Mendenhall Research Fellowship Program

S55. Streamflow, sediment, and morphodynamic modeling of the Colorado River in Grand Canyon


Closing Date: June 14, 2021

This Research Opportunity will be filled depending on the availability of funds. All application materials must be submitted through USAJobs by 11:59 pm, US Eastern Standard Time, on the closing date.



A variety of predictive models for streamflow and sediment transport are used for both research and planning purposes on the Colorado River in Grand Canyon. An unsteady kinematic-wave flow model (Wiele and Griffin, 1997) is used to predict discharge for steady and unsteady (fluctuating) flows. This model is incorporated in a model that routes sand between gaging stations located 30- to 60-miles apart (Wright and others, 2010) that is used by management agencies to plan and design controlled floods. A second 1-dimensional flow model was developed by Magirl and others (2008) to predict water surface elevation for steady flow conditions at ~0.1-mile increments for the entire 225-mile segment between Lees Ferry and Diamond Creek (Magirl et al., 2005). This model is currently used by management agencies to predict areas that are inundated by controlled floods and other releases.

While the above large-scale models are used for management and planning, a collection of reach-scale 2- and 3-dimensional models have been developed to address specific research questions. Two-dimensional morphodynamic models have been used to estimate rates of sandbar deposition in lateral flow recirculation zones (eddies) for controlled floods (Wiele et al., 1999; Logan et al., 2010; Sloff et al., 2012). Because boundary conditions are difficult to parameterize and because some processes, such as subaqueous mass failures, are not modeled, these models have had limited predictive capability (Logan et al., 2010; Sloff et al., 2009, 2012). More highly-resolved 3-dimensional models have been shown to produce good representations of turbulent flow structures in eddies (Alvarez et al., 2017); however, computational expense has prevented the extension of these models to produce morphodynamic predictions.

Despite the level of past effort, there remain management information needs that are not met by current models and new research opportunities are afforded by the growing amount of sediment transport (Topping and Wright, 2016) and channel geometry (e.g., Grams et al., 2019) data. Although much of the management of the Colorado River in Grand Canyon has been focused on the supply and transport of sand-sized material, the transport of finer suspended sediment (silt and clay) is of increasing interest because it contributes substantially to turbidity which impacts both native and nonnative fish (Ward et al., 2016). However, incorporation of silt and clay in transport models will require major revisions to the current models, because they were developed and calibrated strictly for sand-sized sediment (Wright et al., 2010).

There is also strong interest in coupling predictions of sand transport and sand budgets (e.g. Wright et al., 2010) with predictions of sandbar response to flows, such as controlled floods (e.g. Mueller et al., 2014; 2018). Such predictions of sandbar response would be extremely valuable to managers in evaluating trade-offs for potential dam-release scenarios. Wiele et al. (2007) developed an approach to parameterize a 1-dimensional model to predict sandbar response, but differences between the resolution of model predictions (very fine) and verification data (coarse) were a challenge for model verification and implementation. However, with the addition of more than 15 years of sediment transport data (Topping and Wright, 2016; Rubin et al., 2020) and sandbar measurements (Mueller et al., 2018), an approach similar to that proposed by Wiele et al. (2007) or slightly different approach based on that of Andrews and Vincent (2007) may now be realistic.


The proposed study will develop numerical models that expand current capabilities for prediction of sand transport in the supply-limited Grand Canyon to include transport of silt and clay. The proposed study will also develop methods to parameterize the exchange of suspended material (sand and silt/clay) between the main channel of the Colorado River and lateral flow recirculation zones (eddies).

Anticipated Skillsets

It is anticipated that the successful applicant will have strong computing skills and extensive experience with numerical modeling of physical processes. Experience with scientific instrumentation associated with river-related field work or laboratory flume experimentation is also expected. Programming skills, experience with spatial datasets, and experience with cloud computing are desired. These skills and experience should be reflected in the research proposal and/or the resume.

Interested applicants are strongly encouraged to contact the Research Advisor(s) early in the application process to discuss project ideas.


Alvarez, L. V., Schmeeckle, M.W., Grams, P.E., 2017. A detached eddy simulation model for the study of lateral separation zones along a large canyon-bound river. J. Geophys. Res. Earth Surf. 122, 25–49.

Logan, B., Nelson, J., McDonald, R., Wright, S., 2010. Mechanics and modeling of flow, sediment transport and morphologic change in riverine lateral separation zones, in: 2nd Joint Federal Interagency Conference. Las Vegas, NV, p. 2255.

