OTREC-RR-11-19

Streambeds provide for the necessary habitats and spawning cycles of a healthy fish population. Oregon law requires underwater hydraulic structures to provide proper fish passage. Increasingly stringent regulations apply to fish passageways, and designers must consider a range of flows to accommodate fish movement and avoid structural failure. Fish passages, culverts or bridges, are built where roads cross streambeds. “Roughened channels” technique re-creates streambeds with the hydraulics necessary for adequate fish passage. This report examines long-term success factors for implementation of fish passageways, especially in the construction phase, and examines whether failures are due to inadequate range and mix of material gradation; unexpected water velocity; or inadequate mixing or compaction of materials during construction. Other factors may include the relationship of downstream slope to structure slope, well-graded fine soil materials in channel fill, and frequent site visits.