HR: 17:15h
AN: U24A-06    [Abstracts]
TI: Chronotopographic Analysis To Detect Small, Seasonal Hillslope Change Based On Point Cloud Data, Black Mesa Escarpment, NE Arizona
AU: * Wawrzyniec, T F
EM: tfw@unm.edu
AF: University of New Mexico, Dept. of Earth and Planetary Sciences, Albuquerque, NM 87131, United States
AU: Frechette, J D
EM: jdfrech@unm.edu
AF: University of New Mexico, Dept. of Earth and Planetary Sciences, Albuquerque, NM 87131, United States
AB: TLS techniques have been introduced to an on-going investigations of semiarid landscapes, we are attempting to document the seasonal change related to hillslope processes that lead to pulses of erosion and sedimentation associated with weakly cemented sandstones along part of the Black Mesa escarpment of NE Arizona. Dendrochronology coupled with soil geomorphic analysis indicates that abundant sediment is being shed from weathered slopes at vertical denudation rates of 2-3 mm/year over 10-100 yr timescales, causing rapid localized valley floor aggradation. Employing the UNM LiDAR Laboratory Optech Ilris 3D terrestrial LiDAR scanner, we have devised a method for chronotopographic analysis where subsequent point-cloud data sets are compared directly to each other. Focusing on a single small (30x60m) area of a mostly non-vegetated, steep slope (>35°), we demonstrate that the devised method of comparative analysis of point cloud data sets can detect sub-centimeter change resulting from a single season of monsoon precipitation along the escarpment. Using repeat scans spanning the 2006 and 2007 monsoons has provided an empirical evaluation of single season erosion rates for the study site that ranges between 5-20mm/yr. Thi anomalously high value is consistent with previously work that suggests that large amounts of change occur during large rain events that follow periods of prolonged drought. The 2006 monsoon followed a well documented 7 year period of severe drought conditions and set regional records for summer rainfall throughout much of the southwest. This data set should also document the parts of the slopes that make the greatest contribution to local valley floor aggradation. In demonstrating the utility of this method, we expect that continued investigation of this site will provide insight to the key processes associated with soil- mantled vs. bedrock-dominated slopes during modern escarpment retreat and hillslope modification. Such insights may then elucidate the impacts of Holocene climate change on this rapidly evolving landscape.
DE: 1625 Geomorphology and weathering (0790, 1824, 1825, 1826, 1886)
DE: 1826 Geomorphology: hillslope (1625)
DE: 5415 Erosion and weathering
DE: 9350 North America
SC: Union [U]
MN: 2007 Fall Meeting