Journal of the Japan Society of Erosion Control Engineering, Vol.60,No.4,2007

Distributed runoff model for fine‐tephra mantled mountain basin

Satoshi TAGATA, Takao YAMAKOSHI, Jun'ichi KURIHARA, Katsuo SASAHARA, Masaaki SAKURABA, Shu TAKAHASHI and Masaru ONODERA

Abstract

In this study, a distributed runoff model based on the surface runoff prediction model using the numerical solution of Richard's equation, the surface runoff model and saturated flow using the kinematic‐wave method, and the unsteady flow model using the dynamic‐wave method was proposed. This model allows calculations to be made for different infiltration characteristics in the study basin.
The digital elevation model consisted of nonstructural grids, and the hydrographic basin was divided into slope divisions and channels in this runoff model.
The calculation to obtain the runoff hydrograph was verified by actual hydrographs obtained by hydraulic monitoring at the newly tephra‐mantled basin in Miyakejima volcano, which erupted in July 2000 and deposited thick fine‐grained tephra. All the parameters of the soil properties of the deposited volcanic ash were obtained by laboratory and field tests.
The verification shows that the calculation results by this distributed runoff model show good accordance with the actual hydrograph.

Key words：fine tephra, distributed hydrological model, Hortonian surface flow, Miyakejima volcano

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