This paper presents the results of the investigations on several runoff characteristics of the low lying district near Lake Shinji, Shimane Prefecture. Usually the unit hydrograph method based on several assumption is yet an excellent mean for analysis of the runoff in spite of its deficiency for consideration that runoff process is essentially non-linear phenomena. The authors have tried to apply the unit hydrograph method to the case of this low lying paddy field with classification of the unit hydrograph corresponding to variation of rainfall amount, below 50mm, 50mm～100mm, above 100mm and got to the following conclusion that :
The classified unit hydrographs on the basin concerned are to a certain extent applicable to calculation of the runoff analysis for rainfall corresponded, especially in small rainfall this tendency is evident. If it is possible to presume how the unit hydrograph available at present transform according to change of the flow condition by cannal improvement, the unit hydrograph method stays in position of the most useful step for runoff analysis.