J. Jpn. Soc. Soil Phys. No. +**, p.+/,0,**/ * Application of Soil Physics to Rainwater Dynamics at Forested Hillslopes Ken ichirou KOSUGI* * Graduate School of Agriculture, Kyoto University, Kyoto 0*02/*,, Japan Abstract Rainwater dynamics at forested hillslopes are one of the most important themes in forest hydrology, because they have large e#ects on storm and base flow hydrographs, occurrences of slope failures, material transports in forest ecosystem, and stream water chemistry. Rainwater infiltration and discharge processes at forested hillslopes can be e#ectively studied by using methodologies developed in soil physical studies, which includes methods for determining saturated-unsaturated soil hydraulic properties, equipments for measuring matric potential and water content in field soils, and numerical simulation techniques for saturated-unsaturated soil water flow. This paper introduces several previous and new studies which applied the methodologies of soil physics to the analyses of rainwater dynamics at forested hillslopes. Topics includes characteristics of forest soil hydraulic properties in comparison with disturbed sandy and loamy soils, e#ects of pore structure of forest soil on rainwater infiltration, indices of water holding capacity of forest soils, e#ects of soil water-repellency on heterogeneous infiltration and occurrence of surface runo#, experiments and modeling of soil-pipe flow, as well as rainwater infiltration in weathered bedrock. Key words : forest hydrology, forest soil, water retention characteristic, hydraulic conductivity, pipe flow + CO,,,+ + 0*1* cm,** mmh * 0*02/*, :
16 +**,**/ Brooks and Corey, +30. ; van Genuchten, +32* ; +32, Kosugi, +330 ; Chan and Govindaraju,,**- y r Young Laplace yar + A y r cm *.+/ cm,,* Kutílek and Nielsen, +33. lnr Kosugi, +33., +330 S e qqr Q lnyy m q sq r s / mm +** cm -.0*.- g, /.0+ cm,,,/ cm,.* + 0*1* cm +** + +33,,, Richards q C y K y C dq dy exp lnyym,,s, KK s S e +, Q lnyy m s s, S e : K s : q s : y* q q r : y q Q Qx exp u,, du x Excel QxNORMSDISTx y m S e*./ y m r m s lnr
: 17, y m s y m r m, Kosugi +331 a r m s heavy clay sandy loam -, qy Ky K s y m s Kosugi, +331 b y /* cm q -a y * y K - b,-, - +/* cm./., mm - a b +333
18 +**,**/. a b, c d 2* cm.b, c Richards. b, c *.*+. c 2. d. c +/+2 2,-. d *.*+. b +3. d 3. b - 2,,.2,
: 19 / S +333. d,.. - a qy C y +** cm C - b y,* cm K q y Ky +32, +32/ +333 S p q out p q out S S p q outp q q z y q outp / q outp y / a
20 +**,**/ y yz K yp / a, b y * / b Ky q y / c, +, yz / a / c y z q q outp yy * / a q y * q / c +, S + S +, S, y L L y * q + y q S C dq dy S / df qy K y, - K. K s p / e Kp y -. / e y -y. y - / d y - S. / f S -S. K S S K C 0. S p +/* cm - qy, Ky S...0 mmh S 0*/ mmh 0 S. 0 -+ S +333 -, Richards 1 Sentek EasyAG-/P / cm 1/ cm +* cm. 1 a 1 b. b, c +/ +3 mm +/+2 1/ cm // cm - * +* cm *.0,*.00,,*** mmh
: 21 1 a b 1 b Noguchi et al., +333 ; +333 +321 1 3* +333 -,, 2 +, m -,***.,*** ha A *, cm.* + m,, m 2 a +32 mm 2*
