HR: 1340h
AN: H53C-1393    [Abstracts]
TI: The effect of slope angle on splash detachment in steep forest plantation
AU: * Mizugaki, S
EM: gakimizujp@yahoo.co.jp
AF: Japan Science and Technology Agency, 705 Sogo-Kenkyuto-A, Univ. Tsukuba, 1-1-1 Ten- nodai, Tsukuba, 305-8572, Japan
AU: * Mizugaki, S
EM: gakimizujp@yahoo.co.jp
AF: Graduate School of Life and Environmental Sciences, University of Tsukuba, 503 Sogo- Kenkyuto-A, Univ. Tsukuba, 1-1-1 Ten-nodai, Tsukuba, 305-8572, Japan
AU: Nanko, K
EM: knanko@geoenv.tsukuba.ac.jp
AF: Graduate School of Life and Environmental Sciences, University of Tsukuba, 503 Sogo- Kenkyuto-A, Univ. Tsukuba, 1-1-1 Ten-nodai, Tsukuba, 305-8572, Japan
AU: Onda, Y
EM: onda@geoenv.tsukuba.ac.jp
AF: Graduate School of Life and Environmental Sciences, University of Tsukuba, 503 Sogo- Kenkyuto-A, Univ. Tsukuba, 1-1-1 Ten-nodai, Tsukuba, 305-8572, Japan
AB: To study splash detachment rate and investigate the effects of rainfall and slope angle on splash detachment, the field observation of splash detachment was conducted for five months using 27 splash cups under natural rainfall events in Japanese cypress (Hinoki; Chamaecyparis obtusa) plantation in the Shimanto River watershed, southern Japan. In this plantation forest, the unit kinetic energy of throughfall (unit KE; J/m²/mm) was found to be constant independent of rainfall intensity. The total rainfall over six observation periods was 853 mm and the maximum rainfall intensity for 1 h ( RI_1h) varied from 8.0 to 19.6 mm h^-1. A significantly high coefficient of linear regression was found between RI_1h and the average splash detachment of all splash cups over six periods, although the splash detachment from the individual cups had larger variations with RI_1h. This variation in splash detachment may attribute to the spatial variability in soil surface condition such as slope angle. In the relationship between the splash detachment and slope angle, no correlation was found over the entire periods. However, different correlations were found among the observation periods due to the differences in rainfall intensity. The splash detachment from a lower slope angle (14°) exhibited a strong relation with the maximum rainfall intensity for a shorter period, such as 10 to 30 minutes. In contrast, the splash detachment from a slope angle of over 35° exhibited high correlation with the maximum rainfall intensity for 3 h, suggesting that longer time is required for ponding in steeper slopes than gentler slopes. In gentler slopes, prolonged rainfall may cause the higher ponding depth, resulting in reducing the raindrop impact and less splash detachment. Therefore, under the forest canopies, the effect of slope angle on the rainfall parameter should be incorporated into the future splash erosion model.
DE: 1815 Erosion
DE: 1826 Geomorphology: hillslope (1625)
DE: 1862 Sediment transport (4558)
DE: 1865 Soils (0486)
SC: Hydrology [H]
MN: 2007 Fall Meeting