TOWARDS AN INTEGRATED FRAMEWORK FOR RIVER RESTORATION IN NEW ENGLAND (Invited Presentation)

Because of the long history of land use change (e.g. logging, reforestation, residential and road network development) and industrialization (e.g. dams), river systems across New England have been profoundly altered. New England has the highest density of dams in the U.S. and the greatest frequency of road crossings, resulting in major discontinuities in key physical processes and population/habitat fragmentation for diadromous and resident fishes. The history of these diverse stresses makes it difficult to base river restoration on a coherent set of ‘reference’ conditions. To capture the impacts of habitat fragmentation, we first outline a conceptual framework delineating the characteristic anthropogenic alterations, recovery trajectories, and management options in New England rivers from their headwaters to their mouths focusing on the frequency and location of dams, dam removal, and culverts. Explicitly including the interaction between anthropogenic disturbance and environmental context longitudinally may help to identify appropriate restoration strategies and to determine the relative efficacy of restoration efforts in specific parts of the river network. To show the geomorphic responses to these anthropogenic impacts we present results on the geomorphic and sedimentological impacts of dams and dam removal in tributaries of the Connecticut River. Results indicate the general uniformity of physical response when considering the covariant changes in channel geometry and sediment transport. However, while the covariate response may be predictable, the changes in any particular metric remain uncertain: e.g. progressive adjustments occur in width in the West River of VT following 5 decades of impoundment, while channel slope adjustments predominate in the Ashuelot River, NH following dam removal. This indeterminate singular response limits river restoration as ecological ‘recovery’ may depend more on specific responses not simply covariate geomorphic adjustments.