Magirl, C.S., Webb, R.H., Griffiths, P.G., 2005. Changes in the water surface profile of the Colorado River in Grand Canyon, Arizona, between 1923 and 2000. Water Resour. Res. 41,

Magirl, C.S., Webb, R.H., Griffiths, P.G., 2008. Modeling water-surface elevations and virtual shorelines for the Colorado River in Grand Canyon, Arizona. U.S. Geol. Surv. Sci. Investig. Rep. 2008-5075 32.

Mueller, E.R., Grams, P.E., Hazel, J.E., Schmidt, J.C., 2018. Variability in eddy sandbar dynamics during two decades of controlled flooding of the Colorado River in the Grand Canyon. Sediment. Geol. 363, 181–199.

Mueller, E.R., Grams, P.E., Schmidt, J.C., Hazel, J.E., Alexander, J.S., Kaplinski, M., 2014. The influence of controlled floods on fine sediment storage in debris fan-affected canyons of the Colorado River basin. Geomorphology 226, 65–75.

Rubin, D.M., Buscombe, D., Wright, S.A., Topping, D.J., Grams, P.E., Schmidt, J.C., Hazel Jr., J.E., Kaplinski, M.A., Tusso, R., 2020. Causes of Variability in Suspended-Sand Concentration Evaluated Using Measurements in the Colorado River in Grand Canyon. J. Geophys. Res. Earth Surf. 125, e2019JF005226.

Rubin, D.M., Topping, D.J., Schmidt, J.C., Hazel, J.E., Kaplinski, M., Melis, T.S., 2002. Recent sediment studies refute Glen Canyon Dam hypothesis. EOS, Trans. Am. Geophys. Union 83, 273.

Sloff, K.C.J., Nieuwboer, B., Logan, B., Nelson, J.M., 2012. Effect of sediment entrainment and avalanching on modeling of Grand Canyon eddy bars, in: Murillo (Ed.), River Flow 2012. Taylor & Francis Group, pp. 791–798.

Sloff, K., Wright, S., Kaplinski, M., 2009. High resolution three dimensional modeling of river eddy sandbars, Grand Canyon, USA. River, Coast. Estuar. Morphodynamics RCEM 2009 883–890.

Topping, D.J., Wright, S.A., 2016. Long-term continuous acoustical suspended-sediment measurements in rivers—Theory, application, bias, and error. U.S. Geol. Surv. Prof. Pap. 1823 98 p.

Topping, D.J., Rubin, D.M., Vierra, L.E.J., 2000. Colorado River sediment transport 1.  Natural sediment supply limitation and the influence of Glen Canyon Dam. Water Resour. Res. 36, 515–542.

Topping, D.J., Rubin, D.M., Nelson, J.M., Kinzell, P.J.I.I.I., Corson, I.C., 2000. Colorado River sediment transport 2.  Systematic bed-elevation and grain-size effects of sand supply limitation. Water Resour. Res. 36, 543–570.

Wiele, S.M., Andrews, E.D., Griffin, E.R., 1999. The effect of sand concentration on depositional rate, magnitude, and location in the Colorado River below the Little Colorado River, in: Webb, R.H., Schmidt, J.C., Valdez, R.A., Marzolf, G.R. (Eds.), The Controlled Flood in Grand Canyon. American Geophysical Union, pp. 131–145.

Wiele, S.M., Griffin, E.R., 1997. Modifications to a one-dimensional model of unsteady flow in the Colorado River through the Grand Canyon, in: Water-Resouces Investigations Report 97-4046. U.S. Geological Survey, p. 7.

Wright, S.A., Topping, D.J., Rubin, D.M., Melis, T.S., 2010. An approach for modeling sediment budgets in supply-limited rivers. Water Resour. Res. 46, 1–18.

Wright, S.A., Schmidt, J.C., Melis, T.S., Topping, D.J., Rubin, D.M., 2008. Is there enough sand? Evaluating the fate of Grand Canyon sandbars. GSA Today 18.

Proposed Duty Station: Flagstaff, Arizona

Areas of PhD: Geology, hydrology, geophysics, engineering, physical science 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).

Qualifications:  Applicants must meet one of the following qualifications: Research Geologist, Research Geophysicist, Research Engineer, Research Hydrologist, or Research Physical Scientist.

(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.)

Human Resources Office Contact:  Audrey Tsujita, 916-278-9395,


Paul Grams, Ph.D.

Research Hydrologist
Southwest Biological Science Center
Phone: 928-556-7385

Jonathan Nelson

Research Hydrologist
USGS Water Resources Mission Area
Phone: 303-278-7957

Scott A Wright

Program Chief, Watersheds, Ecology, and Integrated Hydrologic Modeling (Acting)
California Water Science Center
Phone: 916-278-3024

David J Topping

Research Hydrologist
Southwest Biological Science Center
Phone: 928-556-7396

Erich Mueller

Southern Utah University