ABSTRACT
Physical and dynamic characteristics below bed surface can be an important parameter to discuss the physical environment characteristics of habitats for aquatic fauna and flora. In this research, the spatial distribution of the bed strength, the porosity of the bed and the sediment size distribution of bed material are studied on the bar located in the Kizu River in Kyoto, Japan by use of the field survey and the numerical analysis. The results show that the porosity is varied from 0.4 to 0.17 on the bar. This result shows that the constant porosity value (0.4) which is used by the most bed deformation analysis is large for the bed degradation area. Furthermore, the first hit penetration value is larger as the porosity is larger and the linear relationship is found between them. However, the first hit penetration value becomes very small under the condition which the porosity is smaller than 0.22. The porosity along the main flow which is calculated by two dimensional model is large, because the sediment size becomes finer and standard deviation of the sediment diameter becomes smaller. On the other hand, the porosity on the bar is smaller because the standard deviation of the sediment diameter is larger. The porosity varies under the condition that the standard deviation of the sediment diameter is large. Hence, it is considered that the calculated porosity on the bar is the minimum porosity and can be found after the compression.
