Road Ecology Center

This paper presents a standard list of procedures for designing natural fish passage structures in urban streams. Before any design can commence, designers need to thoroughly investigate the target fish species and the hydrology of the study reach. Designs of riffle grade controls (RGCs) and flow constrictor/step pools (FC/SPs) start with topographic surveys, geomorphic assessments, and tailwater measurements. Results of the geomorphic assessment will determine which structure should be constructed: RGCs for sand/gravel bedded streams and FC/SPs for cobble/boulder bedded streams. Each structure type has a unique hydraulic modeling approach; however, stone sizing and channel bank stabilization procedures are standard. Construction management is of great importance because installing these structures is not routine and it is incumbent on the designer to ensure that the contractor complies with the spirit and the intent of the design.