Abstract
To elucidate the relationship between rainfall-runoff discharge and urbanization, the runoff models were established for each land use and the discharges from unit lots were analyzed in the Tedori River alluvial Fan Area where paddy field are dominant in land use. The area of lots, the shape and height of outlet and the percolation rate before and after mid-summer drainage in the paddy area, and infiltration capacity in no irrigation period of paddy, upland and residential area were investigated to establish the runoff models. The models correspond to five types of land use area, which included irrigated and non-irrigated paddy lots, upland field lots of barley and soy bean and a residential lot. The rainfall-runoff discharges from those lots were calculated for 54 storm events which ware corresponding to planning rainfall amount. The results indicated the followings; the maximum runoff ratio to total rainfall was calculated in the residential lot whereas minimum was in the irrigated paddy plot. The ratio in the irrigated paddy was remarkably increased with accumulated rainfall while those were not remarkable in other agricultural land use types. The peak runoff discharge was calculated by two types data, namely for one hour interval and ten minutes interval. In actual use of flood control planning the former peak discharge estimation method is convenient whereas the latter is theoretically reasonable except in the residential land.
