Journal of the Japan Society of Erosion Control Engineering, Vol.59,No.4,2006
The surface runoff prediction model for the fine]tephra mantled slope
Takao YAMAKOSHI Katsuo SASAHARA Satoshi TAGATA Tetsuya ISHIDA Hidehiro TAKESHIMA
Eiichi WAKABAYASHI
Abstract
The surface runoff prediction model specified for the Hortonian overland flow
at the fine]tephra mantled slope is proposed in this study. Based on the numerical
solution of the Richard's equation, this model proposes the new surface boundary
condition that can describe the temporal change in an infiltration capacity. The
calculation to obtain the infiltration excess and the runoff hydrograph, which
is routined by the kinematic]wave method, is verified by the actual hydrographs
obtained by the hydraulic monitoring at the newly tephra]mantled slope in the
Miyakejima volcano, which erupted in July 2000 and deposited thick fine]grained
tephra on its slope. All the parameters of the unsaturated soil properties of
the deposited volcanic ash are obtained by the laboratory tests of the undisturbed
soil sample of the deposited volcanic ash. The verification shows that the result
of the calculation by the proposed prediction model shows good accordance with
the actual hydrographs though the proposed method has no controlling factor to
adjust to the actual hydrograph.
Key words:fine tephra, soil moisture characteristics, physical infiltration model,
Miyakejima volcano
Japan Society of Erosion Control Engineering
Sabo Kaikan Bekkan 3F, 2-7-5 Hirakawa-cho, Chiyoda-ku, Tokyo
Phone +81-3-3222-0747 Fax +81-3-3230-6759
http://www.jsece.or.jp/
Mail jimu@jsece.or.jp