28. Quantitative Forecasting of Debris-Flow and Debris-Avalanche Hazards

Debris flows and avalanches are the most pervasive and destructive geologic hazard in many mountainous areas. They pose particularly severe threats in tectonically active areas with an abundance of unconsolidated sediment and weak rock (e.g., the flanks of stratovolcanoes). Field investigations are critical for recognizing the existence of debris-flow and avalanche hazards, but quantitative models are necessary for making objective, reproducible hazard forecasts. The focus of this research involves development and testing of state-of-the-art models for hazard forecasting, which is a priority of the USGS.

Several computational and statistical models developed by USGS scientists during the past decade provide tools for debris-flow and avalanche hazard forecasting, but the tools remain incomplete. For example, the statistically based model LAHARZ (Iverson et al., 1998) has been widely used for forecasting areal limits of lahar inundation, but it provides no explicit means of linking hazard potential to geological and hydrological attributes of specific sites. Physically based, quasi-three-dimensional models of slope failure and downslope runout have more explicit predictive power and have the potential for application to a wide range of earth-surface flow phenomena, including dam-break water floods. However, such models but have not yet been widely utilized for hazard assessment owing to three key problems that must be overcome. This research will address one or more of these problems:

1. Downstream hazards can be greatly influenced by entrainment of debris along the flow path, because such entrainment can cause flow volumes to multiply many times in transit Although the mathematical basis for including debris entrainment in flow-dynamics models is well-established, an outstanding need exists to relate entrainment potential to flow-path topography and physical properties of substrate sediment and rock. Solution of this problem will require a combination of field observations, theoretical analysis, computational modeling, and experimental tests.
2. Grain-size segregation that occurs during motion of debris flows and avalanches has large ramifications for runout dynamics. Size segregation coupled with pore-pressure evolution can cause significant redistribution of frictional resistance, and this redistribution affects the velocity and ultimate runout distance of the moving mass. Current flow-dynamics models have no means of incorporating size-segregation effects in their continuum mechanical frameworks. A need exists to perform experimental, theoretical, and computational work to meld models of the grain-scale physics of size segregation with models of the continuum-scale physics of runout. Better understanding of the mechanisms of grain-size segregation will also enhance sedimentological interpretation of mass-flow deposits.
3. Flow-dynamics models require specification of the initial position, volume, shape, and pore-pressure distribution of the potentially unstable mass. These attributes can be inferred from repetitive applications of three-dimensional slope-stability models, but no computational framework exists for integrating flow-dynamics models and slope-stability models. There is an important, unmet need for development of a combined slope-failure/runout model that enables computation of the entire history of a hazardous event, from slope failure to downstream deposition.

A unique resource available to facilitate this work is the USGS debris-flow flume, operated by the Cascades Volcano Observatory and located east of Eugene, Oregon. (See a description at http://vulcan.wr.usgs.gov/Projects/MassMovement/). Flume experiments with large (10 m³) flowing masses of sediment and water provide data necessary for formulating and testing models of debris flows and avalanches. Additional, small-scale experiments can be conducted using laboratory facilities available at the Cascades Volcano Observatory.

Applicants should possess quantitative skills in (A) classical and continuum mechanics, with preference given to candidates with knowledge that includes solid-fluid mixture mechanics (e.g., soil mechanics); and (B) computational solution of differential equations, with preference given to candidates with knowledge that includes finite-volume methods for systems of hyperbolic conservation laws. Applicants should also possess general familiarity and knowledge of geological and hydrological processes that operate at or near Earth's surface.

Some recent publications by the Research Advisors provide a foundation for the proposed work:

Denlinger, R.P., and Iverson, R.M., 2001, Flow of variably fluidized granular masses across three-dimensional terrain: 2. Numerical predictions and experimental tests: Journal of Geophysical Research, v. 106, no. B1, p. 553-566.

Denlinger, R.P., and Iverson, R.M., 2004, Granular avalanches across irregular three-dimensional terrain: 1. theory and computation: Journal of Geophysical Research, v. 109, F01014, 14 p.

Iverson, R.M., 1997, The physics of debris flows: Reviews of Geophysics, v. 35, p. 245-296.

Iverson, R.M., 2000, Landslide triggering by rain infiltration: Water Resources Research, v. 36, p. 1897-1910.

Iverson, R.M., in press, Forecasting runout of rock and debris avalanches: Proceedings of the NATO Advanced Research Workshop on Massive Rock Slope Failure, Celano, Italy, 2002.

Iverson, R.M., and Denlinger, R.P., 2001, Flow of variably fluidized granular masses across three-dimensional terrain: 1. Coulomb mixture theory: Journal of Geophysical Research, v. 106, no. B1, p. 537-552.

Iverson, R.M., and Vallance, J.W., 2001, New views of granular mass flows: Geology, v. 29, no. 2, p. 115-118.

Iverson, R.M., Reid, M.E., and LaHusen, R.G., 1997, Debris-flow mobilization from landslides: Annual Review of Earth and Planetary Sciences, v. 25, p. 85-138.

Iverson, R.M., Schilling, S.P., and Vallance, J.W., 1998, Objective delineation of lahar-inundation hazard zones: Geological Society of America Bulletin, v. 110, p. 972-974.

Iverson, R.M., Reid, M.E., Iverson, N.R., LaHusen, R.G., Logan, M., Mann, J.E., and Brien, D.L., 2000, Acute sensitivity of landslide rates to initial soil porosity: Science, v. 290, p. 513-516.

Iverson, R.M., Logan, M., and Denlinger, R.P., 2004, Granular avalanches across irregular three-dimensional terrain: 2, Experimental tests: Journal of Geophysical Research, v. 109, F01015, 16 p.

Reid, M.E., Christian, S.B. and Brien, D.L., 2000, Gravitational stability of three-dimensional stratovolcano edifices: Journal of Geophysical Research, v. 105, p. 6043-6056.

Reid, M.E., Sisson, T.W., and Brien, D.L., 2001, Volcano collapse promoted by hydrothermal alteration and edifice shape, Mount Rainier, Washington: Geology, v. 29, p. 779-782.

Proposed Duty Station: Vancouver, WA or Menlo Park, CA

Areas of Ph.D.: Earth science (geology, hydrology, oceanography, geophysics), physics, engineering, applied mathematics

Qualifications: Applicants must meet one of the following qualifications: Research Geologist, Research Geophysicist, Research Hydrologist, Research Hydraulic Engineer, Physical Scientist, Research Physicist, Research Mathematician

(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 Personnel specialist.)

Research Advisor(s): Richard Iverson, (360) 993-8920, riverson@usgs.gov; Roger Denlinger, (360) 993-8904, roger@usgs.gov; Mark Reid, (650) 329-4891, mreid@usgs.gov

Personnel Office contact: Marie Guillory, (650) 329-4112, guillory@usgs.gov

Summary of Opportunities