Sarah Yarnell

Education Ph.D. in Hydrologic Sciences with an emphasis in Surface Hydrology and Stream Ecology, University of California, Davis, March 2005. M.S. in Geology with an emphasis in Fluvial Geomorphology, University of California, Davis, September 2000. B.S. with honors in Environmental Biology and Management and a minor in Geology, University of California, Davis, June 1995. Professional Background Sarah is an Associate Project Scientist at the Center for Watershed Sciences. Her studies focus on integrating the traditional fields of hydrology, ecology and geomorphology in the river environment. She is currently conducting research that applies understanding of river ecosystem processes to managed systems in the Sierra Nevada, with a focus on the development and maintenance of riverine habitat under current and future climate conditions. She is a recognized expert in the ecology of the Foothill yellow-legged frog (Rana boylii), a California species of special concern, and she is the first researcher to apply sediment transport and two-dimensional hydrodynamic modeling techniques to the evaluation of instream amphibian habitat. More recently, her experience has expanded to include consultation as a technical expert for various hydroelectric power relicensing projects (Big Creek Project, Desabla-Centerville Project, Middle Fork American Project, Yuba-Bear/Drum-Spaulding Project) and water management discussions (Inflows to the Bay-Delta), where she has worked closely with government resource agencies and the private sector to assess the impacts of environmental flows on aquatic biota. Research in Progress An experimental assessment of the mechanics of sediment transport during during flow events with varying hydrograph shape in labratory and natural field settings (in collaboration with University of Idaho, funded by National Science Foundation). An evaluation of water temperature regimes in high-elevation meadows in the Sierra Nevada with application to California and Little Kern Golden Trout in the Kern watershed (funded by US Forest Service). An experimental assessment of the impacts of flow recession dynamics on channel bar morphology and riparian vegetation (in collaboration with University of Idaho and US Forest Service, funded by National Center for Earth Surface Dynamics). Completed Projects An integrated analysis of empirical, hydrodynamic, and hydropower modeling data focused on improving the understanding and management of the spring snowmelt recession in Sierra Nevada rivers (in collaboration with US Forest Service, funded by California Energy Commission). Validation of regional habitat suitability criteria and instream flow modeling applications for the Foothill Yellow-Legged Frog (R. boylii) (in collaboration with US Forest Service, funded by California Energy Commission). Development of a conceptual model describing the ecological importance of the spring snowmelt recession in Mediterranean-montane environments (in collaboration with CWS researchers). Development and management of the amphibian study plan for the Placer County Water Agency Middle Fork American Hydropower relicensing project, included study plan development, field data collection, data analysis, and instream flow evaluation. Evaluation of aseasonal pulsed flow effects on R. boylii via integration of empirical, experimental and hydrodynamic modeling approaches (in collaboration with other R. boylii experts, funded by the Pulsed Flow Program at UC Davis and the California Energy Commission). Dissertation Research – Quantifying physical habitat heterogeneity: Concepts, methods, and ecological applicability with emphasis on R. boylii. Evaluation of sediment transport rates and processes in relation to aquatic habitat suitability in the Yuba River basin (in collaboration with USGS, Water Resources Division as part of the CALFED-funded Upper Yuba River Studies Program).