Culvert Design for Fish Passage

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Culvert design is extremely important because fish passage in rivers, creeks and other waterways are essential for reproduction and survival of many fish species. If poor designs of culverts are installed, upstream fish migration can be impeded. Many culverts have been designed especially for fish migration and passage. Culverts have many impacts to stream system even when fish passage is successful including; channel disruption during construction, hydraulic effects up and downstream, increased or decreased flow rates or many other impacts. When stream crossings are necessary three possibilities are considered, a bridge, a culvert, or an environmentally conscious culvert. When considering fish migration, a bridge is most effective although for financial reasons rarely a feasible option. An environmentally conscious culvert is the only other option, which at a reasonable price will successfully allow fish migration and will have minimum disturbance to the stream.
Many different culvert options are available for stream crossings comprising of a no slope design, a hydraulic design, or a stream simulation design. When considering any one of these designs many concerns need to be addressed including; direct habitat loss, water quality, upstream and downstream channel impacts, ecological connectivity, construction impacts, and possible failure. Direct habitat loss can occur if the culvert is installed in current fish spawns, growth areas, feeding areas, or migration areas. Water quality is effected during construction of the culvert as dirt particles or other foreign material enters the stream. Upstream and downstream channels are affected if flow rates are changed by water depth or channel depth and can further effect stream qualitie...

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...gns are a few of the more acceptable options concerning this issue. Each option has many advantages and disadvantages although a bottomless steam simulation culvert can be considered to more effective for complete mitigation of all effects a roadway crossing has on a stream’s ecosystem. Baffles can be considered a fantastic option if conditions to not allow the development and construction of a new culvert system. Although baffles will not fully solve the problem it will allow sufficient migration of even weak fish species. There are a vast number of negative effects even a single roadway crossing can have on a stream, and it is the responsibility of all engineers and society to moderate its effect with greener solutions.

Works Cited

http://www.dot.ga.gov/doingbusiness/PoliciesManuals/roads/Drainage/G4-MAN9.pdf
http://wdfw.wa.gov/publications/00049/wdfw00049.pdf

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