Transportation agencies frequently need to manage stream crossings that were located and built without regard for broader scale physical and biological processes. In these situations, sustainable solutions to maintenance burdens and habitat damage frequently necessitate involvement with co-managers and stakeholders.
In Washington State, the Department of Transportation is restoring fish passage to hundreds of culverts. At the same time, there is an increasing maintenance burden, particularly with those crossings that were not designed to sustainably accommodate hydrologic or geomorphic processes. For some fish passage barriers, the best option is to re-route a stream to mimic its historic patterns. This typically involves off-right-of-way work, and stakeholders.
WSDOT has embarked on several stream re-alignments in this way. We have found that in some areas, stakeholders realize co-benefits of fish passage restoration. The Mud Creek project is a great example of this. King County had purchased land and property at perpetual risk of flooding. The flooding was due primarily to the stream being confined to a tiny fraction of its original alluvial fan, and due to the undersized culvert.
Working with the county and other stakeholders, WSDOT has created a project that restores a portion of the alluvial fan, creates significant amounts of riparian habitat, and takes advantage of County land purchased to reduce flood damage. We will be eliminating the annual dredging that was needed at the stream crossing, and at the same time lengthening the stream and creating a large riparian buffer, and greatly reducing risk of flood damage.
In Skagit County, another fish passage project has exemplified the need for working with stakeholders. Childs Creek is a steep mountain stream that enters the gentle floodplain of the Skagit River, and state route 20 crosses the stream at the critical transition zone. The existing culvert is slated for fish passage barrier correction, but to build a more sustainable crossing – including being passable into the future - restoration of alluvial fan processes was recognized as a necessity. Furthermore, like Mud Creek, the county has embarked acquisition of property that is frequently flooded, downstream of the highway. The current design includes a re-alignment of the stream outside of its current highly constricted route, and restoration of a portion of its pre-development fan. This provides space for sedimentation, and greatly expands the riparian habitat.
WSDOT has found that not only can there be co-benefits to stakeholders, but involvement of stakeholders can help WSDOT achieve its goals. It is essential to coordinate with stakeholders, not only as good neighbors, but also to take advantage of shared goals and resources.