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Use of Multi-Functional In-Channel Structures in Catskill Mountain Streams

Jillian Cole
Stantec Consulting
Albany, NY

Stantec has been working with local Stream Management Programs (SMPs) in the Catskill Mountain region to improve long-term channel stability and sediment transport within local stream systems, in an effort to reduce turbidity and sediment contributions to downstream reservoirs, and to improve stream habitat for trout and other aquatic organisms. Bank erosion, especially occurring as large-scale hillslope failures, continues to drive restoration prioritizations in the region, ultimately protecting New York City’s drinking water sources.

Currently, Stantec and the SMPs have designed and implemented four projects throughout the region to mitigate active bank erosion on large failing banks. These projects are generally located in high-energy streams with narrow floodplains, steep valley walls, and a high bed load supply consisting primarily of cobble and gravel. Roadway alignments, existing infrastructure, and presence of bedrock outcroppings are all factors that constrain restoration approaches and project reach lengths. To overcome these obstacles, Stantec combined selective channel realignment with targeted in-channel structures and treatments, which include incorporation of large woody debris, native stone, and boulders designed to withstand the high velocities of the system. Treatments were also designed to be resilient during large flooding events while acting as analogues for naturally occurring stream features. Completed projects have been monitored during and after significant storm events to evaluate the function of installed treatments, and overall project success has been high. This presentation will discuss the design and construction of these treatments, including modifications from lessons learned, and how they have performed over time in high-energy systems.