The effect of small rainfall events in the urban runoff production

Keywords Abstract In urban catchment because of developed conditions, the amount of impervious area increases which tends to increase peak discharge rate and runoff volume. Knowing the importance of rainfall volume helps to appropriate design of storm water control facility. In this article analytical model was applied for investigation the importance of small rainfall events in runoff production. Therefore; rainfall events less than 8 mm was considered as small rainfall events. The test catchment was located in upper part of District No. 22 of Tehran. There was no existing rainfall gauge in the test catchment, long term rainfall series was taken from Mehrabad rainfall station and the data from 1959 to 1998 were used. The results of