DESIGN FOR FISH PASSAGE AT ROADWAY STREAM CROSSINGS: SYNTHESIS REPORT

A waterway of perceptible extent that periodically or
continuously contains moving water. It has definite bed and banks, which serve
to confine the water and includes stream channels, secondary channels, and
braided channels. It is often determined by the “ordinary high water mark” which
means that line on the shore established by the fluctuations of water and
indicated by physical characteristics such as clear, natural line impressed on the
bank, shelving, changes in the character of soil, destruction of terrestrial
vegetation, the presence of litter and debris, or other appropriate means that
consider the characteristics of the surrounding areas.

This document is a design reference for the classification, assessment, design or
retrofit of a roadway-stream crossing to facilitate fish passage. It is the result of
a comprehensive literature review completed to categorize design procedures,
case histories, and culvert assessment techniques. No new recommendations
for a universal design procedure are made; rather, a compilation of design
options used in different geographic regions is included to allow the user to select
the most appropriate design method for their unique situation. A collection of
design examples and case histories is intended to add clarity to the design
methodology selection.
In order to provide stream reach connectivity for all wildlife, removal of road
barriers or the installation of a bridge spanning the floodplain are ideal; however,
this report presumes that a narrower, fish-friendly, installation is both permitted
and desirable for economical or logistical reasons. It is recognized that fish are
not the only animals requiring habitat connectivity for long-term population
viability, and future versions of this circular are intended to cover aquatic
organism passage (AOP) in more detail. This report is intended solely as a
reference for the design, retrofit, or replacement of a road stream crossing to
meet fish passage requirements.
The scope of this report is also limited to culvert installations. If the total culvert
span including all barrels and fill between barrels exceeds 6.1 m (20 ft), it is
called a bridge according to the Federal Highway Administration code
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