Recent flooding this fall highlights the need to understand the dynamics and power of rivers and streams. There are about 200 major river systems in Washington state and more than 260 bridge structures that cross these bodies of water. This is in addition to approximately 2,000 fish barrier crossings and 50,000 drainage culverts statewide.
|The Elwah River bridge on US 101 near Port Angeles, showing river erosion of one of the piers|
That's why when we set out to update our state Hydraulics Manual, we enlisted the help of hydraulic engineers from across the state, federal agency representatives and subject matter experts. The manual is used by state and local engineers, consultants and private developers. It provides step-by-step design guidance and standards for water crossings and stream restoration, especially in fish bearing waters. The manual also incorporates two-dimensional hydraulic modeling – a tool used to communicate the complex interactions between a river and transportation elements – that helps us develop solutions for river erosion around bridge foundations, known as “bridge scour.”
|2D modeling of the Elwah River bridge helped engineers develop emergency repairs of bridge scour.|
This collaborative work – a yearlong process that started in 2017 – was sponsored by the Washington State Transportation Innovation Council or STIC for short. STIC brings public and private transportation interests together to evaluate innovative solutions and help spread that knowledge so that we are using the best science and technologies available.
|Fish barrier corrections can be complex. This shows the old SR 202 Little Bear Creek culvert inside|
the new streambed and the pipe that carried the stream water during construction.
In early October, the American Association of State Transportation Officials and Federal Highway Administration recognized the collaborative work on our Hydraulics Manual with a STIC Excellence Award. Not only will the updated manual benefit engineers across our state, but it will also share our best practices with engineers across the nation.