Evaluating the impacts of urbanization and stormwater management practices on stream response

In this study, protocols were developed to standardize data generation for identifying mechanistic linkages between urbanization and stream response to identify stormwater management practices that minimize negative ecological impacts in urban streams. These protocols were applied in the North Carolina Piedmont. Eight watersheds spanning a gradient of urbanization were used to identify linkages between indicators of aquatic ecosystem health and hydrologic and geomorphic metrics derived from a 20-year continuous stream flow record. The 20-year continuous stream flow records were generated using EPA Storm Water Management (SWMM5) models calibrated to 18 months of measured flow data.;The T_0.5 hydrologic metric was affected by both land use and channel geometry changes. Modification of rural channel cross-sections to geometries observed in urban watersheds of similar size significantly changed T_0.5 hydrologic metric values highlighting the importance of controlling channel erosion. When stormwater controls were applied in a watershed and channel geometry was left in its original, undeveloped, state, changes in the values of the T _0.5 hydrologic metrics were minimized. Long-term changes in erosion potential were minimized when stormwater controls were applied.;Biotic response was related to both hydrologic and geomorphic metric values, indicating that restoration of hydrology may not allow for the attainment of biotic goals if habitat is not also restored. In urbanizing situations, preservation of natural hydrology and restrictions on increases in erosion potential can reduce geomorphic changes, although changes in upland sediment supply also must be accounted for. These relationships were shown for the North Carolina Piedmont, but are also applicable throughout the United States.;Ephemeroptera, Plecoptera, and Trichoptera (APT) richness and a benthic index of biotic integrity (B-IBI) for the eight North Carolina Piedmont watersheds were found to be linearly related to T_0.5, T₁, and T₂ hydrologic metrics, which describe the percent of time discharge is above the peak discharge of an n-year return interval storm. Macroinvertebrate metrics were shown to be logarithmically related to predominant substrate size. Overall, predominant grain size was better predictor of macroinvertebrate metrics than cumulative excess shear stress.