Culverts are the Culprits!
Access to all habitat types at all life stages is important for maintaining healthy salmon populations. CRWP and partners have developed a tool to prioritize culvert replacement projects and continue efforts to improve fish passage throughout the watershed.
For salmonids, access to healthy spawning and rearing habitats are important for maintaining high fish productivity. Certain species of salmonids can spend 2-4 years in freshwater using a variety of habitat types before smolting and migrating to the ocean. Resident species such as grayling can be very nomadic as well. Therefore, unimpeded movement through culverts is critical at all life stages to allow access to all habitat types. Poorly designed, installed, maintained and/or failed culverts can impede fish passage and limit connectivity of habitat.
Prioritizing Fish Passage Improvement Projects
The CRWP and partners recognize the importance of access to spawning and rearing habitats, but culvert replacement projects are very expensive and the ecological benefits can vary greatly from one stream to the next.
To help prioritize how to spend limited fish habitat restoration funds, CRWP has developed a protocol that assigns numerical values to culvert conditions (constriction, perch, velocity) and ecological conditions (i.e. fish presence/absence and quantity/quality of fish habitat) associated with road crossings.
This scoring system generates a number score for each culvert and provides an objective ranking of potential fish passage improvement projects. This information helps partners identify the potential projects that have the most ecological benefit to the aquatic system and make the most of limited resources. This data has been integrated into an online mapping tool to provide a visual tool for interpreting the prioritization data and assisting with planning efforts.
We use this culvert prioritization protocol as a planning tool and for facilitating discussions with permitting agencies, property owners and land managers, and the Alaska Department of Transportation & Public Facilities.
For more information about scoring methodology and how to interpret scores, download our Culvert Prioritization document here.
Successful Culvert Replacement Projects
The following are examples of culvert removal and habitat enhancement projects that the CRWP and partners have completed in recent years.
Eccles Creek & Whiskey Creek
In the 1980s, the Eccles Creek Bridge was replaced with a culvert. From the waterline, the culvert was perched 6” and acted as a velocity barrier for rearing juveniles. ADF&G and USFWS agreed replacement would improve fish passage.
Whiskey Creek culvert was under flood capacity for five-year peak flows,created a velocity barrier for juvenile fish passage and resulted in flooding to local neighbors. Storm water runoff was a visible problem to many locals.
Replaced Eccles & Whiskey Creek culvert and worked with community partners interested in stream routing to improve drainage and reduce sediment runoff.
Improved access to quality habitat for coho, pinks, and cutthroat trout.
Power Creek Road, by old Ketchum air site
Three small culverts were constricting the water flow from the upstream side of Power Creek Road and impacting the downstream gravel spawning beds.
Replaced three culverts with one arch pipe to allow for the stream to travel under the road in a more natural condition.
Improved spawning habitat for sockeye salmon and access to spawning habitat for pink salmon.