302-4 Fusion of ground-penetrating radar and terrestrial lidar to investigate fluvial-aeolian interactions within a dam-regulated river valley

Session: Aeolian Systems in Time and Space (Posters)

Poster Booth No.: 157

Presenting Author:

Joshua Caster

Authors:

Caster, Joshua¹, Kelley, Madeline M.², Sankey, Joel B.³, Porter, Ryan C.⁴, East, Amy E.⁵, Bransky, Nathaniel⁶, Kasprak, Alan⁷, Fairley, Helen⁸

(1) U.S. Geological Survey, Southwest Biological Science Center, Grand Canyon Monitoring and Research Center, Flagstaff, AZ, USA, (2) U.S. Geological Survey, Southwest Biological Science Center, Grand Canyon Monitoring and Research Center, Flagstaff, AZ, USA, (3) U.S. Geological Survey, Southwest Biological Science Center, Grand Canyon Monitoring and Research Center, Flagstaff, AZ, USA, (4) Northern Arizona University, School of Earth and Sustainability, Flagstaff, AZ, USA, (5) US Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA, USA, (6) U.S. Geological Survey, Southwest Biological Science Center, Grand Canyon Monitoring and Research Center, Flagstaff, AZ, USA; Northern Arizona University, School of Informatics, Computing, and Cyber Systems, Flagstaff, AZ, USA, (7) Oregon State University, College of Earth, Ocean, and Atmospheric Sciences, Corvallis, OR, USA, (8) U.S. Geological Survey, Southwest Biological Science Center, Grand Canyon Monitoring and Research Center, Flagstaff, AZ, USA,

Abstract:

The interaction between rivers and adjacent aeolian dunes are an important mechanism of landscape evolution across Earth and other planets. Evidence for these fluvial-aeolian interactions can be preserved in the sedimentary record, ranging from single events to multi-year conditions, representing the influence of climate, geomorphic, and biophysical conditions. However, the interface between fluvial shorelines and adjacent aeolian dunes is dynamic, with the potential to rework and obscure sedimentary structures and bedforms. This overprinting of geomorphic processes presents challenges to investigating the interplay between flood deposits and the volume of wind-reworked sediment migrating over them.  In this study, we combine almost a decade of terrestrial lidar surveys (TLS), collected along the fluvial-aeolian interface, with ground-penetrating radar (GPR), collected as 2-dimensional survey profiles, to investigate recent aeolian activity within, and adjacent-to, sites with known flood disturbance and deposition. This novel approach allows detailed comparisons of measured annual sedimentary surface changes to observed stratigraphic expressions of fluvial and aeolian deposition and sediment transport. We focus analysis on two select river-sourced dunefields from Grand Canyon National Park in the southwestern USA, both sourced from sandbar sediment deposited by dam-regulated floods. We use these data to 1) assess the relationship between previously mapped lidar topography and observed patterns in radar reflectivity below the recent sedimentary surface and 2) infer preserved evidence of geomorphic interactions during or preceding the past six decades of river regulations. We observe several strong radar reflectors within the upper meter of the survey profiles that correspond with lidar surface measurements in the preceding years. The highest amplitude reflectors are associated with older flood deposits periodically exposed by dune blowouts while lower amplitude arrivals are associated with stoss and lee slopes of migrating dunes. Later arriving GPR returns, associated with deeper reflectors (> 2 m), appear to show similar characteristic patterns in reflectivity, with high amplitude features paralleling known flood surfaces, low amplitude features tilted parallel to recent dune slopes, and all of which occur above a zone of parabolic distortion believed to be the basal debris fan.  Broadly, the results demonstrate that complex geomorphic interactions might be discernable along the fluvial-aeolian interface, and that combining TLS and GPR is useful for interpreting how these interactions are shaping the past and present landscape.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8939

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