A STUDY ON THE FORMATIVE PROCESS OF FLOOD HYDROGRAPH IN A RIVER BASIN

In the previous paper, we concluded that flood hydrographa from the whole river basin(4. 4 k㎡) can be calculated directly using hydrographs from the smaller sub-basin (0. 18k㎡) included in it, under the following assumptions1) The flood hydrographa from sub-basins which are same order as the specified sub-basin, are equal in runoff duration and proportional to their drainage areas in runoff intensity.2) The stream channels in the whole river basin are characterized by so-called linearchannel.This paper describes the application of these assumptions to the estimation of floodhydrographa in larger river basin of the River Chikugo being 537 kmi in area. It is shownthat the flood hydrographa at any location in the river basin can be estimated accuratelywhen the suitable specified sub-basin is selected, the proper propagation speed of floodflow is evaluated, and the movement of rainy area and the spacial distribution of amountof rain are taken account of.