HR: 1340h
AN: H43G-1700    [Abstracts]
TI: Estimation of suspended sediment sources using Cs-137 and Pb210ex in unmanaged Japanese cypress plantation watersheds of southern Japan
AU: * Onda, Y
EM: onda@geoenv.tsukuba.acjp
AF: School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tenno-dai, Tsukuba, 3058572, Japan
AU: Mizugaki, S
EM: gakimizu@geoenv.tsukuba.ac.jp
AF: School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tenno-dai, Tsukuba, 3058572, Japan
AU: Mizugaki, S
EM: gakimizu@geoenv.tsukuba.ac.jp
AF: Japan Science and Technology Agency, 1-1-1 Tenno-dai, Tsukuba, 3058572, Japan
AU: Fukuyama, T
EM: t-fukuyama23@yahoo.co.jp
AF: National Institute for Agro-Environmental Sciences, Japan, 3-1-3 Kannon-dai, Tsukuba, 3058604, Japan
AU: Koga, S
EM: satoko_k_1031@t.vodafone.ne.jp
AF: Graduate School of Environmental Sciences, University of Tsukuba, 1-1-1 Tenno-dai, Tsukuba, 3008572, Japan
AU: Asai, H
EM: asmt001@yahoo.co.jp
AF: Graduate School of Environmental Sciences, University of Tsukuba, 1-1-1 Tenno-dai, Tsukuba, 3008572, Japan
AU: Hiramatsu, S
EM: shira@shinshu-u.ac.jp
AF: Department of Forest Science, Faculty of Agriculture, Shinshu University, MInami-minowa 8304, Kamiina, 3994598, Japan
AB: To assess the suspended sediment sources in unmanaged Japanese cypress plantation watersheds, field measurements and fingerprinting of suspended sediment were conducted in the Shimanto River basin, southern Japan. For the fingerprinting, Cs-137 and Pb210ex were detected by gamma-ray spectrometry for the potential source materials in the surface soil of the forest floor, the stream bank and the truck trail, the mobilized sediment by raindrop impact and overland flow, and the suspended sediment in the stream channel. The Cs-137 and Pb210ex activities associated with forest floor materials were considerably higher than those of the stream bank and truck trail. The Cs-137 and Pb210ex activities associated with suspended sediment were found to vary with the sampling period. These results suggest that the suspended sediment can comprise materials from forest floor and/or landslide scar and that from truck trail and/or stream bank. The generally lower contribution from the forest floor in Hinoki 156 as compared to that from Hinoki 155 indicates that truck trail networks may be secondary sources of suspended sediment in unmanaged Japanese cypress plantations. Based on field measurements, overland flow occurred during rainfall events on the hillslope, eroded the surface soil on the forest floor, and transported sediment downslope. Overland flow on the truck trail networks may also transport forest floor sediment into the stream channel. These results indicate that the forest floor should be recognized as an important source of fluvial sediment in this watershed.
DE: 1815 Erosion
DE: 1826 Geomorphology: hillslope (1625)
DE: 1850 Overland flow
DE: 1851 Plant ecology (0476)
DE: 1862 Sediment transport (4558)
SC: Hydrology [H]
MN: 2007 Fall Meeting