The aim of this paper is to indicate how to utilize the storage and adjustive control of the natural topography of valleys in the construction of dams and to determine their scales more effectively. The function of sediment control by means of a bottle-neck valley and a sabo dam is studied through experiments. Both constriction and sabo dams give rise to hydraulic jump and there is a strong linear positive relativity between the length of the jumps and sediment volume on each slope. Through the experiments, the authours clarified that sediment can be controlled better if the contraction ratio is larger. If topographical characteristics, such as the constriction below an expansion part, can be utilized, even a smallscale dam it has a strong ability to control sediments.
The deformation (response) and the rupture limit of steel beams struck by boulders inside a debrisflow are made clear for the design of slit dams using steel pipes, as a measure against debris flows. Static loading tests and impact bending rupture tests on simple beams and cantilevers have been conductedto find out the characteristics of deformation. The measured values can be well explained by applyingthe 2-mass system model. The impact force absorptivity is to be used as a criterion (EDC) for the impactbending rupture. It can be obtained by equating it to the static energy absorptivity, with the followingempirical formulae. For simple beams, EDC=0. 57Zp2/I+6. 30(tf·cm) For cantilevers, EDC=2. 75 Zp2/I-1. 00(tf·cm) where, EDC is the impact force absorptivity(tf·cm) Zp is the coefficient of plastic section(cm3) and I isthe geometrical moment of inertia(cm4) .