Sediment detachment by rain power

被引:104
作者
Gabet, EJ [1 ]
Dunne, T
机构
[1] Univ Calif Santa Barbara, Dept Geol Sci, Santa Barbara, CA 93106 USA
[2] Univ Calif Santa Barbara, Donald Bren Sch Environm Sci & Management, Santa Barbara, CA 93106 USA
关键词
overland flow; rainsplash; sheetflow; grazing; washload; kinematic wave;
D O I
10.1029/2001WR000656
中图分类号
X [环境科学、安全科学];
学科分类号
08 ; 0830 ;
摘要
[1] In interrill areas, overland flow is often incapable of detaching soil particles so detachment is primarily by raindrop impact. We derive a mathematical expression, rain power (R,W m 2), relating the energy expenditure of raindrops impacting a soil surface to the rate of detachment of soil particles. Rain power incorporates rainfall, hillslope, and vegetation characteristics and is modulated by flow depths. Rainfall simulation experiments on natural hillslopes were performed to measure detachment rates and across-slope flow depth distributions in surface runoff. Our results indicate that flow depths follow a Poisson distribution, and this observation is used to develop a dimensionless function, A((h) over bar, d), that accounts for the interaction of flow depths (h) and raindrop diameter (d) in moderating detachment rates. Rain power correlates well with the detachment rate of fine-grained particles (psi, m(-2) s(-1)) so that psi = 0.011R(1.4) A((h) over bar, d) (n = 44, R-2 = 0.88, p < 0.005). We generalize this result to represent natural rainfall conditions and present a method for modeling sediment detachment rates and sediment discharge along entire lengths of hillslopes under the range of conditions where detached sediment is transported as wash load. Modeling simulations demonstrate the temporal and spatial variation in detachment rates caused by increases in flow depth.
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页数:12
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