MONOLITHIC MODEL BETWEEN RIVER CHANNELS AND FLOOD PLAIN WITH QUAD-TREE GRID FOR HIGH REDUCING COMPUTATION COSTS

Abstract

Quad-tree grid system has two advantages: the grid system can express any geometry of plane forms in river and flood plane. Computation loads and number of grid can be decreased at the same time. This study derives truncation error of Quad-tree grid system for numerical stability, and number of grid of cross section in natural river for 2D computation based on rectangular grid. According to these results, a monolithic model between river channels and flood plain with Quad-tree grid system was developed and was applied to compute inundation of Shiotani river basin as in valley bottom plane. The numerical result can reproduce actual inundation area well and computation load was less than 30 percent comparison with computation employing fine grid for whole area.