Abstract
In this study, it is a purpose to make clear the characteristics of the fish behavior to the increase and decrease of quantity flow (flow velocity). At the same time, it paid attention whether the pile dike used in the evacuation place of fish. Then, the model experiment carried out by using the compound cross-section open channel where the pile dike had been set up.
When flow velocity increased rapidly, the fish tried the evacuation behavior to the wall side and the pile dike. The fish that tried it in the pile dike that flow velocity is slow was able to stay in the place. Therefore, the fish used in the pile dike as the evacuation place. On the other hand, the fish that tried it to the wall side was swept away to the flow after the evacuation behavior. Moreover, the fish return run-up when flow velocity increased rapidly, too.
Reynolds stress (-pv`w`) increases when there are the pile dike on the flood channel, Reynolds stress (-pv`w`) increases and the secondary flow has developed. Therefore, the bank erosion and the river-bed scour are feared. In addition, it was suggested that the number of total individuals of fish that got on the flood channel increased, and the fish get left on the flood channel.