22 +**,**/ +33/ +,+-*,,+-* mmh A * / cm,,2.*-,-1* mmh A * 2 b /2 NDST ninety degree surface tension / / cm +/./ cm 1 3 +33/ +/ 1.- cm +* cm, 1* cm + cm, *.2 cm, -* cm *./ cm - s +* a No pipe Open pipe +/ cm Closed pipe No pipe Kosugi et al.,**. +* a..+ Darcy 3 Uchida et al., +333
: 23 +* a b Kosugi et al.,**. Open pipe Closed pipe ++ a b Kosugi et al.,,**. +* Closed pipe *.+2 cms *.*,,- cms +* b Closed pipe ++ a ++ b Tsutsumi et al.,**/
24 +**,**/ +, a b c Darcy-Buckingham.,,**. :,**. +, a +, b N c +* cm /* +330 +- TDR +, c TDR k +-,
: 25 - TDR +2 mm, +- k - cm k k k +- JSTCREST / Richards Kosugi et al.,,**+ +, c Katsura et al.,,**/ +33+ Richards Fick Brooks, R.H. and Corey, A.T. (+30.): Hydraulic properties of porous media. Hydrol. Pap. no. -. Colorado State Univ., Ft. Collins. Chan, T.P. and Govindaraju, R.S. (,**-): A new model for soil hydraulic properties based on a stochastic conceptualization of porous media. Water Resour. Res., -3 : ++3/, doi : +*.+*,3 /,**, WR **+3/.. +33+ :.. :,--*. Katsura, S, Kosugi, K., Yamamoto, N. and Mizuyama, T. (,**/): Saturated and unsaturated hydraulic conductivities and water-retention characteristics of weathered granitic bedrock +333 : --/ : -/.,. Kosugi, K. (+33.): Three-parameter lognormal distribution model for soil water retention. Water Resour. Res., -* : 23+3*+. Kosugi, K. (+330): Lognormal distribution model for unsaturated soil hydraulic properties. Water Resour. Res., -, :,031,1*-. Kosugi, K. (+331 a): A new model to analyze water retention characteristics of forest soils based on soil pore radius distribution. J. For. Res.,, : +2. Kosugi, K. (+331 b): New diagrams to evaluate soil
26 +**,**/ pore radius distribution and saturated hydraulic conductivity of forest soil. J. For. Res.,, : 3/+*+. +333 : 2+ :,,0,-/.,**. :. /1 - : 1+13. Kosugi, K., Mori, K. and Yasuda, H. (,**+) : An inverse modeling approach for the characterization of unsaturated water flow in an organic forest floor. J. Hydrol.,,.0 : 30+*2. Kosugi, K., Uchida, T. and Mizuyama, T. (,**.) : Numerical calculation of soil pipe flow and its e#ect on water dynamics in a slope. Hydrol. Process., +2 : 111123. Kutílek, M. and Nielsen, D.R. (+33.) : Soil hydrology. p. /-, Catena Verlag, Cremlingen, Germany. Noguchi, S., Tsuboyama, Y., Sidle, R. C. and Hosoda, I. (+333) : Morphological characteristics of macropores and the distribution of preferential flow pathways in a forested slope segment. Soil Sci. Soc. Am. J., 0- : +.+-+.,-. +321 : 03 : -0,-01. +330 : pp. +/,- +32, : 0. :.*3.+2. +32/ : 01 :..3.0*. +33, : p. -1 Tsutsumi, D., Sidle, R.C. and Kosugi, K. (,**/) :A simple model of lateral preferential flow in hillslope soils.,**. : - /1, : /2 0.. Uchida, T., Kosugi, K. and Mizuyama, T. (+333) : Runo# characteristics of pipeflow and e#ects of pipeflow on rainfall-runo# phenomena in a mountainous watershed. J. Hydrol.,,,, : +2-0. +33/ : +*0 : /*//*2. van Genuchten, M. Th. (+32*) : Aclosed-form equation for predicting the hydraulic conductivity of unsaturated soils. Soil Sci. Soc. Am. J.,.. : 23, 232. +33/ : 11 :,,.,-+. :,**/. +2 :,**/ / +3