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.