The impact of beaver dams on the morphology of a river in the eastern United States with implications for river restoration

Abstract

Restoration projects in the United States typically have among the stated goals those of increasing channel stability and sediment storage within the reach. Increased interest in ecologically based restoration techniques has led to the consideration of introducing beavers to degraded channels with the hope that the construction of beaver dams will aggrade the channel. Most research on beaver dam modification to channels has focused on the long‐term effects of beavers on the landscape with data primarily from rivers in the western United States. This study illustrated that a role exists for beavers in the restoration of fine‐grained, low gradient channels. A channel on the Atlantic Coastal Plain was analyzed before, during, and after beaver dams were constructed to evaluate the lasting impact of the beaver on channel morphology. The channel was actively evolving in a former reservoir area upstream of a dam break. Colonization by the beaver focused the flow into the channel, allowed for deposition along the channel banks, and reduced the channel width such that when the beaver dams were destroyed in a flood, there was no channel migration and net sediment storage in the reach had increased. However, the majority of the deposition occurred at the channel banks, narrowing the channel width, while the channel incised between sequential beaver dams. The study indicated that where channels are unstable laterally and bank erosion is a concern, the introduction of beavers can be a useful restoration tool. However, because of the likelihood of increased channel bed erosion in a reach with multiple beaver dams, they may not be the best solution where aggradation of an incised channel bed is the desired result. Copyright © 2014 John Wiley & Sons, Ltd.

Sediment and nutrient storage in a beaver engineered wetland

“…Levine and Meyer (2014) reported large sediment losses but the remnants of the dam structure were found to trap sediment, which was rapidly colonised by plants and stabilised. In contrast, other studies have observed rapid loss of pond sediments following dam collapse (Curran and Cannatelli, 2014;Levine and Meyer, 2014). It is likely that, as with the site studied, where closely-spaced, multi-dam complexes exist, these will provide a major buffering effect, reducing the likelihood of dam failure and, in so doing, also reducing the downstream release of sediment from any single dam failure.…”

Wood and sediment storage and dynamics in river corridors

“…The effects of beaver dams on in‐channel entrainment thresholds and transport rates are similar to those described for other forms of LW. Beaver dams decrease sediment entrainment and transport within the backwater zone upstream from the dam (Butler and Malanson, ; John and Klein, ; De Visscher et al , ), enhance bed scour where flow plunges over a dam (Pollock et al , ), enhance spatial variation in average bed grain size (Curran and Cannatelli, ), and can create substantial pulses of sediment transport when a dam fails (Butler and Malanson, ; Russell et al , ).…”

Impacts of beaver dams on channel hydraulics and substrate characteristics in a mountain stream

“…Previous research has shown the ability of beaver dams to have a significant impact on each of these areas. As a result, many restoration projects are beginning to use beaver and beaver dam structures as an ecological and cost‐effective approach in restoration and management (Andersen & Shafroth, ; Burchsted et al , ; Curran & Cannatelli, ; DeBano & Heede, ; DeVries et al , ; Pollock et al , ).…”