3.1. 2020 Field Study
Our results demonstrate the wash habitat feature is more physically diverse than any other river segment along the lower SRR with wash and boundary habitat reaches containing 17% more unique geomorphic units (e.g., pools, riffles, backwaters) on average than reference reaches, with 70% of primary wash habitat comprised of diverse habitat. We found that boundary habitat was the most complex, containing a combined greater diversity of geomorphic units and substrate composition when compared to sampled reference and valley plug reaches (Figure 2). Our reference sites contained >800 m2 of riffle habitat and only a very small area (<7 m2) of large woody debris (Figure 2A). Reaches within the valley plug itself were composed of only a small area of pool habitat (16 m2). In contrast, the boundaries of the valley plug contained >123 m2 of pool habitat, 149 m2 of riffle habitat, >34 m2 of large woody debris and a very small section (4 m2) of backwater habitat. On average, boundary habitat contained >1,100% more pool habitat than the other reaches. Based on the results of pebble counts, we found that boundary sites contained a mixture of silt and sand substrate, with 64% of substrate comprised of silt. In comparison, reference sites were more complex than anticipated, containing >54% silt substrate, >33% sand, >4% gravel and 7% boulder. Valley plug reaches were comprised entirely of silt (Figure 2B).