Jinzu Sabo Construction Office has been studying triggering, transport and deposition mechanism of debris flows at Shiramizu-dani creek of Mt. Yakedake (Jinzugawa river system) since 1977. In order to obtain accurate data safely, a remote control automatic recording system has been employed. It is considered that Crib type Sabo dam is one of the most effective Sabo dams to control debris flows. Observations as to the effective of Crib dam (Shiramizu dani No. 2 Sabo dam) against debris flows have been carring out since 1983. This paper shows the outline of observation systems and data on the impact force of debris flows, the movement of debris flows inside and outside the Crib dam, etc. We will continue these observations to produce the basic data for constructing new type Sabo bams.