Research Opportunity Description
Throughout the geologic history of Earth and other planetary bodies, transgressions and regressions of water levels (stages) in oceans, lakes, and river channels have influenced sediment transport in adjacent aeolian landforms. Transgressions inundate or saturate sediment, for example on beaches and coastal aeolian dunes, and cause aeolian sediment transport to be supply-limited either through direct inundation of sediment or because the moisture increases inter-particle bonding and sediment cohesion, making sediment less mobile. Regressions cause sediment deposits to dry, leading to transport-limited conditions where aeolian sediment transport is limited by wind velocity instead of by the supply of dry sediment. Thus, alternating periods of transgression and regression provide opportunities to examine scenarios of, and transitions between, the endmember conditions of zero sediment supply (i.e., supply-limited) and essentially unlimited sediment supply where aeolian transport is instead limited by wind velocity (i.e., transport-limited). The effect of water stage changes on aeolian sediment transport is important for understanding how fluvial and aeolian processes interact, particularly considering their connection to internally drained lake basins or reservoirs with river inflows or outflows effected by climatic variability and human land use. For example, dewatering of freshwater basins owing to drought or human consumptive water use can reduce fluvial discharges of water, potentially leading to exposed river channels and lake beds becoming source areas for aeolian sand transport and atmospheric dust.
We seek proposals to develop and implement novel model workflows to predict the aeolian erosion, transport, or deposition of sand or dust from subaerially exposed river- or reservoir-sourced sediment deposits as a function of changing water supply, use, and regulation. Proposals should focus on the Lake Powell or Lake Mead reservoirs, or the segment of the Colorado River flowing through Grand Canyon which is regulated by the upstream Glen Canyon Dam impounding Lake Powell. By focusing on this region, proposals can leverage some of the most extensive and highest-resolution hydrology, remote sensing, geomorphology and riparian ecology datasets for any reservoir or river corridor in the world (see Grand Canyon Monitoring and Research Center, River Ecosystems Science and Lake Powell Research).
Along the Colorado River in Grand Canyon National Park, windblown river sand provides important wildlife habitat, sandy areas for camping, and a protective cover for archeological sites. However, the extent of bare sand has decreased since construction of the upstream Glen Canyon Dam, which traps sediment in Lake Powell. Along the shorelines of Lake Powell in Glen Canyon National Recreation Area and Lake Mead in the Lake Mead National Recreation Area, beaches provide recreational areas for boaters, campers, and off-road vehicle enthusiasts, but are also a potentially increasing source area for windblown dust as more areas are exposed subaerially as reservoir levels fall in response to climate change, drought, water use, regulation and policy considerations. Proposed modelling can build from previous research in these environments that has examined, for examples: river regulation by dams and aeolian landscapes (Draut, 2012), role of drying on the aeolian transport of river-sourced sand (Sankey et al., 2022), river flooding and sand supply for aeolian dune landscapes (Sankey et al., 2018), past and future river hydrology and sediment availability for aeolian transport (Kasprak et al., 2021). Proposed modelling should provide practical insight into: (i) how reservoir water storage might be managed to minimize shoreline dust emissions relative to other water and resource considerations, or (ii) how river flows might be managed to maintain sandy river valley landscapes and dunefields. However, the proposed work can also provide theoretical insight into the response of aeolian processes to sediment supply changes driven by periods of anthropogenic activity, drought, and climate change. There is wide latitude in this opportunity to propose novel modelling that is physically-based and leverages numerical, geospatial, remote sensing, field measurement, statistical, computer science, and/or informatics approaches.
Interested applicants are strongly encouraged to contact the Research Advisor(s) early in the application process to discuss project ideas.
References:
Draut, A.E., 2012. Effects of river regulation on aeolian landscapes, Colorado River, southwestern USA. Journal of Geophysical Research: Earth Surface, 117(F2).
Kasprak, A., Sankey, J.B. and Butterfield, B.J., 2021. Future regulated flows of the Colorado River in Grand Canyon foretell decreased areal extent of sediment and increases in riparian vegetation. Environmental Research Letters, 16(1), p.014029.
Sankey, J.B., Caster, J., Kasprak, A. and Fairley, H.C., 2022. The Influence of Drying on the Aeolian Transport of River‐Sourced Sand. Journal of Geophysical Research: Earth Surface, 127(12), p.e2022JF006816.
Sankey, J.B., Caster, J., Kasprak, A. and East, A.E., 2018. The response of source-bordering aeolian dunefields to sediment-supply changes 2: controlled floods of the Colorado River in Grand Canyon, Arizona, USA. Aeolian research, 32, pp.154-169.
Proposed Duty Station(s)
Flagstaff, Arizona
Areas of PhD
Geology, geography, hydrology, ecology, informatics, 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 Geographer, Research Computer Scientist, Research Hydrologist, Research Physical Scientist, Research Statistician
(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.)
