Prepared in cooperation with the Bureau of Land Management Landscape Evolution in Eastern Chuckwalla Valley, Riverside County, California Scientific Investigations Report 2021–5017 U.S. Department of the Interior U.S. Geological Survey Cover. U.S. Geological Survey photograph of wind-rippled sand and sand verbena in eastern Chuckwalla Valley, Riverside County, California. Landscape Evolution in Eastern Chuckwalla Valley, Riverside County, California By Amy E. East, Harrison J. Gray, Margaret Hiza Redsteer, and Matthew Ballmer Prepared in cooperation with the Bureau of Land Management Scientific Investigations Report 2021–5017 U.S. Department of the Interior U.S. Geological Survey U.S. Geological Survey, Reston, Virginia: 2021 For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment—visit https://www.usgs.gov or call 1–888–ASK–USGS (1–888–275–8747. For an overview of USGS information products, including maps, imagery, and publications, visit https://store.usgs.gov. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. Suggested citation: East, A.E., Gray, H.J., Redsteer, M.H., and Ballmer, M., 2021, Landscape evolution in eastern Chuckwalla Valley, Riverside County, California: U.S. Geological Survey Scientific Investigations Report 2021–5017, 46 p., https://doi.org/10.3133/sir20215017. Associated data for this publication: Gray, H.J., and East, A.E., 2021, Luminescence, weather, and grain-size data from eastern Chuckwalla Valley, Riverside County, California: U.S. Geological Survey data release, https://doi.org/10.5066/P9LZ02E4. ISSN 2328-0328 (online) iii Contents Abstract ...........................................................................................................................................................1 Introduction.....................................................................................................................................................1 Objectives...............................................................................................................................................3 Field Setting and Previous Work ........................................................................................................3 Methods...........................................................................................................................................................5 Weather Monitoring and Sand-Transport Modeling ......................................................................5 Surficial Sediment Characterization ..................................................................................................6 Stratigraphic Analysis and Luminescence Dating ..........................................................................7 Results .............................................................................................................................................................7 Weather and Sand-Transport Modeling ...........................................................................................7 Surficial Sediment Characterization ................................................................................................14 Stratigraphy and Luminescence Dating .........................................................................................27 Discussion .....................................................................................................................................................38 Conclusions...................................................................................................................................................40 Acknowledgments .......................................................................................................................................40 References Cited..........................................................................................................................................40 Figures 1. Maps of the study area in Chuckwalla Valley, eastern Riverside County, California ...........2 2. Photograph of a weather station deployed in eastern Chuckwalla Valley on February 7, 2019 .............................................................................................................................5 3. Graphs of wind speed and maximum gust speed for the study duration beginning on February 7, 2019, and ending December 21, 2020 ....................................................................8 4. Graphs of air temperature measured using the sensor mounted on the main weather-station and a sensor within the aluminum tipping-bucket rain gage ....................9 5. Graphs of relative humidity and cumulative rainfall during the study interval ................10 6. Polar plots of wind speed and wind direction for each month of 2019 .............................11 7. Polar plots of wind speed and wind direction for each month of 2020 .............................12 8. Histograms of 4-minute average wind-speed measurements for the entire study duration ..............................................................................................................................13 9. Photographs and polar plot showing evidence of a strong wind event October 30–31, 2019 ....................................................................................................................14 10. Graphs of wind speed, modeled sand flux, and cumulative modeled sand flux for the duration of the study ..................................................................................................................15 11. Wind-rose histogram of modeled sand flux showing frequency by direction .................16 12. Photographs of the land surface in polygon 1 and graph of grain-size for samples collected from polygon 1 in February 2019 .............................................................................17 13. Photographs of the land surface in polygon 2 and graph of grain-size for samples collected from polygon 2 in February 2019 .............................................................................18 14. Photographs of the land surface in polygon 3 and graph of grain-size for samples collected from polygon 3 in February 2019 .............................................................................20 15. Photographs of the land surface in polygon 4 and graph of grain-size for samples collected from polygon 4 in February 2019 .............................................................................21 iv 16. Photographs of the land surface in polygon 5 and graph of grain-size for samples collected from polygon 5 in February 2019 .............................................................................22 17. Photographs of the land surface in polygon 6 and graph of grain-size for samples collected from polygon 6 in February 2019 .............................................................................23 18. Photographs of the ephemeral stream channel Wiley Well wash, at the location immediately west of polygon 6, facing upstream, taken February 6, 2019 ........................24 19. Photographs of the land surface in polygon 7 and graph of grain-size for samples collected from polygon 7 in February 2019 .............................................................................25 20. Photographs of the land surface in polygon 8 and graph of grain-size for samples collected from polygon 8 in February 2019 .............................................................................26 21. Photographs of the land surface in the southeast side of the Palen dune field and graph of grain-size for samples collected from the southeastern part of the Palen dune field in February 2019 ................................................................................................................................28 22. Stratigraphic columns of five pits excavated in Chuckwalla Valley in March 2020 ........29 23. Stratigraphic column, photographs, and grain-size graph showing data collected from pit 1, excavated in March 2020 ................................................................................................... 30 24. Stratigraphic column, photographs, and grain-size graph showing data collected from pit 2, excavated in March 2020 ..................................................................................................32 25. Stratigraphic column, photographs, and grain-size graph showing data collected from pit 3, excavated in March 2020 ..................................................................................................34 26. Stratigraphic column, photographs, and grain-size graph showing data collected from pit 202, excavated in March 2020 ..............................................................................................36 27. Stratigraphic column, photographs, and grain-size graph showing data collected from pit 4, excavated in March 2020 ..................................................................................................37 Tables 1. Sediment-transport equations used to model aeolian sand flux ..........................................6 2. Vector sums of wind speed