Water Resources Collections and Archives

In mountainous terrain, road-crossings may impair creeks by impeding fish passage, increasing sediment delivery to stream channels, and altering surface and subsurface flow paths. The objectives of this study were to quantify the short-term impacts of 6 road-crossing reconstruction projects on alluvial creeks in the Klamath National Forest of California. I used a Before-After-Control-Impact study design with 1 set of data pre-construction, 1 set of data immediately following construction, and 2 sets of data over the following 2 yr. The data included measures of fine-sediment deposition, grain-size, longitudinal-profiles, cross-sections, and benthic macroinvertebrates. This study found little impact on fine-sediment deposition or grainsize. The majority of longitudinal-profiles and cross-sections tended to incise upstream in response to culvert replacement, but the responses were largely site-specific. Furthermore, most morphological changes in slope and bed elevation were minimal. Most of the commonly used biological metrics did not show significant changes, but I observed significant changes (P = 0.005) in the populations of 3 orders of insects (Ephemeroptera, Plecoptera and Trichoptera) that are often used as indicators of disturbance and are a primary salmonid food source. This study upholds Best Management Practices as an effective technique for salmonid habitat restoration.