洪水比流量曲線へのアプローチ

Abstract

It may be usefull to know the magnitude of the peak discharge of a record flood from a givendrainage area for the safety design of spillway of a dam and/or for the planning of precautionarymeasure for flood disasters in a river basin with different drainage area of the same hydrologicalcharacteristics and under the similar meteorological conditions. Unfortunately, however, thephysical or statistical characteristics of the regional maxima of flood peak has not hitherto beenstudied enough to sevre for the engineering practice in Japan.A study has been carried out from the point of view that the peak discharge of flood from ariver basin is the synthetic reflection of both characteristics of rainfall concentration in time andspace and of runoff of the basin. The basins of the River Obata in Kinki district, the River Tozuin Kii-Nanbu district and the River Ibi in Chubu district have been chosen in order to investigatethe DAD characteristics of heavy rainfalls. The equation of the peak discharge of flood from agiven drainage area has been obtained by combining the equations of DAD and the time of floodconcentration and drawn in a figure of log q (m3/sec/km2) to log A (km2). Such a curve has thenbeen slid to the log q direction to envelop flood peaks in the same district rivers. Every envelop-ing curve has shown good fitness far better than the Creager's curve.Finally, the parameters in the equation of enveloping curve have been examined and adjustedto set a common form of the equation in every district in Japan. The curves from the author'sequation show good fitness to record flood peaks in every district in Japan. They would be usedin Japan instead of the Creager's curves.