Culvert Design
What is it?
Culverts are commonly used at stream road crossings to allow flow to pass beneath the road. However, many culverts were poorly designed and incorrectly installed and have altered stream hydrology and sediment flow, scoured downstream substrate, created streambed downcutting below the culvert, and have changed stream flow velocities preventing fish and aquatic organism migration. Culverts can be properly designed to accomodate stream crossing needs and minimize the impact to stream hydology, sediment flow, and aquatic animal migration. Non-functional stream crossings and culverts should be replaced to restore natural stream functions and allow for stream recovery.
Conservation Benefits
- Maintains connectivity for aquatic organism migration
- Maintains connectivity for gene flow between aquatic organism populations
- Prevents changes in stream hydology and sediment flow
- Protects access to breeding and swaning areas
What does it include?
Designing culverts includes many considerations like
- location in the watershed
- stream type and classification
- stream base flows and flood flows
- maintenance of stream depth, current velocity, and substrate
- maintain appropriate sediment transport
- inclusion of part of the floodplain
- fish and aquatic organism passage and migration needs
- wildlife passage and migration needs
- prevention of downstream scouring and drop in streambed elevation
- prevention of stream widening
Common culvert designs and shapes include round, elliptical, flat-bottomed, and box.
Culvert Design Links
- Cross drain culverts (p 40; Texas Forest Service and Texas Forestry Association)
- Culvert modification (p 171; Center for Watershed Protection)
- Culvert replacement and removal (p 175; Center for Watershed Protection)
- Culverts: guidlines for the selection and design of culvert installations (Office of Bridge Development Manual for Hydrologic and Hydrolic Design)
- Design of road culverts for fish passage (Washington Department of Fish and Wildlife)
- Ditch relief culvert (p 10; Midpeninsula Regional Open Space District)
- Culvert sizes for cross-drainage of roads (p 104; Virginia Department of Forestry)
- Open top pipe culvert (p 22; West Virginia Division of Forestry)
- Overcoming barriers to fish passage: fish passage through culverts (p 306; Cooperative Research Centre for Catchment Hydrology)
- Pipe culverts for cross drainage (p 20; West Virginia Division of Forestry)
- Pipe culverts for stream crossing (p 23; West Virginia Division of Forestry)
- Recommended specifications: cross road drainage culverts (Texas Forestry Service)
- Urban resource management: culverts (p 10-13; Nevada State Conservation Commission)
Culvert Design Bibliography
- Clevenger et al. 2001. Drainage culverts as habitat linkages and factors affecting passage by mammals. Journal of Applied Ecology 38: 1340-1349.
- Gibson et al. 2005. Loss of fish habitat as a consequence of inappropriately constructed stream crossings. Fisheries 30: 10-17.
- Taylor and Goldingay. 2003. Cutting the carnage: wildlife useage of road culverts in north-eastern New South Wales. Wildlife Research 30: 529-537.
- Wellman et al. 2000. Long-term impacts of bridge and culvert construction or replacement on fish communities and sediment characteristics of streams. Journal of Freshwater Ecology 15: 317-328.
- Wheeler et al. 2005. Impacts of new highways and subsequent landscape urbanization on stream habitat and biota. Reviews in Fisheries Science 13L 141-164.
- Whipple et al. 1981. Erosion potential of streams in urbanizing areas. Journal of the American Water Resources Association 17: 36-45.