Citation by V. De Graff
“Prediction of spatially explicit rainfall intensity-duration thresholds for post-fire debris-flow generation in the western United States” exemplifies a published paper of distinction that advances knowledge concerning principles or practice of engineering geology. In fact, the content of this paper represents an advance of both principles and practice. The seminal work carried out by Dr. Susan Cannon defining empirical rainfall intensity-duration thresholds for post-fire debris-flow generation is acknowledged by the paper’s authors. Their paper describes a method for direct calculation of rainfall intensity-duration thresholds which avoids the lengthy process of developing empirically derived regional rainfall-intensity thresholds. Consequently, post-fire debris-flow hazard can be more readily determined in areas outside where empirically derived regional thresholds exist. The authors provide a cogent explanation of their methodology and a careful examination of how their rainfall intensity-duration thresholds compare to the existing regionally derived ones. The spatially explicit rainfall intensity-duration thresholds result in predictions of debris flow occurrence with an accuracy that can equal and, even, outperform regionally derived thresholds. Because the spatially explicit rainfall intensity-duration thresholds are compatible with existing approaches for post-fire debris-flow hazard assessment, the methodology facilitates operational expansion of hazard assessment and early warning into areas where empirically defined regional rainfall intensity-duration thresholds do not currently exist. Federal and State agency geologists charged with conducting post-fire debris-flow risk analyses are better served by this improved approach for determining the rainfall intensity-duration threshold. This enhanced capability is important throughout the western United States as the number and size of wildfires continue to increase and pose a greater threat to populated areas. Improved post-fire debris-flow hazard assessment contributes to effective siting of mitigation measures and facilitates the timely warning of triggering storms critical to protecting human life.
We are honored to be the recipients of the 2019 E.B. Burwell Jr. Memorial Award from the Environmental and Engineering Geology Division of the Geological Society of America for our paper “Prediction of spatially explicit rainfall intensity-duration thresholds for post-fire debris -flow generation in the western United States,” published in the journal Geomorphology in 2017.
The close temporal correlation between rainfall intensity and debris-flow occurrence has resulted in the operational usage of rainfall intensity-duration (ID) thresholds for debris-flow early warning in and below recently burned areas throughout the western United States. Our paper provides a statistics-based approach for estimating the rainfall intensities that may trigger post-fire debris flows in locations where historical data on debris-flow occurrence is limited or non-existent. Our research incrementally advances upon the seminal work of Dr. Susan Cannon and Dr. Joseph Gartner by synthesizing the traditional empirical approach for threshold definition with statistical models of debris-flow likelihood and magnitude.
It is gratifying that our work has been embraced by weather forecasters, post-fire response teams, and emergency managers and responders as a small part of their efforts for reducing public exposure to debris-flow hazards. However, we recognize that there is much more work that needs to be done towards improving our understanding and predictive accuracy of post-fire debris-flow initiation and propagation, as well as quantifying the evolution of debris-flow hazard as watersheds recover in the years following fire. We embrace these challenges and look forward to contributing to the continued advancement of post-fire debris-flow science and prediction.