EXPERIMENTAL STUDY ON THE EFFECT OF ANISOTROPY OF POROSITY IN A CALCULATION GRID ON A FLOOD INUNDATION PATTERN

To enhance the soft-countermeasure on increasing heavy rain and disaster, research on increasing the accuracy of two-dimensional (2D) flood inundation model is necessary. The objective of this study is to grasp the effect of anisotropy of porosity in calculation grid on a flood inundation pattern by comparing a hydraulic model experiment with numerical simulations by a 2D flood inundation model wich includes an isotropic porosity in each grid. In experiments, anisotropy was represented by changing the aspect ratio of large roughness elements mounted on a plain. Large velocity differences was observed for the propagation speed of floods in the experiments on the floodplain model with the shape of the roughness elements. Numerical simulation results demonstrated that the difference could be represented by changing the drag coefficient, however, the tip of the inundation current, and the reflection or shielding effect by the elements could not. The needs are clearly shown to develop the anisotropy effect in the numerical model.