Peter Griffiths

Education

1987

B.A., Yale University
Major: Archeological Studies

1995

M.S., University of Arizona
Major: Geosciences
Minor: Hydrology

Research Summary

I have been a research hydrologist/geomorphologist with the U.S. Geological Survey for more than fifteen years. Over that time, my research has focused on issues of mass-movement and sediment transport in the southwestern United States. Among my particular interests are the frequency, processes of initiation, and geomorphic impact of debris flows, particularly along the canyons of the Colorado River system. My methods typically involve the collection and analysis of geospatial data and the modeling of landscape processes. I also investigate sediment yield and transport in small drainage basins in arid environments, often making use of naturally-occurring radioisotopes to track sediment movement and date deposits. My most recent work has involved the application of weather radar data to the study of debris-flow initiation in southern Arizona, and the use of wind-shaped plants (Larrea tridentata) to map the movement of aeolian sand in the northern Coachella Valley.

Bibliography

Melis, T.S., Webb, R.H., Griffiths, P.G., and Wise, T.J., 1994, Magnitude and frequency data for historic debris flows in Grand Canyon National Park and vicinity, Arizona: U.S. Geological Survey Water Resources Investigations Report 94-4214, 285 p.

Griffiths, P.G., Webb, R.H., and Melis, T.S., 1996, Initiation and frequency of debris flows in Grand Canyon, Arizona: U.S. Geological Survey Open-File Report 96-491, 35 p.

Webb, R.H., Melis, T.S., Griffiths, P.G., and Elliott, J.G., 1997, Reworking of aggraded debris fans by the 1996 controlled flood on the Colorado River in Grand Canyon National Park, Arizona: U.S. Geological Survey Open-file Report 97-16, 40 p.

Griffiths, P.G., Webb, R.H., and Melis, T.S., 1997, Initiation of debris flows in bedrock canyons of the Colorado River, USA, in Chen, Cheng-lung (editor), Debris-flow hazards mitigation: Mechanics, prediction, and assessment: New York, American Society of Civil Engineers, p. 12-20.

Melis, T.S., Webb, R.H., and Griffiths, P.G., 1997, Debris flows in Grand Canyon National Park: Peak discharges, flow transformations, and hydrographs, in Chen, Cheng-lung (editor), Debris-flow hazards mitigation: Mechanics, prediction, and assessment: New York, American Society of Civil Engineers, p. 727-736.

Webb, R.H., Griffiths, P.G., Melis, T.S., Elliott, J.G., and Pizzuto, J.E., 1999, Reworking of debris fans by the 1996 controlled flood in Grand Canyon, in Webb, R.H., Schmidt, J.C., Valdez, R.A., and Marzolf, G.R., The 1996 flood in Grand Canyon: Scientific experiment and management demonstration: Washington, D.C. American Geophysical Union, Geophysical Monograph, p. 37-51.

Pizzuto, J.E., Webb, R.H., Griffiths, P.G., Elliott, J.G, and Melis, T.S., 1999, Entrainment and transport of cobbles and boulders from debris fans, in Webb, R.H., Schmidt, J.C., Marzolf, G.R., and Valdez, R.A., The controlled flood in Grand Canyon: Scientific experiment and management demonstration: Washington, D.C. American Geophysical Union, Geophysical Monograph 110, p. 53-70.

Webb, R.H., Melis, T.S., Griffiths, P.G., Elliott, J.G., Cerling, T.E., Poreda, R.J, Wise, T.W., and Pizzuto, J.E., 1999, Lava Falls Rapid in Grand Canyon, Effects of late Holocene debris flows on the Colorado River: U.S. Geological Survey Professional Paper 1591, 90 p.

Webb, R.H., Griffiths, P.G., Melis, T.S., and Hartley, D.R., 2000, Sediment delivery by ungaged tributaries of the Colorado River in Grand Canyon: U.S. Geological Survey Water Resources Investigations Report 00-4055, 67 p. http://wwwpaztcn.wr.usgs.gov/webb_pdf/wrir00-4055.pdf

Webb, R.H., Griffiths, P.G., and Hartley, D.R., 2001, Techniques for estimating sediment yield of ungaged tributaries on the southern Colorado Plateau: Reno, Nevada, Proceedings of the Seventh Federal Interagency Sedimentation Conference, p. I-24 to I-31.

Webb, R.H., and Griffiths, P.G., 2001, Sediment delivery by ungaged tributaries of the Colorado River in Grand Canyon: U.S. Geological Survey Fact Sheet FS-018-01, 4 p. http://pubs.usgs.gov/fs/FS-018-01/

Webb, R.H., and Griffiths, P.G., 2001, Monitoring of coarse sediment inputs to the Colorado River in Grand Canyon: U.S. Geological Survey Fact Sheet FS-019-01, 4 p. http://pubs.usgs.gov/fs/FS-019-01/

Griffiths, P.G., Webb, R.H., Lancaster, N., Kaehler, C.A., and Lundstrom, S.C., 2002, Long-term sand supply to Coachella Valley fringe-toed lizard (Uma inornata) habitat in the northern Coachella Valley, California: U.S. Geological Survey Water-Resources Investigations Report 02-4013, 49 p. http://pubs.er.usgs.gov/usgspubs/wri/wri024013

Webb, R.H., Melis, T.S., and Griffiths, P.G., 2003, Debris flows and the Colorado River, in Beus, S.S., and Morales, M., Grand Canyon Geology, 2nd edition: New York, Oxford University Press, p. 371-390.

