Abstract
The effect of vegetation recovery on water balance and sediment yield in mountainous region has been discussed for long time, however, the quantitative evaluation of the relation between vegetation recovery and runoff phenomena has not come to an end. In order to evaluate the effects of vegetation recovery, we have started observations of rainfall, discharge and sediment yield at 5 experimental basins located in the upper Watarase River. This paper describes a result of preliminary study concerned to the relationship between water stage and discharge of the sabo dam at which we installed water gauges. Sabo dams may be the most suited structures for measurement of water stages in these devastated upper mountain basins.
The results obtained are as follows. By the experiments, it was confirmed that the discharge from sabo dam is evaluated by Govinda-Rao's equation for broad crested weir in the range of 0.1<h/L, in which h is head and L is crest length. For the range of h/L<0.1, the characteristics of flow over crest becomes open channel type. But it was also confirmed by field observations that it is possible to use Govinda-Rao's equation instead of Mannning type equation for this h/L<0.1 range. If the depth of crest of prototype becomes smaller than 0.05m, then no equation can be used commonly for discharge estimation, and it is necessary to evaluate for each sabo dam.
