Author(s): TAKAO TAMURA, Yasunori Muto, Mahito Kamada, Mahito Kamada

Linked Author(s): TAKAO TAMURA, Yasunori Muto, Mahito Kamada, Mahito Kamada

Keywords: Forest basin; Flood reduction function; Runoff analysis; Surface runoff;

Abstract: Mountain region forest is important as the water source area in a river basin. A forest basin has the flood reduction function which achieves reduction in flood peak flow and delay in peak time. General recognition is that the water-holding ability of the forest soil takes charge of important role of the function. When considering the flood disaster which occurs in the downstream, it's necessary to estimate the feature of surface runoff flow which shows on the ground. Because the surface runoff flow accounts for the most part of flood flow and its velocity is very fast compared with other runoff flow in the ground. So the flood reduction evaluation index was proposed by this research. The index combines the water-holding ability of the forested soil and the difficulty in floating down the surface runoff flow. In seven forest basins, runoff analysis and flood simulation were applied. Those vegetation and geological feature have many varieties. A relation between the forest characteristic (ground roughness, slope length and the angle of the slope) and flood reduction function was considered using runoff model parameters. As a result, the importance of ground roughness was suggested. When using the proposed evaluation index, it's possible to get quantitative evaluation of flood reduced function in a forest and the information to improve the function efficiently.

DOI: https://doi.org/10.3850/38WC092019-1474

Year: 2019