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Hydraulics Engineering


Fish Passage Summit

Summit Objectives | Attendees | Format | Background

Summit Objectives

The Fish Passage Summit Meeting brought together individuals with in-depth knowledge, experience, and an interest in identifying appropriate applications and limitations of state-of-practice and state-of-the-art methods for the design and retrofit of road-stream crossings to ensure fish passage. Current procedures for categorization of barriers were discussed, followed by design procedures for culvert and bridge applications, and design and retrofit case histories.

The objectives of the summit were to:

  • Provide a forum for open discussion/communication on the state-of-the-art techniques available for the design and retrofit of road-stream crossings; including the conditions under which they were developed, and their applicability.
  • Discuss the applicability and reliability of stream surveying techniques used to determine the fish passability of existing structures; including methods of prioritization and categorization.
  • Gather input from fish passage professionals on any other pertinent issues surrounding fish passable structures.


Design professionals interested or experienced in the design, retrofit or analysis of road-stream crossings requiring fish passage. This includes a wide range of individuals including researchers, technology practitioners, university researchers, consultants, state DOT personnel, state resource agency personnel, or anyone else with relevant input or experience.


  • Presentations by invited speakers covering the topics of fish passage assessment, retrofit, and design of fish crossings and a few select case histories of fish crossing installations and monitoring followed by brief question and answer sessions.
  • An open discussion period about state-of-the-art and state-of-practice fish crossing design and retrofit, fish crossing analysis, and culvert case histories.


Waterway crossings such as bridges and culverts play a critical role in our nation's transportation network. Properly designed, constructed, and maintained, bridges and culverts provide safe passage across all sizes of streams and rivers, estuaries, bays, reservoirs, and lakes. Waterway crossings represent a key and expensive element in our overall transportation system. While ubiquitous in urban areas, there are thousands of bridges and culverts that also service untold miles of remote roads in our forests, national parks, and other environmentally sensitive areas.

Bridges and culverts that do not span the entire channel and floodplain can impact the stream channel through a constricted bridge or culvert opening. The constricted reach changes the characteristics of water flow near and through the hydraulic structure, typically increasing water velocity while reducing water depth. Severe encroachments, most commonly found at culvert crossings, isolate the floodplains from the main channel and force even flood flows through the culvert barrel.

Secondary impacts on the riverine environment are common and include scour of the streambed through and downstream from the structure, and upstream progressing channel incision. As a result, many bridges and culverts act as stream barriers to juvenile and adult fish passage. Higher velocities may exceed fish swimming ability, and scour at culvert outlets may prove excessive for fish to leap into the structure. Often, high quality upstream fish habitat is isolated and disconnected from downstream river and stream corridors by structures that are simply impassable for native fish.

There is currently no generalized approach for design of fish passage for bridges and culverts that brings together current practice, policy, and research results. Federal Highways is collaborating with Washington State University to create Hydraulic Engineering Circular - 26 "Design for Fish Passage at Bridges and Culverts." This manual will be a design reference for anyone interested in classifying, designing or retrofitting a road-stream crossing to ensure fish passability. A comprehensive literature review has been completed to categorize national and international design procedures, case histories and culvert assessment techniques. A compilation of design options endorsed in different geographic regions is intended to allow the user to select the most appropriate design method for their unique situation. A collection of case histories and design examples will be included to add clarity to the design methodology selection.

More Information


Bert Bergendahl

Updated: 04/07/2011

United States Department of Transportation - Federal Highway Administration