, USA

Abstract

The effect of beaver ponds on sediment deposition is undocumented in the Piedmont and Coastal Plain of Virginia and North Carolina. We used 3 methods to exam- ine sedimentation: 1) depth-integrated base-flow sampling, 2) repeat channel-surveys, and 3) sediment-accumulation pads. During base flow, Piedmont ponds exported sedi- ment and Coastal Plain ponds had little or no effect on downstream suspended-sediment concentration. Most ponds accumulated sediment within the channel until dam breaching. Ponds inundating the floodplain trapped more sediment. Ponds of varying configura- tion trapped sediment differently. Mean floodplain accretion rates in these beaver ponds (2002-2003: 20 mm/yr 2003-2005: 15 mm/yr) greatly exceeded the mean deposition rate of similar unimpounded streams in these areas. Intact Piedmont ponds trapped 11 m 3 /yr on the floodplain and 77 m 3 /yr in the channel. Intact Coastal Plain ponds trapped 107 m 3 /yr on the floodplain and 8 m 3 /yr in the channel.