Integrated watershed hazard assessment for wildfire, floods, and debris flows in the Navajo Nation

More frequent and extreme events in the southwestern United States, including wildfires and intense storms, raise concerns about forest and watershed health. High-severity crown fires are growing more extensive and the summer monsoon storms that can extinguish wildfires also create flood and debris-flow hazards. These events have lasting social and ecological impacts, and responding to them is challenging because of the rapid fire-to-flood transition time. Pre-wildfire planning is essential for mitigation of hazardous impacts to forested watersheds, and the homes, communities, and infrastructure within and far downstream of a burned area.

Along with Ann Youberg (Arizona Geological Survey/University of Arizona), I am conducting an integrated watershed hazard assessment to evaluate and map the probability and potential impacts of extreme fire-flood-debris-flow events in watersheds of the Navajo Nation.

https://chguiterman.github.io/Navajo_Watersheds/map.html

This project brings together resource managers from the Navajo Nation Division of Natural Resources, Division of Transportation, Department of Emergency Management, and BIA Wildland Fire Management. Managers are directing our attention to those watersheds that they perceive most at-risk.

The risk assessment will consist of computer simulations of fire, flooding, and debris flows that are calibrated and corroborated with local ground-based data. Simulations will be run for (1) current forest conditions pre-fire, (2) current forest conditions post-fire, and (3) treated forest conditions post-fire. Simulated forest health treatments will include thinning and prescribed burning for reduction of tree density and forest fuels, and will aid in targeting specific areas for greatest resource benefit by restoration activities in the near future.

Results from this study will be used in planning within the Navajo Nation Integrated Resource Management Plan (IRMP) and the Navajo Nation Climate Adaptation Plan, as well as on-the-ground efforts for greater resilience, including infrastructure improvements and pre-disaster hazard mitigation projects.

We are currently funded by the BIA Tribal Resilience Program through 2020.