Restoring Geomorphic Stability and Biodiversity in Streams of the Catskill Mountains, New York, USA

摘要

Many stream and river channels in North America have been straightened, widened, and hardened to stabilize channel banks and beds, but these efforts have typically given little or no consideration to biological integrity of the affected ecosystems. Application of natural-channel design (NCD) techniques and Rosgen's river classification system to mimic stable "reference-reach" morphology has helped reestablish natural stream-habitat conditions in more recent restoration projects. Stable channel morphology was restored using NCD techniques in a degraded reach in each of three Catskill Mountain streams during 2000 or 2001, in an attempt to decrease bed and bank erosion rates, reduce sediment loading, and improve water quality. Channel-restoration designs were based primarily on bank-full characteristics of nearby stable (reference) reaches and models of local stream hydrology and geometry. The effects of NCD restoration on biological integrity were assessed through before-after-control-impact (BACI) and analysis of variance (ANOVA) analyses of the changes in fish-community characteristics at treatment reaches relative to changes at unaltered control reaches after reach restoration. In general, relative species richness, total biomass, and biomass equitability increased significantly after treatment reaches were restored. The observed responses indicate that fish communities were affected by the restorations and by normal year-to-year variations in uncontrolled factors such as temperature, precipitation, and stream discharge. These findings indicate that biodiversity of fish communities in degraded Catskill Mountain streams generally benefit from use of NCD techniques to restore geomorphic stability.