Evaluating and Prioritizing Stream Restoration in Mined Appalachian Watersheds.

摘要

The state of West Virginia requires stream mitigation to offset anthropogenic impacts to streams; consequently there is a high concentration of mitigation projects in the mountaintop mining/valley fill region. Projects are typically outside mine boundaries and sites are selected at the discretion of the West Virginia Department of Environmental Protection. This dissertation evaluated current in-stream, natural channel design (NCD) structures and prioritized future project locations. First, we assessed the Little Coal River, which is one of the largest physical restoration projects in the state. The Little Coal drains 994 km2 with extensive historic and contemporary coal mining. The objectives of our study were to quantify the effects of in-stream structure construction on stream channel morphology, fish habitat quality, sediment composition, bank stability, fish, and macroinvertebrate assemblages and to determine the extent to which benefits persisted over our study period (5 years). Our results indicate that the beneficial effects of structures include: improved fish habitat quality, increased bed complexity, and increased substrate diversity. Post-construction fish habitat quality and streambed complexity, although dynamic, appear to be relatively stable over time. We observed significant localized macroinvertebrate response to restoration that was mediated by shifts from sand dominated substrates to cobble and gravel. However, overall improvements to invertebrate assemblages at the river reach scale were not observed, because restoration did not affect substrate composition at the larger scale. In contrast, we did observe reach-scale effects of restoration on fish assemblages. However, the overall response was difficult to interpret as being ecologically beneficial or not. Total fish biomass, total abundance, and sucker abundance increased in response to NCD structure construction. Fish species richness and integrity measures remained unchanged, and gamefish abundance decreased on the Little Coal River. Second, we expanded our region and assessed the biological and physical responses to 14 restoration projects in an intensively mined region. Our results suggest that typical restoration practices consistently improve physical habitat quality regardless of drainage area. Restored reaches generally have higher habitat condition scores than adjacent reference reaches and tend to be higher than the average reach in the region. In contrast, macroinvertebrate assemblages demonstrated no measurable positive response to physical habitat restoration, regardless of drainage area, water quality, or the condition of neighboring streams. Fish assemblage response to restoration was strongly context dependent. Restoration projects on smaller streams (i.e. < 50 km2 drainage area) with lower electrical conductivity (< 1000 mus/cm) tended to result in a more positive response by fishes than projects on small, highly conductive streams. However, the most consistent response by fishes to restoration was an increased abundance and biomass of tolerant taxa.