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The success of fish migration through culverts is dependent on the swimming ability of the fish and the hydraulic conditions of the culvert. Properly designed and constructed culverts can minimize the impact on fish passage. Because culverts are typically more economical than bridges, it is appropriate to evaluate when to use culverts and to predict the effects of such culvert installations. During the consideration of alternatives for structures for fish passage, culverts should not be automatically eliminated. This publication has tried to examine the aspects of culvert design and operation relative to the existing information that has been published in previous studies. Ideally, a culvert installation should not change the conditions that existed prior to that installation. This means that the cross-sectional area should not be restricted by the culvert, the slope should not change, and the roughness coefficients should remain the same. Any change in these conditions will result in a velocity change which could alter the sediment transportation capacity of the stream. A truly successful culvert design would include matching the velocities of the fish's swimming zone in the culvert to the swimming capacity of the design fish. Unfortunately, not enough research has been completed to make this an acceptable criterion of culvert design. This approach is preferred because it is easier to reduce the velocities in the swimming zone by increasing the boundary roughness than it is to reduce the mean velocity of the entire culvert. This publication contains some relatively simple guidelines which can reduce the installation problems of culverts in streams containing migrating fish when combined with the expertise of an experience fish biologist, engineer, and hydrologist.
The Bureau of Land Management and the Forest Service manage more than 41 million acres of federal lands in Oregon and Washington, including 122,000 miles of roads that use culverts--pipes or arches that allow water to flow from one side of the road to the other. Many of the streams that pass through these culverts are essential habitat for fish and other aquatic species. More than 10,000 culverts exist on fish-bearing streams in Oregon and Washington, but the number that impede fish passage is unknown. Ongoing agency inventory and assessment efforts have identified nearly 2,600 barrier culverts, but agency officials estimate that more than twice that number may exist. Although the agencies recognize the importance of restoring fish passage, several factors inhibit their efforts. Most significantly, the agencies have not made enough money available to do all the necessary culvert work. In addition, the often lengthy process of obtaining federal and state environmental clearances and permits, as well as the short seasonal "window of opportunity" to do the work, affects the agencies' ability to restore fish passages quickly. Furthermore, the shortage of experienced engineering staff limits the number of projects that can be designed and completed. BLM and the Forest Service have completed 141 culvert projects to remove barriers and to open an estimated 171 miles of fish habitat from fiscal year 1998 through 2000. Neither agency, however, knows the extent to which culvert projects ultimately improve fish passage because they don't require systematic post-project monitoring to measure the outcomes of their efforts
This new edition of the best-selling book describes the main types of fishways and fish facilities used around the world to assist the passage of fish over dams and other obstructions to their migration. It also focuses on the protection of fish (mainly young fish) from the hazards encountered in their downstream migrations. The book brings together the type of knowledge and research needed to decide on the facility used as well as its design and operation. It emphasizes the need for both biologists and engineers to collaborate in the design and indicates in what fields such collaboration would benefit fisheries conservation in the future. This is the Second Edition of the only book to bring together all of these topics worldwide under one cover.