Webb, R.H., Griffiths, P.G., and Melis, T.S., 2004, Debris flows and rapids in Grand Canyon: Implications for erosion rates and evacuation of sediment from tributary canyons, in Young, R.A., and Spamer, E.E. (eds.), 2001, The Colorado River: Origin and evolution: Grand Canyon, Arizona, Grand Canyon Association Monograph 12, p. 183-188.

Griffiths, P.G., Webb, R.H., and Melis, T.S., 2004, Initiation and frequency of debris flows in Grand Canyon, Arizona: Journal of Geophysical Research, Earth Surface, v. 109, F04002, doi:10.1029/2003JF000077, 14 p.

Webb, R.H., Griffiths, P.G., Magirl, C.S., and Hanks, T.C., 2005, Debris flows in Grand Canyon and the rapids of the Colorado River, in Gloss, S.P., Lovich, J.E., and Melis, T.S. (eds.), The State of the Colorado River Ecosystem in Grand Canyon: U.S. Geological Survey Circular 1282, p. 119-132. http://pubs.er.usgs.gov/usgspubs/cir/cir1282

Griffiths, P.G., Hereford, R., and Webb, R.H., 2005, Sediment yield and runoff frequency from small drainages in the Mojave Desert: Geomorphology, v. 74, p. 232-244.

Magirl, C.S., Webb, R.H., and Griffiths, P.G., 2005, Long-term change in the water-surface profile of the Colorado River in Grand Canyon, Arizona: Water Resources Research, v. 41, W05021, doi:10.1029/2003WR002519, 10 p.

Griffiths, P.G., Hereford, R., and Webb, R.H., 2006, Sediment yield and runoff frequency of small drainage basins in the Mojave Desert, California and Nevada: U.S. Geological Survey Fact Sheet 2006-3007, 4 p. http://pubs.usgs.gov/fs/2006/3007/

Magirl, C.S., P.G. Griffiths, and R.H. Webb, 2006, “ADV point measurements within rapids of the Colorado River in Grand Canyon,” in Graham, R. (editor), Examining the Confluence of Environmental and Water Concerns, Proceedings of the 2006 World Environmental and Water Resources Congress, Omaha, Nebraska, May 21-25, 2006: Reston, Virginia, American Society of Civil Engineers Publication, 10 p.

Yanites, B.J., Webb, R.H., Griffiths, P.G., and Magirl, C.S., 2006, Debris-flow deposition and reworking by the Colorado River in Grand Canyon, Arizona, Water Resources Research, v. 42, W11411, doi:10.1029/2005WR004847, 16 p.

Magirl, C.S., C. Shoemaker, R.H. Webb, M. Schaffner, P.G. Griffiths, E. Pytlak, 2007, “Debris flows and record floods from extreme mesoscale convective thunderstorms over the Santa Catalina Mountains, Arizona,” U.S. Geological Survey Open-File Report 2007-1108, 1 sheet. http://pubs.usgs.gov/of/2007/1108/

Magirl, C.S., R.H. Webb, M. Schaffner, S.W. Lyon, P.G. Griffiths, C. Shoemaker, C.L. Unkrich, S. Yatheendradas, P.A. Troch, E. Pytlak, D.C. Goodrich, S.L.E. Desilets, A. Youberg, and P.A. Pearthree, 2007, “Impact of recent extreme Arizona storms,” Eos Transactions, American Geophysical Union, Vol. 88, No. 17, pp. 191, 193. http://www.agu.org/pubs/crossref/2007/2007EO170003.shtml

Webb, R.H., Griffiths, P.G., Wallace, C.S.A., and Boyer, D.E., 2007, Channel response to low-elevation desert fire: the King Valley fire of 2005: U.S. Geological Survey Report Series Data-DS 275, 52 p. http://pubs.usgs.gov/ds/2007/275/

Magirl, C.S., Breedlove, M.J., Webb, R.H., and Griffiths, P.G., 2008, Modeling water-surface elevations and virtual shorelines for the Colorado River in Grand Canyon, Arizona: U.S. Geological Survey Scientific Investigation Report 2008-5075, 32 p. http://pubs.er.usgs.gov/usgspubs/sir/sir20085075

Webb, R.H., Griffiths, P.G., and Rudd, L.P., 2008, Occurrence of debris flows on the Colorado Plateau: the influence of clay mineralogy and chemistry, Geological Society of America Bulletin, vol. 120, No. 7/8, p. 1010-1020. http://gsabulletin.gsapubs.org/content/vol120/issue7-8/index.dtl

Webb, R.H., Magirl, C.S., Griffiths, P.G., and Boyer, D.E., 2008, Debris flows and floods in southeastern Arizona from extreme precipitation in July 2006: magnitude, frequency, and sediment delivery: U.S. Geological Survey Open-File Report 2008-1274, 95 p. http://pubs.usgs.gov/of/2008/1274/

Webb, R.H., Magirl, C.S., Griffiths, P.G., Youberg, A., and Pearthree, P.A., 2008, Slopes fail, debris flows in extremis: Southwest Hydrology, v. 7, p. 8. http://www.swhydro.arizona.edu/archive/V7_N6/dept-ontheground.pdf

Griffiths, P.G., Magirl, C.S., Webb, R.H., Pytlak, E., Troch, P.A., Lyon, S.W., 2009, Spatial distribution and frequency of precipitation during an extreme event: the July 2006 mesoscale convective complexes and floods in southeastern Arizona, Water Resources Research, 36 p., in press.

Griffiths, P.G., Webb, R.H., Muth, A, Fisher, M., in preparation, Plant and ventifacts delineate late Holocene high wind vectors in the Coachella Valley, U.S.A., Aeolian Research, 31 p., in review.