水田地帯の機械排水計画における流出解析の精度について

In paddy field area, generally, a runoff hydrograph under rainstorm tends to have the characteristics giving extremely smooth shape and long period of runoff because of storage and flood. Therefore, a unit time and a basic rainfall to be used for runoff analysis of pumping drainage should be decided after general consideration based on these characteristics.
To clarify the runoff mechanism above mentioned, some investigations were carried out in paddy field area of Anba river near Lake Shinji, Shimane Prefecture. Results of them are as follows :
i ) The reasonable unit time for runoff analysis is about 6 hours.
ii ) Three-day storm should be used as the basic rainfall.
Though the results in this paper were obtained by only one example, runoff characteristics everywhere in paddy field area in our country show a similar tendency, so that the results will give a clue to the practical treatment for the runoff analysis which is applied to pumping drainage.