土砂供給で変動する河床の石礫の露出高を予測する方法の提案

抄録

The exposed height of river-bed materials decreases when sediment supplied from upstream is deposited. The estimation of the exposed height should contribute to evaluate the effects of sediment supply on the habitat of attached algae and fish. Hence, we developed a new model to estimate the average height of exposed stones and their distribution. In the new model, mixed particle sizes on the river bed were classified on the basis of their sizes, and it was assumed that the vertical positions of materials in the same class had a normal distribution. In addition, the measured data on exposed height at downstream of a dam was gathered for comparing the results of model.

The average heights calculated by the model were from 80 to 90 mm, similar to the measured heights. The distributions of calculated heights showed good agreement with the measured heights, when the measured data had a normal distribution. The model showed that the exposed height in fine river-bed materials decreased easily than that of the height in coarse river-bed materials, and that the height in river-bed materials of equal sizes decreased easily than that in river-bed materials of different sizes.