This web page was developed as an informational resource for people involved in planning, designing and constructing stream crossings on small streams less than 20 feet wide.
For a brief preview of a culvert replacement project, click here to view the 18 Mile Creek Culvert Replacement Video (7:13 seconds 23 mb)

 

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Building a fish-friendly stream crossing requires an understanding of not only fishery biology but also basic engineering and construction principles as well as fluvial geomorphology (that is the processes that form and maintain stream habitat).

Our intent in developing this web site was to provide the tools needed to plan and construct a fish passage structure that will be efficient, safe and conducive to fish passage.

The procedures we suggest were derived from best practices recommended by public and private agencies and were selected to provide practical guidelines for designing long lasting, stable road crossings that will have minimum adverse affect on fish and their stream habitats.

A number of state, federal and municipal agencies may have jurisdiction and permit authority over construction activities on streams and wetlands. Any person involved with planning, designing and constructing a stream crossing improvement should consult with the appropriate federal, state and local agencies from a very early stage within the planning process and comply with permit and construction regulations.

Through this web page, we hope you will learn about:

• How to identify problem fish passage structures.

• How to evaluate a site for possible fish passage remediation.

• How to design and install replacement fish passage structures that are friendly to fish and their habitats.

• Where to find additional resources for planning, designing and construction of fish friendly stream crossings.

Background:

Early in our history, rivers ran wild, and fish followed them according
to their needs. This was a time when our fishery resources
seemed abundant and without end.

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Since then, millions of culverts, dikes, stream diversions, dams, and other artificial barriers were constructed for transportation, to impound and redirect water for irrigation, flood control, electricity and drinking water. Many of these alterations have changed the open access features of rivers and streams and have taken their toll on our fishery resources. Improperly designed or damaged stream crossings are by far the most common cause of these problems.

~  Restoring fish passage benefits people, fish and the environment  ~

The vast majority of crossings are culverts or bridges on small streams. Nearly all culvert installations are intended to serve the purpose of providing vehicle access, however, many also have an unintended function- they can block the migration of fish up or down streams.

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They also alter the geomorphic processes by which river channels form and maintain habit over time. For example, they may block or constrict the passage of sediment and large wood being transported by the river, and prevent channel migration.

Fish movements within streams are vital for maintaining healthy populations. Spawning migrations like those made by trout and salmon may be the most visible and dramatic, but seasonal (or even daily) movements upstream or downstream to find food supplies, refuge from predators, preferred temperatures or cover may also be critical.

Where fish habitats are divided into small segments (fragmented) by man-made barriers, whole populations may be eliminated, reduced or genetically damaged through the effects of isolation and inbreeding. The consequences can be disastrous for fish populations and other aquatic organisms within a watershed. It is a fundamental fact, fish need to move. For example, many fish need to move between feeding and spawning areas and make other seasonal movements to important habitats.

  Click here to download this presentation (1.5 mb).