Cataloging and synthesizing existing methods for the design of roadway-stream crossings for fish passage began in January 2005 with an extensive literature review covering the topics of culvert design and assessment to facilitate fish passage. A survey was posted online to gather input from design professionals across the country, and a Culvert Summit Meeting was held in Denver Colorado from February 15-16, 2006, to allow presentation and discussion of state-of-practice design and assessment techniques. Following the Summit meeting, a Technical Advisory Committee was developed with individuals specifically knowledgeable in the topics of interest. Members were crucial in shaping and reviewing the direction of these guidelines.

This document places current culvert design techniques into four categories based on design premise and objectives. These categories include: No Impedance techniques, which span the entire stream channel and floodplain; Geomorphic Simulation techniques, which create fish passage by matching natural channel conditions within the culvert crossing; Hydraulic Simulation techniques, which attempt to closely resemble hydraulic diversity found in the natural channels through the use of natural and oversized substrate; and Hydraulic Design techniques, which may utilize roughness elements such as baffles and weirs to meet species specific fish passage criteria during periods of fish movement.

Preliminary chapters covering the topics of fish biology and capabilities, culverts as barriers, fish passage hydrology, and design considerations aid in the selection of appropriate design techniques based on hydraulic, biologic, and geomorphic considerations. A further section presents examples of design techniques fitting the defined design categories. Design examples and case histories for a selection of design techniques are presented next, and are followed by a discussion on construction, maintenance, monitoring, and future research needs.