Inventory of debris flows from 1995 to 2024 in thecascade range, oregonproject period: 06 01 2025 through 05 31 2026DEBRIS flows are one of the most devastating natural, and sometimes human…

The U.S. Geological Survey (USGS) Cooperative Landslide Hazard Mapping and Assessment Program (CFDA 15.821) awarded $201,794 to the Oregon Department of Geology and Mineral Industries (DOGAMI) on June 1, 2025, to create a comprehensive inventory of debris flows in the Cascade Range from 1995 to 2024. The project will utilize 30 years of statewide orthophotography and LiDAR (Light Detection and Ranging) topographic data to systematically identify and document debris flow occurrences across the region. This inventory will serve as critical calibration data for debris flow hazard modeling and will support Oregon's understanding of debris flow frequency and distribution patterns in an area where post-fire debris flows and volcanic hazards pose significant threats to people and infrastructure.

Deliverables from this 12-month project will include a spatial database of identified debris flows with temporal attribution, contributing to the scientific understanding of Oregon's debris flow hazard landscape and supporting future risk mitigation efforts. The inventory aligns with the program's priority of developing advanced geospatial mapping products and assessments that reduce landslide and debris flow losses. By documenting historical debris flow activity, DOGAMI will provide emergency managers, planners, and communities with essential data needed to understand susceptibility patterns and inform hazard mitigation strategies in debris flow-prone areas throughout the Cascade Range.

Inventory of debris flows from 1995 to 2024 in thecascade range, oregonproject period: 06 01 2025 through 05 31 2026DEBRIS flows are one of the most devastating natural, and sometimes human exacerbated disasters. Inoregon, debris flows pose significant threats to people and infrastructure. Debris flows are a unique landslidetype that can move rapidly and thus pose a life safety concern. As population growth continues to expand andas development in debris flow susceptible terrain increases, greater damage and losses are likely to result.most of oregons debris flow damage has been associated with atmospheric river type rainstorms and or rainon-snow events. The recent (2020) megafires in western oregon and particularly in the cascade range, areincreasing the already relatively high debris flow hazard. The eagle creek fire (2017) located in the cascaderange in the columbia river gorge has had 204 post-fire debris flows (burns and others, in press), one whichresulted in a fatality in 2021. Debris flow on volcanoes (located in the cascade range) are also potentialthreats to parts of oregon.debris flows in oregon tend to happen repeatedly in basins susceptible to the process, therefore inventoriesof past debris flows are critical to understanding future hazard. Burns and others (2022) published a methodto model future channelized debris flow hazard initiation, transport, inundation runout in oregon. The method by burns and others (2022) requires a debris flow inventory to calibrate the model. Weare very fortunate to have serial statewide orthophotos from 1995-2024 in oregon. These remote sensingdatasets were collected every several years for the past 30 years, so they have good spatial and temporalcoverage. The region the recipient is proposing to map also has complete lidar topographic data, which compliments the orthophotos. The recipient proposes to create an inventory of debris flows from the 1995 to 2024 orthophotos of the cascade range, oregon and include a report describing the mapping. The debris flow inventory will be created in a geodatabase and published with metadata as part of the grant deliverables. The recipient will hire one or two interns to help accomplish this proposed project. The recipient proposes to start the project in june 2025 and complete IT in one year. The mapping area includes a diverse landscape with many cities and counties. IT also includes all the east-westhighway corridors and infrastructure transmission in oregon. Partnering with federal agencies to complete debris flow hazard mapping on federal land is another priority in oregon. The recipient plans to share the new debris flow inventory mapping data with the cities, counties, state, and federal landowners and assist them in ways to use the new data to perform debris flow risk reduction, for example implementation of planning measures guided by preparing for landslide hazards, a land use guide for oregon communities. The data will also be used by dogami in future SP-53 hazard modeling. After the hazard modeling, risk analysis can be performed toidentify areas of high risk and continue risk reduction. The oregon department of forestry has expressedinterest in using the dataset to analyze post-fire salvage logging effects on debris flow initiation. This datasetcan also be used in the future to correlate past storms and debris flow rates. This type of historic data isfoundational when predicting future rates with climate change. The tasks accomplish the national strategy for landslide loss reduction risk reduction priority areas: P1.landslide hazard mapping and assessment and P3. Education and outreach. The tasks also accomplishprioritizations outlined in the national landslide preparedness act including ways to reduce landslide hazardsand risks to minimize loss of life and property.