31. Quantifying the effects of climate change and land-use on erosion rates using cosmogenic radionuclides and LiDAR-based process mapping

Climate change and land-use are altering pathways and supply rates of sediment moving through watersheds. As a result, hazards from floods and debris flows, and environmental degradation from excessive sediment loads, are causing increasing amounts of damage to infrastructure and ecosystems. Much of the damage is driven by changes in the geomorphic processes moving sediment through watersheds as landcover alters. For instance, loss of landcover in part of the Hawaiian Islands may have increased the occurrence of overland flow erosion, flooding reefs with damaging fine sediment. In Southern California, wildfires alter runoff processes, leading to debris flows that endanger lives and destroy property. Climate change may drive more frequent and devastating floods on desert alluvial fans, threatening infrastructure and communities. In each case, scientists will be asked what processes have changed in the watershed, and how much this change will alter quantity and character of the sediment load. Although methods for estimating the modern sediment load provide one part of the answer, another set of tools is required to assess transport processes and erosion rates in the recent and distant past, which then must be set in the context of past climate variability.

We seek a postdoctoral fellow who will combine cosmogenic radionuclide and other dating techniques with process mapping and geomorphic transport laws to quantify changes in sediment yield. We hypothesize that by using cosmogenic radionuclides (e.g., ²⁶Al, ¹⁰Be, ³⁶Cl, ³He, ¹⁴C) to estimate millennial and Holocene-timescale sediment budgets, historic supply rates from reservoirs, stream gages, or fallout radionuclides can be understood as a function of mapped process changes in watersheds. We hypothesize that process transitions (e.g., soil creep to overland flow) will change sediment yield and size relative to pre-disturbance rates by predictable amounts for given climate, geology and landcover. The goal of the science is to forecast approximate changes in sediment supply and size for scenarios of climate and landcover change. We anticipate that the research fellow will collaborate with existing USGS personnel engaged in vegetation and geomorphic process mapping, paleoclimate studies, tripod and airborne LiDAR acquisition, hydrology, and process studies of erosion in the steeplands of southern California, Hawaii or the arid Southwest.

Proposed Duty Station: Menlo Park, CA; Tucson, AZ

Areas of Ph.D.: Geomorphology, geochemistry, hydrology, geology

Qualifications: Applicants must meet one of the following qualifications: Research Geologist, Research Hydrologist, Research Geophysicist

(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.)

Research Advisor(s): Jonathan Stock, (650) 329-4968, jstock@usgs.gov; Kevin Schmidt, (650) 329-5302, kschmidt@usgs.gov; Dave Miller, (650)329-4923, dmiller@usgs.gov; Robert Finkel (Lawrence Livermore National Laboratory), (925) 422-2044, rfinkel@llnl.gov

Human Resources Office contact: Erica Settlemyer, (916) 278-9383, esettlemyer@usgs.gov

Summary of Opportunities