Beaver dam analogue configurations influence stream and riparian water table dynamics of a degraded spring‐fed creek in the Canadian Rockies

Abstract

Beaver dam analogues (BDAs) are intended to simulate natural beaver dam ecohydrological functions including modifying stream hydrology and enhancing stream‐riparian hydrological connectivity. River restoration practitioners are proactively deploying BDAs in thousands of degraded streams. How various BDAs or their configurations impact stream hydrology and the riparian water table remains poorly understood. We investigated three types of BDA configurations (single, double and triple) in a spring‐fed Canadian Rocky Mountain stream over three study seasons (April–October; 2017–2019). All three BDA configurations significantly elevated the upstream stage. The deepest pools occurred upstream of the triple‐configuration BDAs (0.46 m) and the shallowest pools occurred upstream of the single‐configuration (0.36 m). Further, the single‐BDA configuration lowered stream stage and flow peaks below it but raised low flows. The double‐BDA configuration modulated flow peaks but had little influence on low flows. Unexpectedly, higher flow peaks and low flows were recorded below the triple‐BDA configuration, owing to groundwater seep. Similar to the natural beaver dam function, we observed an immediate water table rise in the riparian area after installation of the BDAs. The water table rise was greatest 2 m from the stream (0.14 m) and diminished with increasing lateral distance from the stream. Also noted was a reversal in the direction of flow between the stream and riparian area after BDA installation. Future research should further explore the dynamics of stream‐riparian hydrological connections under various BDA configurations and spacings, with the goal of identifying best practices for simulating the ecohydrological functions of natural beaver dams.

Rediscovering, Reevaluating, and Restoring Lost River-Wetland Corridors

“…Restoration explicitly designed to restore river-wetland corridors is gradually starting to occur, as exemplified by wetmeadow restoration in Europe (Grootjans and Verbeek, 2002;Klimkowska et al, 2007) and the United States (Booth et al, 2009;Riggins et al, 2009;Hartranft et al, 2011;Silverman et al, 2019;Voosen, 2020), "stage 0" restoration projects in the United States Pacific Northwest (Powers et al, 2019), and beaver reintroduction and mimicry efforts throughout the United States (Pollock et al, 2014;Bouwes et al, 2016;, Canada (Muni and Westbrook, 2021), Europe (e.g., Nolet and Rosell, 1998;Fustec et al, 2001), and across the United Kingdom (Puttock et al, 2015). To be successful, restoration requires a sound understanding of past and present conditions and trajectories, informed by analyses of historical records and key biogeomorphic processes across a range of spatial and temporal scales (e.g., Woelfle-Erskine et al, 2012;Rathburn et al, 2013;Brierley and Fryirs, 2016).…”

Influence of beaver mimicry restoration on habitat availability for fishes, including Arctic grayling (Thymallus arcticus)

“…Although we cannot evaluate passage explicitly with our dataset, use of the BMS reach by salmonids was minimal, suggesting that increased salmonid survival and production observed in other systems may be site‐ or structure‐type specific (Bouwes et al., 2016). The BMS reach had riffles and pools that were narrower and a pool:riffle ratio that was higher than in a prior study documenting the factors positively associated with high densities of Arctic grayling (Liknes & Gould, 1987), suggesting availability, type or spacing of riffle habitat needs further evaluation (Munir & Westbrook, 2021). Habitat complexity achieved by other types of small dam structures, such a willow weave dams, may be fundamentally different from that achieved by constructed riffles, and these differences may be further compounded by differences in underlying geology or historical land use (Bouwes et al., 2016).…”

“…The immediate habitat around BMS may be more relevant to less mobile species such as invertebrates and periphyton because they cannot as easily or quickly move to avoid undesirable locations. Future work might consider the number, spacing and type of structure to determine how BMS will alter lower trophic levels (Munir & Westbrook, 2021) and ultimately influence food availability for fish (Reinert et al., 2022).…”

Estimating widespread beaver dam loss: Habitat decline and surface storage loss at a regional scale

“…As enthusiasm for beaver-related restoration increases, opportunities for restoration and management lie between the two steady states occasional beaver dam capacity is predicted or where beaver dam capacity has been significantly decreased from historic estimates, streams are likely to have shifted or started to shift to a drier steady state. Therefore, vegetation restoration or beaver mimicry structures could be deployed to shift streams to a more suitable state prior to beaver reintroduction (e.g., Munir & Westbrook, 2021;Scamardo & Wohl, 2020) (Figure 6).…”