For postfire debris flows, the USGS performs hazard assessments using operational models to estimate the likelihood of debris-flow initiation and the magnitude of debris-flow volume. This opportunity is aimed at research to inform several emerging priorities related to postfire debris-flow hazards that will refine or result in new operational products.
Description of the Research Opportunity
The USGS Landslide Hazards Program mission is focused on understanding ground failure hazards to reduce long-term losses and protect people and property. For postfire debris flows, hazard assessments are performed using operational models to estimate the likelihood of debris-flow initiation (Staley et al., 2017) and the magnitude of debris-flow volume (Gartner et al., 2014). These models are used to rapidly generate hazard assessment maps that are made available online. This opportunity is aimed at research to inform several emerging priorities related to postfire debris-flow hazards that will refine or result in new operational products.
We seek a Mendenhall Fellow who will advance postfire debris-flow research in one of four key areas: (1) understanding the dynamics and the hazard posed by debris-flow runout, (2) determining the controls on debris-flow volume, (3) identifying how debris-flow initiation and volume change with time since fire, or (4) determining the regional climate controls on postfire debris-flow hazards and how patterns will shift with climate change. We expect a successful candidate will contribute research that fundamentally advances our understanding of the hazard, develops new approaches for operational hazard assessment, or refines existing operational models.
The first area of potential research is in debris-flow runout modeling. Currently, the USGS does not have an operational debris-flow runout model that can quickly estimate where debris flows will move once they are initiated. We seek proposals that may contribute to any of the following areas: (1) Evaluating the performance of existing runout models in the context of past events; (2) Understanding the uncertainty characteristics of debris-flow runout forecasts; (3) Developing and testing frameworks for forecasting runout; (4) Developing field or laboratory methods that can inform the parameterization of debris-flow mobility in runout models.
The second area of potential research is understanding the controls on debris-flow volume. Recent research has suggested that debris-flow volume is the most critical parameter for runout modeling (Barnhart et al., 2021), and therefore efforts to develop more accurate postfire debris-flow volume models would be beneficial. The current operational volume model performs well in the region where it was developed (southern CA) (Rengers et al., 2021), but new data shows it overpredicts debris-flow volumes in other regions of the western USA. We seek proposals that contribute to any of the following areas: (1) What fundamental physical processes contribute to the recruitment of sediment by debris flows? (2) How does the volume of sediment recruited by debris flows vary across different regions in the US? (3) What controls the dynamics of debris-flow storage in channels and potential remobilization? (4) How can estimates of sediment depletion be used to update debris-flow likelihood estimates?
The third area of potential research is understanding how debris-flow initiation processes and volume change with time since fire. Current USGS operational models for debris-flow initiation and volume would benefit from research that helps to account for temporal changes in hydrologic and sedimentation processes after wildfire. One example of a temporal change after wildfire is recent work showing that the debris-flow initiation process can shift due to vegetation regrowth and hydrologic recovery (Thomas et al., 2021). In semi-arid climates immediately after fire, runoff-initiated debris flows are initiated on hillslopes and grow substantially as they move downstream entraining sediment (McGuire et al., 2016). However, several years after wildfire, shallow-landslide initiated debris flows with a shorter runout can occur (Meyer et al., 2001; Rengers et al., 2020). The shift in initiation mechanics alters the triggering rainfall thresholds and the volume and mobility of the flow. We seek proposals that define process changes with time since fire, such as this example. Additional research may contribute to the following areas: (1) What controls the transition from runoff-initiated to shallow-landslide initiated debris flows? (2) How mobile are debris flow in drainages that have experienced vegetation recovery? (3) How does sediment availability change over time? (4) What is the effect of decaying root strength on landsliding? (5) How does vegetation regrowth affect debris-flow hazards?
The final area of research is how debris-flow initiation mechanisms vary with regional climate, and future climate change. For example, historically there have been relatively few documented runoff-initiated debris flows in wet regions, such as the Pacific Northwest (PNW) (Wondzell & King, 2003). Wildfire effects in the PNW were primarily shown to induce dry ravel (Roering & Gerber, 2005) and shallow landsliding due to root-decay (Jackson & Roering, 2009). There have been recent large fires in wet regions of the PNW (Abatzoglou et al., 2021) and Appalachian mountains (James et al., 2020), and debris flows have been observed following these fires. Understanding how regional climate variations result in triggering conditions for postfire debris flows could help with developing regionally specific hazard assessments. It could also show how debris-flow hazards will shift with climate change. We seek proposals that may contribute to the following areas: (1) What are the dominant meteorologic phenomena in different regions that trigger postfire debris flows (atmospheric rivers, monsoonal activity, etc.) and the seasons when those storms might be expected?; (2) How will the frequency, magnitude, and seasonality of postfire debris-flow susceptibility change under a warming climate?
