Colorado Gulch Restoration:
Enhancing Habitat. Enhancing Experience.
BY REVERSING DECADES OF CHANNELIZATION, WE WERE ABLE TO OFFER MORE HABITAT FOR FISH AND ACCESS FOR HUMANS. NOW WE CAN GET BACK TO ENJOYING THE BIG WOOD RIVER IN PEACE.
PROBLEMS AND LIMITING FACTORS AND HISTORY
The 2017 water year for the Big Wood River was above normal. The snow water equivalent (SWE) for the basin on April 1st, 2017 above the U.S. Geological Survey (USGS) stream gauge at Bullion Bridge (#13139510) in Hailey, Idaho was at 178% of normal. This led to a 50 year flood event for the Big Wood River which compromised the structural integrity of the Colorado Gulch Bridge. The previous road bridge length was too short to allow proper river function and connectivity to the floodplain; which led to the road bridge’s infrastructure to be compromised and unsafe for travel during the high flow event of 2017. In the last 20 years the road bridge’s infrastructure was compromised three times due to its short length and restricting the river to the main channel and not allowing connectivity to the floodplain . The bridge was deemed unsafe for travel in early spring of 2017 and removed on January 5th, 2018. What remains is the bridge abutments, rip rap along the banks, and the bridge approach fill material. Because of this, the area around Colorado Gulch has been channelized, and disconnected from legacy side channels and floodplain habitat.
PROJECT GOALS & BENEFITS
The Colorado Gulch (COG) river restoration project was a unique opportunity to enhance floodplain habitat and reconnect historic side channels approximately 1,200 feet of length by removing approximately 1,300 cubic yards (cy) of rip-rap and artificial fill that historically protected the COG road and bridge. The main limiting factor for salmonid habitat on the Big Wood River (BWR) is disconnection of its floodplain to allow the river to create complex habitat and access critical rearing areas during high flow events. Disconnection has occurred due to development of homes and other infrastructure that reduced the BWR from an anastomosing channel form to a single channel form for the majority of the river. Disconnection of historic side channels have reduced rearing and spawning habitat which has led to decreased survival and productivity of salmonid populations in the BWR. Removal of the rip-rap allowed us to construct large woody debris structures to enhance complex salmonid habitat, and provide cover by enhancing riparian habitat.
A non motorized bridge will be constructed in the fall of 2025 to open access to Colorado Gulch on the west side of the river. This project is a great example of how we can reverse decades of bad practices such as channelization, bank hardening, and disconnecting habitats through infrastructure, and enhance salmonid habitat and recreational access.
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