2.1 Site Description
This study was conducted within a river-floodplain system along the North St. Vrain River, Colorado (Figure 1). The river drains an 84km2 watershed within Rocky Mountain National Park and has a snowmelt driven hydrograph with late spring/early summer snowmelt peak flows and summer streamflow recession (Figure 1). The river has a multi-thread planform within the river-floodplain system which is 1.5km long, 200m to 300m wide with an area of 0.47km2. The floodplain has high spatial heterogeneity with a mosaic of beaver ponds, side channels and wetlands (Laurel & Wohl, 2019). Beaver colonies are active within the reach and geomorphic structures in the floodplain are strongly impacted by historic and current beaver activities including dam construction, channel dredging and pond creation. The floodplain is vegetated with riparian species including willows (Salix spp.), river birch (Betula spp.), and quaking aspens (Populus tremuloides ).
Eleven surface water sites were established within the river-floodplain system (Figure 1b). There were four sites along the river including at the upstream (Inflow) and downstream (Outflow) boundaries of the river-floodplain reach and along two major channel braids within the river-floodplain system (Main-Mid & Main-Braid, see Figure 1). To capture the heterogeneity of aquatic habitats across the floodplain, we included four side channel sites (Side-01 to Side-04), two connected pond sites that had an upstream surface connection to the river (Pond-Con-01 & Pond-Con-02) and one isolated pond (Pond-Iso) with no apparent surface channel connection to the river.