This research opportunity can capitalize on a rich data set documenting postfire hydrologic and debris-flow response of recently burned watersheds in the western United States. The researcher would be expected to utilize skill sets including numerical modeling, advanced geospatial analysis, quantitative geomorphology and hydrology, and assessment of geologic hazards. The postdoctoral fellow will have the opportunity to engage a research team of both USGS scientists and academic collaborators. Finally, the project will involve high levels of engagement with collaborators at the National Weather Service, U.S. Forest Service, various State Geological Surveys, and faculty and students at Colorado School of Mines.
Interested applicants are strongly encouraged to contact the Research Advisors early in the application process to discuss project ideas.
Abatzoglou, J. T., Rupp, D. E., O’Neill, L. W., & Sadegh, M. (2021). Compound extremes drive the western Oregon wildfires of September 2020. Geophysical Research Letters, 48(8), e2021GL092520.
Barnhart, K. R., Jones, R. P., George, D. L., McArdell, B. W., Rengers, F. K., Staley, D. M., & Kean, J. W. (2021). Multi-Model Comparison of Computed Debris Flow Runout for the 9 January 2018 Montecito, California Post-Wildfire Event. Journal of Geophysical Research: Earth Surface, 126(12), e2021JF006245.
Gartner, J. E., Cannon, S. H., & Santi, P. M. (2014). Empirical models for predicting volumes of sediment deposited by debris flows and sediment-laden floods in the transverse ranges of southern California. Engineering Geology, 176, 45–56.
Hill, J. S., Douglas, T. J., Korte, D. M., Scheip, C. M., Wooten, R. M., & Palmer, J. M. (2020). Debris Flows triggered by August 24, 2019 Storm in the Nantahala Gorge, Western North Carolina; Did the Underlying Bedrock and the 2016 Wildfires Increase Landslide Susceptibility. Geological Society of America Abstracts with Programs, 52(2). https://doi.org/10.1130/abs/2020SE-344730
Jackson, M., & Roering, J. J. (2009). Post-fire geomorphic response in steep, forested landscapes: Oregon Coast Range, USA. Quaternary Science Reviews, 28, 1131–1146. https://doi.org/10.1016/j.quascirev.2008.05.003
James, N. A., Abt, K. L., Frey, G. E., Han, X., & Prestemon, J. P. (2020). Fire in the Southern Appalachians: Understanding impacts, interventions, and future fire events. United States Department of Agriculture, Forest Service, Southern Research ….
Kostelnik, J., Burns, W., Calhoun, N., & Rengers, F. (2022). Columbia River Gorge Landslides. https://landslides.usgs.gov/storymap/eagle-creek/
McGuire, L. A., Kean, J. W., Staley, D. M., Rengers, F. K., & Wasklewicz, T. A. (2016). Constraining the relative importance of raindrop-and flow-driven sediment transport mechanisms in postwildfire environments and implications for recovery time scales. Journal of Geophysical Research: Earth Surface, 121(11), 2211–2237.
Meyer, G. A., Pierce, J. L., Wood, S. H., & Jull, A. T. (2001). Fire, storms, and erosional events in the Idaho batholith. Hydrological Processes, 15(15), 3025–3038.
Rengers, F. K., McGuire, L. A., Kean, J. W., Staley, D. M., Dobre, M., Robichaud, P. R., & Swetnam, T. (2021). Movement of sediment through a burned landscape: Sediment volume observations and model comparisons in the San Gabriel Mountains, California, USA. Journal of Geophysical Research: Earth Surface, 126(7), e2020JF006053.
Rengers, F. K., McGuire, L. A., Oakley, N. S., Kean, J. W., Staley, D. M., & Tang, H. (2020). Landslides after wildfire: Initiation, magnitude, and mobility. Landslides, 17(11), 2631–2641.
Roering, J. J., & Gerber, M. (2005). Fire and the evolution of steep, soil-mantle landscapes. Geology, 33, 349–352.
Staley, D. M., Negri, J. A., Kean, J. W., Laber, J. L., Tillery, A. C., & Youberg, A. M. (2017). Prediction of spatially explicit rainfall intensity–duration thresholds for post-fire debris-flow generation in the western United States. Geomorphology, 278, 149–162.
Thomas, M. A., Rengers, F. K., Kean, J. W., McGuire, L. A., Staley, D. M., Barnhart, K. R., & Ebel, B. A. (2021). Postwildfire soil-hydraulic recovery and the persistence of debris flow hazards. Journal of Geophysical Research: Earth Surface, 126(6), e2021JF006091.
Wondzell, S. M., & King, J. G. (2003). Postfire erosional processes in the Pacific Northwest and Rocky Mountain regions. Forest Ecology and Management, 178(1–2), 75–87.
Proposed Duty Station(s)
Areas of PhD
Geology, geomorphology, geophysics, hydrology, hydrometeorology, engineering geology or related fields (candidates holding a Ph.D. in other disciplines, but with extensive knowledge and skills relevant to the Research Opportunity may be considered).
(This type of research is performed by those who have backgrounds for the occupations stated above. However, other titles may be applicable depending on the applicant's background, education, and research proposal. The final classification of the position will be made by the Human Resources specialist.)