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https://www.nationalacademies.org/trb/events

Updating Streamflow Statistics for Central and Eastern Oregon to Reduce Flooding Risk

Regional flood frequency equations are needed to plan, maintain, and protect critical infrastructure against flood risks across Oregon. When designing and maintaining hydraulic infrastructure in central and eastern Oregon, Oregon Department of Transportation (ODOT) professionals face persistent challenges of sparse streamflow data, highly variable precipitation, diverse geologic and topographic features, and irregularities due to large water withdrawals for agriculture. While reliable streamflow statistics can be obtained for western Oregon locations using the ODOT funded U.S. Geological Survey (USGS) StreamStats tool, the current accuracy of the underlying regression equations for locations in central and eastern Oregon are much less reliable, and in some cases not available. Further, though the StreamStats tool may be helpful for some central and eastern Oregon locations, these regression equations—now more than 20 years old—may not accurately reflect present-day conditions, particularly where basins have experienced significant shifts in long-term precipitation and temperature patterns, land use, or water withdrawals. Accurate streamflow statistics are essential for sizing bridges, culverts, and roadside drainage, ensuring infrastructure longevity through variable flow conditions and extreme weather events. The objective of this research is to update Oregon streamflow statistics and the heavily used StreamStats tool so that this tool can be relied upon for ODOT hydraulic design in central and eastern Oregon. This update process will employ new machine-learning and refined statistical approaches, together with more expansive data from states that share central and eastern Oregon’s hydraulic and hydrologic characteristics. Specifically, this research aims to: (1) enhance design accuracy, (2) support infrastructure longevity under future conditions, (3) optimize resource allocation, (4) improve planning and reduce maintenance, and (5) facilitate regulatory compliance and environmental stewardship with effective fish passage design and habitat protection.