Benjamin Hayes, Program Director Watershed Sciences & Engineering Bucknell University.
Landscape Memory: The Legacy of Logging on Pennsylvania Streams and Implications for Adaptive Approaches
Traditional stream restoration efforts throughout the midAtlantic and northeastern United States have limited success because their fluvial systems remain in a disequilibrium condition after a century of widespread logging. By the mid-1800s sediment delivery to streams was greatly increased and channels were dredged, straightened, and cleared of trees and large boulders to facilitate log drives. Hydraulic geometries were altered as splash dams, berms, cribbing, and sluices were built. Aquatic habitat was further degraded by channel widening, loss of water depth and velocity variations, and deposition of large bars downstream of artificial constrictions and other areas of energy loss. These watersheds remain in a protracted phase of fluvial adjustment, with episodic movement of legacy sediments during large floods, resulting in widespread aggradation, chute cut-offs, floodplain sedimentation, and channel avulsion. Damage to roads, bridges, and infrastructure can be catastrophic. We have been experimenting with adaptive restoration approaches involving removing legacy barriers (berms, roads, and splash dams) and adding large woody debris to the channel to increase overall channel complexity and promote floodplain connectivity and ecosystem function over a range of discharges. As a result, groundwater storage and hyporheic exchange is increased, with sustained habitat in marginal channels and floodplain depressions. Hydraulic energy is more uniformly distributed throughout the fluvial system, promoting sediment and carbon sequestration, greater pool depth and availability of spawning gravels, and healthier native brook trout populations.
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Hosted by: Environment and Natural Resources Institute, College of Agricultural Sciences