Colorado Gulch
Enhance Habitat. Enhance Experiences
By reversing decades of channelization, we can offer more habitat for fish and access for humans. So we can get back to enjoying the Big Wood River in peace.
Project Overview
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 CGB 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 offers a unique opportunity to enhance floodplain habitat and reconnect historic side channels, approximately 1,200 feet in length, by removing around 1,300 cubic yards 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 the disconnection of its floodplain, which prevents the river from creating complex habitats and accessing critical rearing areas during high-flow events. This disconnection has occurred due to the development of homes and other infrastructure, which has reduced the BWR from an anastomosing channel form to a single channel form for the majority of the river. The loss of historic side channels has decreased rearing and spawning habitats, leading to reduced survival and productivity of salmonid populations in the BWR.
Removing the rip-rap will also allow for the construction of large woody debris structures to enhance complex salmonid habitat and provide cover by improving riparian habitat. Several pedestrian bridges will be constructed to open access to Colorado Gulch and the riparian floodplain.
This project is a great example of how we can reverse decades of harmful practices, such as channelization and bank hardening, to enhance salmonid habitat and improve recreational access.
Before and After Aerial Images: Restoration Impact
Before
After