2.2.2. Site Characterization and Mapping
To contextualize baseline conditions for the SRR, as well as the relative impact of the Cottonwood Wash valley plug, we mapped valley bottom extents (Fryirs, Wheaton, & Brierly, 2015) to provide a basis for normalization. The valley is defined as the area between the adjacent hillslopes (Wheaton et al., 2015), and the valley bottom is the area that contains the active channel(s) and active floodplain and could plausibly flood in the contemporary flow regime (Wheaton, Bennett, Bouwes, Maestas, & Shahverdian, 2019). We used multiple lines of evidence to delineate the valley bottom margins for the study reaches including satellite imagery, Digital Elevation Models (DEMs) and field observations of the surrounding landscape. We assumed the valley bottom extents are constant in order to establish a consistent basis for normalization (Bartelt, 2021). Next, we interpolated a valley bottom center line and used this to characterize valley bottom or site length. We calculated integrated valley bottom width for target sites by dividing valley bottom area by site length. For each data capture event, we digitized features representing tier 1 and tier 2 geomorphic units, as well as inundation extent and type (described in greater detail below; Wheaton et al., 2015).
We also conducted a slope analysis for the valley plug and each of the reference reaches. The following equation was used to calculate the slope of the valley centerline
\begin{equation} m=\frac{\text{rise}}{\text{run}}=\frac{y_{1}\ \ y_{2}}{x_{1}\ \ x_{2}}\nonumber \\ \end{equation}
where y1 is the elevation at x1, which is the upstream end of the valley centerline, and y2 is the elevation at x2, which is the downstream end of the valley centerline.