Allen C. Gellis, Research Hydrologist-Geomorphologist

Education

Ph.D.

Ph.D. Colorado State University (2003) - Geology - Dissertation Title: Suspended-Sediment Characteristics In Four Humid Tropical Watersheds Of Contrasting Land Use, Puerto Rico

M.S.

Colorado State University (1986) - geology

B.S.

State University of New York at Albany (1981) - geology

Current Research

My research interests are in geomorphic areas of sediment transport, sediment provenance, upland erosion, and channel change. My research in Maryland is focusing on understanding the sources and flux of suspended sediment in select watersheds draining to the Chesapeake Bay. This data will coincide with other USGS efforts to understand sediment processes in the tidal portions of Chesapeake Bay that include shoreline erosion, sediment transport in the Bay, and sediment resuspension in the Bay. Information from all these sediment processes will be used to understand the relation of sediment delivery to sediment deposition, effects on water clarity, and effects on submerged aquatic vegetation and other biota in the receiving tidal tributaries.

My research on arroyo systems in the Southwest has focused on examining arroyo cut-and-fill cycles in the Late Quaternary, documenting arroyo channel changes in the historic record (last 100 years), and applying knowledge of arroyo dynamics and hillslope erosion to watershed rehabilitation strategies. Interpretation made from my research suggests that over geologic time scales (~10,000 years) intrinsic processes may dictate when conditions are right for arroyo cutting. Depending on the state of channel conditions (depth, width, channel slope, vegetation, etc.) the arroyo may not have the correct hydraulic conditions necessary for a climate change to trigger incision. This hypothesis that the state of the arroyo is important is further supported by my research on recent arroyo changes and climate changes in New Mexico. For more information on my arroyo research go to the site http://climchange.cr.usgs.gov/rio_puerco/erosion/yields.html

Photograph of Arroyo Chavez, an incised channel in New Mexico that was the focus of erosion studies.

I am also studying suspended-sediment characteristics in humid-tropical watersheds in Puerto Rico. The objectives of this research are to understand the significant hydrologic controls of suspended-sediment concentration and how previous events affect sediment concentrations. I am also interested in how these controls on sediment characteristics will change in basins of differing land use (forest pasture, cropland, and urban).

Hypothetical model of sediment availability through time in response to storm events and between storm events for a) an undisturbed basin and b) a disturbed basin in Puerto Rico.

Selected Publications

Gellis, A.C., 2002, Twentieth Century Channel Changes in Chaco Culture National Historic Park: U.S. Geological Survey Water-Investigations Report 01-4251, 42 p.

Gellis, A.C., and Elliott, J.G., 2001, Arroyo changes in selected watersheds of New Mexico, United States: In Harvey, M., and Anthony, D., eds., Applying Geomorphology to Environmental Management, A Special Publication Honoring Stanley A. Schumm, Water Resources Publications, LLC Press, p. 225-240.

Gellis, A.C., Pavich, M.J., and Ellwein, A., 1991, Erosion and sediment yields in two subbasins of contrasting land use, Rio Puerco, New Mexico: Proceedings of the Seventh Federal Interagency Sedimentation Conference, Reno, Nevada, p. V83-V90.

Gellis, A.C, 2001, Factors controlling storm-generated suspended-sediment concentrations and loads in a humid-tropical basin, Quebrada Blanca, Puerto Rico: Proceedings of the Seventh Federal Interagency Sedimentation Conference, Reno, Nevada, p. V91-V98.

Gellis, A.C., Cheama, A., and Lalio, S.M., 2001, Developing an approach for ranking watersheds for rehabilitation, Zuni Indian Reservation, New Mexico: Geomorphology, v. 37, p. 105-134.

Gellis, A.C., Webb, R.M.T., Wolfe, W.J., and McIntyre, S.C.I., 1999, Effects of land use on upland erosion, sediment transport, and reservoir sedimentation, Lago Loiza basin, Puerto Rico: U.S. Geological Survey Water-Resources Investigations Report 99-4010, 60 p.

Elliott, J.G., Gellis, A.C., and Aby, S.B., 1999, Evolution of Arroyos--Incised Channels of the Southwestern United States: In Darby, S.E., and Simon, A., eds., Incised Channels--Processes, Forms, Engineering and Management, p. 153-185.

Gellis, A.C., 1998, Characterization and evaluation of channel and hillslope erosion on the
Zuni Reservation, 1992-95: U.S. Geological Survey Water-Resources Investigations Report 97-4292, 51 p.

Gellis, A.C., 1998, Surface-water and suspended-sediment inflow and outflow for Nutria Reservoir No. 3, Zuni Indian Reservation, New Mexico, March 1994 to September 1995: U.S. Geological Survey Water-Resources Investigations Report 98-4083, 22p.

Gellis, A.C., Andres, C., Lalio, S., and Enote, J., 1997, Selecting a watershed for rehabilitation at the Zuni Reservation. Watershed and Wet Weather Technical Bulletin, v.1, no. 1, p. 9-12.

Gellis, A.C., Andres, C., Lalio, S., and Enote, J., 1996, An approach to selecting a watershed for rehabilitation developed for the Zuni Reservation, New Mexico: Watershed 96 Proceedings, Baltimore, MD., June 8-12, 1996, p.360-363.

Gellis, A.C., 1996, Gullying at the Petroglyph National Monument, New Mexico: Journal of Soil and Water Conservation, v.51, no.2, p.155-159.

Gellis, A.C., Cheama, A., Laahty, V., and Lalio, S., 1995, Assessment of gully-control structures in the Rio Nutria watershed, Zuni Reservation, New Mexico: Water Resources Bulletin, v. 31, no. 4, p. 633-636.

Gellis, A.C., 1995, Erosion assessment at the Petroglyph National Monument area, Albuquerque, New Mexico: U.S. Geological Survey Water-Resources Investigations Report 94-4205, 39pp.

Gellis, A.C., 1993, The effects of Hurricane Hugo on suspended-sediment loads, Lago Loíza basin, Puerto Rico: Earth Surface Processes and Landforms, v .18, no. 5. p. 505-517.

Gellis, A.C., 1992, Decreasing trends of suspended-sediment loads in selected streamflow stations in New Mexico: New Mexico Water Resources Research Institute Report No. 265, Proceedings of the 36th Annual New Mexico Water Conference, Las Cruces, N.Mex., p. 77-93.

Gellis, A.C., 1991, Construction effects on sediment for two basins, Puerto Rico: Proceedings of the Fifth Federal Interagency Sedimentation Conference, Las Vegas, Nev., chap. 4, p. 72-78.

Gellis, A.C., Hereford, R., Schumm, S.A., and Hayes, B.R., 1991, Channel evolution and hydrologic variations in the Colorado River basin--Factors influencing sediment and salt loads: Journal of Hydrology, v. 124, p. 317-344.

Schumm, S.A., and Gellis, A.C., 1989, Sediment yield variations as a function of incised channel evolution, in Brush, L.M. et.al., eds., Taming the Yellow River--Silt and floods: Kluwer Academic Publishers, p. 99-109.

Gellis, A.C., Hereford, R., and Schumm, S.A., 1989, Geomorphic and hydrologic control of sediment and salt loads in the Colorado River basin--Significance for conservation and land management: U.S. Geological Survey Open-File Report 89-121, 36 p.

Gellis, A.C., 1988, Decreasing sediment and salt loads in the Colorado River basin--A response to arroyo evolution: Fort Collins, Colo., Colorado State University, unpublished M.S. thesis, 178 p.