Culvert design is extremely important because fish passage in rivers, streams and other waterways is essential to the reproduction and survival of many species of fish. If poorly designed culverts are installed, fish migration upstream may be hindered. Many culverts have been designed specifically for fish migration and passage. Culverts have many impacts on the river system, even when fish passage is successful, including: disruption of the channel during construction, upstream and downstream hydraulic effects, increased or decreased flows, or many other impacts. When watercourse crossings are necessary, three possibilities are considered: a bridge, a culvert or an environmentally friendly culvert. When it comes to fish migration, a bridge is most efficient, although for financial reasons this is rarely a feasible option. An environmentally friendly culvert is the only other option that, at a reasonable price, will successfully allow fish migration and minimal disruption to the stream. Many different culvert options are available for stream crossings, including a no-slope design, a hydraulic design, or a flow simulation design. When considering any of these designs, there are many concerns to consider including: direct loss of habitat, water quality, upstream and downstream channel impacts, ecological connectivity, impacts of construction and possible failure. Direct loss of habitat may occur if the culvert is installed in current fish spawning grounds, nursery areas, feeding areas, or migration areas. Water quality is affected during culvert construction when dirt particles or other foreign materials enter the watercourse. Upstream and downstream channels are affected if flows are changed based on water depth or channel depth and can further affect stream quality...... middle of paper. .....gns are some of the most acceptable options regarding this problem. . Each option has many advantages and disadvantages, although a bottomless steam simulation culvert may be considered more effective in completely mitigating all effects of a road crossing on a stream's ecosystem. Baffles can be considered a fantastic option if conditions do not permit the development and construction of a new culvert system. Although baffles will not completely solve the problem, they will allow sufficient migration of even weaker fish species. There are a large number of negative effects that even a single road crossing can have on a waterway, and it is the responsibility of all engineers and society to moderate these effects with greener solutions. doingbusiness/PoliciesManuals/roads/Drainage/G4-MAN9.pdfhttp://wdfw.wa.gov/publications/00049/wdfw00049.pdf