New guide makes designing environmentally friendly culverts easier and more efficient

culvert

Minnesota transportation practitioners now have access to a comprehensive culvert design guide to help preserve stream connectivity and promote the safe passage of fish and other aquatic organisms through culverts.

“Minnesota’s 140,000 miles of road and 92,000 miles of streams and rivers meet at tens of thousands of places,” says Matt Hernick, an associate engineer with the U of M’s St. Anthony Falls Laboratory. “Because of the variety of ecological regions in the state, the range of culvert geometries, and other factors, no single solution can work for culverts statewide. The new guide fills this information void.”

Culverts are a cost-effective solution to allow traffic to cross over smaller waterways, but they have historically been designed with only flood flows and the safe passage of vehicles in mind—and not the health of streams and the organisms that depend on them, says Hernick, the project’s principal investigator. Professor John Nieber of the Department of Bioproducts and Biosystems Engineering was the co-investigator.  

The researchers used results from previous MnDOT studies and consultations with experts to develop the culvert design guide. They worked with experts from the Minnesota Department of Natural Resources (DNR), the U.S. Forest Service, and others with knowledge of civil engineering, aquatic organism passage, and stream geomorphology to determine the scope of the guide. 

They also sought information for the guide from a wide range of resources including past research, documents from federal agencies, guidance from other states, permit requirements from the DNR, and databases of fish populations, stream attributes, and culverts. Additionally, researchers surveyed state and local highway transportation practitioners to identify current design practices and their degree of effectiveness.

The 221-page guide—amply illustrated with photos, charts, and more—is available to users online. Sections include site assessment, analysis and tools, best practices, the current regulatory context, and a design method selection chart. Benefits for users may include more-efficient design and permitting processes and lower construction costs. 

“This design guide offers a practical, Minnesota-based perspective on how to design culverts that allow aquatic organism passage and preserve stream integrity and connectivity across the state’s diverse ecological regions,” says Nicole Bartelt of MnDOT’s Bridge Office. 

The project was sponsored by MnDOT and the Minnesota Local Road Research Board. Additional research is under way to assess how storm vulnerability and future hydrologic scenarios could affect culverts and fish passage.

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