昭和57年長崎豪雨における中島川の洪水氾濫解析

Abstract

The Nakashima River which runs through midle of Nagasaki City has overflowed its banksowing to the heavy rainfall of more than 400mm per 7 hours from 17:00 to 24:00 in July 23, 1982.In this paper, based on the fact-finding survey, river characteristics related to the bed slopes, river width and capable discharge were examined, and the flooding processes, inundated area andthe distribution of its water depth were reported.To simulate this flood event, a simple runoff analysis was carried out at first, then usinghydrographs obtained by this analysis as input data, unsteady two dimensional overland floodflow in Nakashima basin was analyzed by the numerical simulation method. Calculated resultsconcerning to the water depth and the flow direction showed relatively good agreement withobserved ones. The effect of the tide level was also investigated.