Beaver dams and overbank floods influence groundwater–surface water interactions of a Rocky Mountain riparian area

Abstract

[1] Overbank flooding is recognized by hydrologists as a key process that drives hydrogeomorphic and ecological dynamics in mountain valleys. Beaver create dams that some ecologists have assumed may also drive riparian hydrologic processes, but empirical evidence is lacking. We examined the influence of two in-channel beaver dams and a 10 year flood event on surface inundation, groundwater levels, and flow patterns in a broad alluvial valley during the summers of 2002-2005. We studied a 1.5 km reach of the fourth-order Colorado River in Rocky Mountain National Park (RMNP), Colorado, USA. The beaver dams and ponds greatly enhanced the depth, extent, and duration of inundation associated with floods; they also elevate the water table during both high and low flows. Unlike previous studies we found the main effects of beaver on hydrologic processes occurred downstream of the dam rather than being confined to the near-pond area. Beaver dams on the Colorado River caused river water to move around them as surface runoff and groundwater seepage during both high-and low-flow periods. The beaver dams attenuated the expected water table decline in the drier summer months for 9 and 12 ha of the 58 ha study area. Thus we provide empirical evidence that beaver can influence hydrologic processes during the peak flow and low-flow periods on some streams, suggesting that beaver can create and maintain hydrologic regimes suitable for the formation and persistence of wetlands.

Hyporheic Flows Along a Channelled Peatland: Influence of Beaver Dams

“…Many of these valley bottoms may be wetlands simply because beaver may be maintaining riparian water tables near or at the ground surface by creating larger-scale (valley sized) hyporheic flow paths. Such hydrological connectivity may persist throughout wet and dry periods as this study and others (e.g., Westbrook et al, 2006) have shown that beaver keep hydrological conditions relatively static.…”

“…Depth to water in wells and piezometers was measured as per Westbrook et al (2006). Stream stage was measured along the outside casing of the A-series piezometers.…”

Mechanisms of carbon storage in mountainous headwater rivers

“…Beaver dams similarly enhance overbank flow, floodplain deposition and organic matter retention, and maintain high water tables that support dense stands of willow (Salix spp.) and other riparian shrubs [30][31][32] . The unequal distribution throughout the river network of carbon stored in floodplain sediment and coarse wood suggests that resource management designed to facilitate carbon storage can be most effectively focused on the relatively small proportion of channel segments with unconfined valleys.…”

Stratigraphic and Paleoenvironmental Reconstruction of a Mid-Pliocene Fossil Site in the High Arctic (Ellesmere Island, Nunavut): Evidence of an Ancient Peatland with Beaver Activity + Online Appendix Figures S1 and S2 (See Article Tools)

“…Peatlands are commonly initiated before beavers enter the system (Gorham et al, 2007); however, beaver activity can create water-level changes conducive to wetland formation (Westbrook et al, 2006). Once a peatland is established, beavers dig canals and help to create and maintain deep, open water by damming seepage (Westbrook et al, 2013).…”