HR: 0800h
AN: H21B-0509    [Abstracts]
TI: Estimating 3D Variation in Active-Layer Thickness Beneath Arctic Streams Using Ground- Penetrating Radar
AU: * Brosten, T R
EM: troybrosten@mail.boisestate.edu
AF: Department of Geosciences, Boise State University, 1910 University Drive, Boise, ID 83725, United States
AU: Bradford, J H
EM: johnb@cgiss.boisestate.edu
AF: Department of Geosciences, Boise State University, 1910 University Drive, Boise, ID 83725, United States
AU: McNamara, J P
EM: jmcnamar@boisestate.edu
AF: Department of Geosciences, Boise State University, 1910 University Drive, Boise, ID 83725, United States
AU: Zarnetske, J P
EM: zarnetsj@geo.oregonstate.edu
AF: Department of Geosciences, Oregon State University, 104 Wilkinson Hall, Corvallis, OR 97331, United States
AU: Gooseff, M N
EM: mgooseff@engr.psu.edu
AF: Civil & Environmental Engineering Department, Pennsylvania State University, 212 Sackett Bldg., University Park, PA 16802, United States
AU: Bowden, W B
EM: breck.bowden@uvm.edu
AF: Rubenstein School of the Environment and Natural Resources, University of Vermont, 304 Aiken Center, Burlington, VT 05401, United States
AU: Johnston, M J
EM: mjohnsto@uvm.edu
AF: Rubenstein School of the Environment and Natural Resources, University of Vermont, 304 Aiken Center, Burlington, VT 05401, United States
AB: Our earlier ground-penetrating radar (GPR) investigations beneath arctic streams revealed greater active layer thicknesses beneath stream channels than beneath the adjacent terrestrial tundra. Presented here are results from 3D GPR data sets which were gathered over three sites to measure the active layer thickness variation within local streambed morphology. Three sites were selected based on their geomorphic differences. The first site is a high-energy water flow reach with a cobble to gravel streambed lining and riffle-pool morphology (alluvial stream). The second site is a deeply incised low-energy water flow reach with a beaded morphology and organic streambed lining (peat stream). The last site features a beaded morphology but with alluvial material lining the pool areas. GPR data were acquired using a pulsed radar system with a high-powered 1000V transmitter. The transmitting and receiving 200 MHz antennas were placed at the bottom of a small rubber boat for data acquisition. Profiles were gathered by pulling the boat across the stream from bank-to-bank while triggering at a constant time interval. Lines were collected at ~30cm intervals and continued upstream until a riffle-pool sequence was covered. Precise spatial data were collected using DGPS in conjunction with the GPR data. In addition, temperature data were recorded using thermocouples placed at varying substream depths located within or near the study sites to aid and verify GPR interpretations and numerical heat flow models. Results from the alluvial stream site illustrates greater thaw depths beneath riffle and gravel bar features compared to the neighboring pool areas while the beaded stream sites indicate the opposite, greater thaw depths beneath pools and thinner thaws beneath the connecting runs.
DE: 0706 Active layer
DE: 0798 Modeling
DE: 1830 Groundwater/surface water interaction
DE: 1835 Hydrogeophysics
SC: Hydrology [H]
MN: 2007 Fall Meeting