ANALYSIS OF THE RELATIONSHIP BETWEEN SURFICIAL GEOLOGY AND PARAMETER IN RAINFALL RUNOFF MODELS AND ITS APPLICABILITY TO LARGE-SCALE FLOODS

Abstract

 This paper analyzes the relationship between the parameters and the surficial geology that greatly affects the runoff in mountainous watersheds in 32 dam watersheds consisting of a single geology to elucidate the physical characteristics for improving the accuracy of rainfall-runoff models. In addition, the applicability of the rainfall-runoff model to large-scale floods was examined by simulating an unprecedented large-scale flood in a dam basin with different surficial geology. The results show that the relationship between surficial geology and parameters is dominated by parameters related to intermediate runoff, and that the variation of parameters is larger in granitic and volcanic rocks. As for the applicability of the model to large-scale floods, the results of parameter estimation by large-scale floods, regardless of the surficial geology, were found to represent the peak flow rate the best, indicating the applicability of the model to large-scale floods.