Abstract
This study mainly deals with the characteristics of suspended sediment running off from a forest road surface. According to the existing experience model relating to the suspended sediment run off, the amount of the suspended sediment is, at second power, proportional to its run off amount but turned out not to be so practically. Therefore, the experience model is not desirable. By recalculating the conventional opened data, this study shows that the relations between the amount of suspended sediment and its flowing amount can simply be expressed by a linear model. It is also found that the amount of easy-to-flow out increases at a rate of one power of the residual amount on road surface. In this regard, if the run off rate of suspended sediment is inversely proportional to its residual amount, the characteristics of its flow are experimentally examined. The result is that the running off rate of suspended sediment depends upon rainfall intensity and longitudinal slope. More specifically, the running off rate of suspended sediment is proportional to rainfall intensity and increases at a rate of two power of longitudinal slope.
