When we discuss the effect of debris flow control structures or when predict debris flow prone areas, it is necessary to predict debris flow hydrographs. Many data of debris flow hydrographs have not been collected so far. At Hunshui Gully in China intensive observation was carried out in the late 1970's. These data are analyzed. Some characteristics of debris flow hydrographs have been made clear; runoff rate, the coefficient of peak discharge and the relationship between sediment discharge and water discharge. A rainfall-runoff model was applied to explain debris folw hydrographs. Most debris flow hydrographs can be explained by the method. Debris flows of large peak discharge, however, can not be explained. It is considered that some natural dams appeared dne to landslides and collapsed in those cases from comparing observed and calculated hydrographs.

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This study presents an experimental approach to investigate the effect of rubber for the impact resistant design of the steel pipe structures.
The static loading tests and dropping weight impact tests have been performed for steel pipe beam wrapped with rubber and filled with rubber, respectively.
(1) It is found from the dropping weight impact tests that the kinetic energy of the dropping weight has been about 10-30% absorbed by the rubber in the case of the steel pipe wrapped with rubber.
(2) On the other hand, the brittle fracture observed in the steel pipe beam filled with concrete has not been observed in the case of steel pipe beam filled with rubber. It has been confirmed that the steel pipe beam filled with rubber can absorb the large capacity of kinetic energy by the large deformation capacity.

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Originally Japanese Erosion Control Technologies (SABO) were designed for disaster prevention and landuse development. However, as general public concerns are widened from disaster prevention to protection of riparian environment in Japan, SABO works have received increasing criticism. We should recognize a coming new era in which SABO cannot be used in hazardous areas for the single purpose of erosion control without also protecting ecological values. The objective of this paper is to present new technical ideas to improve riparian environment as part of SABO. Four hierarchical spatial scales of consideration are proposed as a framework for managing riparian environment; two of these scales (landscape and channel unit) were not considered in old SABO planning. Each value, such as disaster prevention, maintenance of ecological dynamics, and habitat improvement, occurs at a distinctive scale in this hierarchical structure. The author believes a hierarchical concept is very helpful to arrange multi-values into a coherent structure of management for riparian environment.

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Steel-slit dams are often used to trap debris flow. It is expected to be effective to trap bed load. Therefore, in order to study the latter function, a hydraulic experiment of the steel-slit dam was held. As the result, it is revealed that the steel-slit dam for trapping bed load is effective if the ratio of grain size to slit length is nearly 1, and that the function of the steel-slit dam is described by non-dimensional tractive force.

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