This course focuses on culverts; the design team should recognize that an appropriate structure for any given crossing may be a bridge. This course is not intended to conflict with or replace accepted guidance and procedures adopted in particular locations. When specific water crossing design methods are required in the jurisdiction where the crossing is located, those methods should be applied. In addition, local and regional requirements may overlay additional steps on this design approach.

Since fish have been the primary focus of acquatic organism passage (AOP) design efforts over the years, and much has been learned about fish specifically, many of the references to AOP in this course derive directly from what is known about fish. However, the broader scope of AOP is the focus of the course.

Because of the variety of fish and other aquatic species in the U.S., the complex nature of fish behavior and the variation in such behaviors and capabilities over the various life-stages, designing hydraulic structures with satisfactory AOP characteristics remains a challenging endeavor. Over the years, resource agencies and others have assembled a large amount of empirical data and field experience to guide the design of roadway structures, particularly culverts, for passage. Much of the resulting criteria are based upon the natural geomorphic characteristics of streams supporting the aquatic ecosystems of interest, and many of the procedures implementing those criteria seek to replicate the stream and floodplain characteristics and geometries within the roadway crossing structure. The “stream simulation” approach, as developed by the United States Forest Service (FSSWG, 2008), is one approach that is state of the art. This course material is based on FHWA Publication Number FHWA-HIF-11-008: Culvert Design for Aquatic Organism Passage.

At the conclusion of this course, the learner will have a better understanding about Designing Culverts to Facilitate Aquatic Organism Passage as well as an understanding of the following topics:

• Methodology and design procedure applicability
• Culverts as passage barriers
• Culvert assessment and inventory
• Fish biology and passage hydrology
• Stream geomorphology
• Design procedure and construction
• QA and QC procedures of construction