Abstract
Debris flow occures and causes serious damages, losses of human lives in paticular somewhere in Japan almost every year. Wall type sabo dams or check dams have been adopted to prevent debris flow disasters. Though, their functions have not been made clear quantitatively. Some experiments were carried out to evaluate the functions of sabo dams abainst debris flow. Results are as follows;
(1) A sabo dam reduces the peak sediment concentration, makes the time of peak discharge behind and flatten sediment discharge. These functions are expected more as the capacity of dam is larger.
(2) Coarse grains concentrated at the front of debris flow can be trapPed by a sabo dam.
(3) Even if a sabo dam has been filled with sediment, it is effective to some extent.
(4) The gradient of deposition changes as tlme passes. Depositional surface once rises up to the gradient parallel to the channel gradient when a debris flow reaches there, then drops because the supplied sediment is limited and the sediment concentration decreases gradually.
(5) If the gradient below a dam is steeper than 15 degrees, the water squeezed out from the debris flow deposited at the sabo dam could generate another debris flow below the dam.
