Debris flows and mudflows are dangerous. They destroy property, block roads, impact critical infrastructure like water and sewer lines and can be deadly. It is difficult to identify where debris flows and mudflows are likely to happen using existing mapping methods. Professionals need a more effective way to map debris and mudflow risk areas.
Communities and regional organizations currently lack methods to develop debris flow and mudflow risk data. They need this information to protect lives and property, especially in areas recently impacted by heavy rainfall or wildfire.
Areas recovering from wildfires can be extremely vulnerable to debris and mudflows. In 2021, one person was killed, and multiple properties were damaged by debris flows in the Columbia River Gorge in Oregon, in an area that experienced a wildfire in 2017.
The State of Oregon Department of Geology and Mineral Industries (DOGAMI) published Special Paper 53 . The goal of the paper was to give communities an effective method to identify their landslide risks from debris flows and associated mudflows.
The State of Oregon is using the new method developed by DOGAMI for FEMA-funded projects to map landslide risk. They are creating debris flow and mudflow hazard maps for areas recently impacted by wildfires in Oregon. These maps are giving communities and regional groups the information they need to help reduce risk to residents, infrastructure, and property after wildfires.
The approach DOGAMI developed is detailed in Special Paper 53, available on the DOGAMI website. The approach generates debris flow and associated mudflow hazard data that can be used for landslide risk awareness, local and regional hazard planning efforts, and emergency response.
It creates an objective and repeatable identification method for hazard areas. Knowing what areas are high-risk can help save lives and protect communities.
The science for this method has grown over the last 10 years. This new approach built on previous attempts and breakthroughs in debris flow research, modern Geographic Information Systems (GIS) technology and high-resolution lidar imagery which were each important for the creation of this method.
DOGAMI also learned it is essential to involve communities in the process as early as possible. The first project areas for this mapping method were selected by the state after hearing of the need for debris flow and mudflow hazard maps from communities in areas drastically impacted by wildfires in 2017 and 2020.
- Channelized debris flow susceptibility mapping protocol: Special Paper (SP) 53, 2022
- Landslide inventory mapping protocol: SP-42, 2009
- Shallow landslide susceptibility mapping protocol: SP-45, 2012
- Deep landslide susceptibility mapping protocol: SP-48, 2016
- Story Maps: Debris Flow Story Map, Landslide Inventory Story Map