HR: 08:45h
AN: H51L-04    [Abstracts]
TI: Comparison of Terrestrial LiDAR and Erosion Pin Networks for Bank Geometry Monitoring
AU: * Frechette, J D
EM: jdfrech@unm.edu
AF: Earth & Planetary Sciences, MSC03 2040, 1 University of New Mexico, Albuquerque, NM 87131, United States
AU: Wawrzyniec, T F
EM: tfw@unm.edu
AF: Earth & Planetary Sciences, MSC03 2040, 1 University of New Mexico, Albuquerque, NM 87131, United States
AU: Stormont, J
EM: jcstorm@unm.edu
AF: Civil Engineering, MSC01 1070, 1 University of New Mexico, Albuquerque, NM 87131, United States
AU: Coonrod, J
EM: jcoonrod@unm.edu
AF: Civil Engineering, MSC01 1070, 1 University of New Mexico, Albuquerque, NM 87131, United States
AB: Erosion pins and repeat surveys are valuable tools for measuring geomorphic change where airborne remote sensing platforms do not provide the required accuracy or are impractical. Recent advances in automated systems, e.g. the Photo-Electronic Erosion Pin system, permit the collection of high temporal resolution data, however, these systems do not address the inherently low spatial resolution of erosion pin networks and high spatial resolution digital terrain models (DTM) are time consuming to produce with standard surveying equipment. In contrast, Terrestrial LiDAR systems (TLS) enable the rapid generation of DTMs that routinely contain several thousand data points per m² without disturbing the target area. We describe the use of TLS to monitor changes in bank geometry along an 800 m reach of the Rio Grande in Albuquerque, NM with comparison to data from an erosion pin network along the same reach. On 31 July 2006, shortly after the inception of our monitoring campaign, a thunderstorm produced flows out of the Calabacillas Arroyo that deposited over 10,000 m³ of sediment into the main stem of the Rio Grande within the study area. These deposits reduced the width of the Rio Grande by half and buried nearly all of the erosion pins downstream of the arroyo. Rio Grande and Calabacillas flows continued to rework these deposits since that time. This sediment pulse exceeded the measurement capacity of the erosion pin network and it only registered a large event, followed along part of the reach by a return to near pre-event conditions months latter. In contrast, the cm scale pre- and post-event DTMs produced by TLS document local changes in geometry and enable volumetric estimates of sediment gain and loss. These are minimum estimates, however, as the DTMs only include sediments exposed by low flows at the time of the scans. Furthermore, as with all resurvey techniques, the temporal resolution of the TLS time series is limited by the frequency with which the site could be reoccupied. Although additional work is needed these preliminary results demonstrate the utility of TLS for documenting geomorphic change with cm scale accuracy, in particular episodic large-magnitude events that may preclude direct measurement.
DE: 1817 Extreme events
DE: 1821 Floods
DE: 1825 Geomorphology: fluvial (1625)
DE: 1855 Remote sensing (1640)
DE: 1895 Instruments and techniques: monitoring
SC: Hydrology [H]
MN: 2007 Fall Meeting