Oregon’s Fish Passage Design Flows: Maximum and Minimum
Low Design Flow Minimum
- Depth is Primary Concern
- “95% Exceedence flow for migration period of the fish species of concern” (ODFW Guidelines)
- Also use the 2 Year – 7 Day Low Flow
High Design Flow Maximum
- Velocity is primary concern
- “the flow that is not to be exceeded more than 10% of the time during the months of adult migration” (ODFW Guidelines)
- Approximation methods offered in ODFW guidelines for small streams are overly conservative, they give something more like a 1% exceedence flow.