HR: 1340h
AN: G13B-0806    [Abstracts]
TI: Distinguishing process through form in alluvial fans, eastern Death Valley, California
AU: * Volker, H X
EM: hvolker@memphis.edu
AF: Department of Earth Sciences, University of Memphis Johnson Hall, Memphis, TN 38152 United States
AU: Ellis, M A
EM: mellis@memphis.edu
AF: CERI, University of Memphis, Memphis, TN 38152 United States
AU: Wasklewicz, T A
EM: twsklwcz@memphis.edu
AF: Department of Earth Sciences, University of Memphis Johnson Hall, Memphis, TN 38152 United States
AB: We use high resolution (1m) ALSM data to assess the morphology as a function of length-scale of alluvial fan form in Eastern Death Valley, California. The goal of the study was to develop topographic fingerprints that would enable formative processes to be distinguished from form alone. Thus, alluvial fans were divided into two categories based on field observations of the sedimentological features and apparent formative processes: Clast Rich, predominately debris flow (CR), and Mixed Flow, largely a mixture of debris flow and fluvial processes (MF). The data used in the study were collected and post-processed into a bare-earth model by personnel from the National Center for Airborne Laser Mapping (NCALM). Gridded DEMs of the bare-earth data were generated in ESRI's ArcInfo, from which individual alluvial fans were delineated via 1 m hillshade and curvature grids. DEMs of individual fans were detrended by removing a second-order polynomial surface from the original fan surface. The detrended fan surface revealed topography at relatively short length-scales and removed the dominant longitudinal slope trend that would wash-out the local-relief signature. We examined local-relief as a function of length-scale and used this parameter to determine if statistical differences in form occurred between the CR and MF fans. We find three distinct topographic fingerprints that enable CR fans to be distinguished from MF fans. 1. For any length-scale, local-relief is higher in CR fans than in MF fans; 2. MF fans show a more pronounced positive skewness of local-relief than do CR fans; and 3.The average slope, measured at a length-scale of 1 m, separates CR from MF fans . These fingerprints would be unavailable from a standard 10 m or 30 m DEM. The values reflect differences in surface variability due to varying structures (debris flow lobes, channel, interfluves, etc.) on the fans. Very high-resolution DEM data has the potential to fulfill the long-standing goal that process may be tractable from form. These fingerprints should be useful to modelers because they provide a benchmark to evaluate the success of physical and numerical models.
DE: 8040 Remote sensing
DE: 8107 Continental neotectonics
DE: 1824 Geomorphology (1625)
DE: 1294 Instruments and techniques
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting