Development of New Inter-Event Time Definition Technique in Urban Areas

Abstract

Rainfall in rainy seasons continuously occurs and it is hard to separate individual events which is a significant source for the design of drainage facility to reduce Combined Sewer Overflows (CSOs). The current design of drainage facilities is based on the maximum design for rainfall events despite its extensive use in urban areas. The design of drainage facility requires the characteristics of rainfall such as average annual rainfall volume, duration and intensity. The individual rainfall events in a continuous rainfall event can be divided by Inter-event Time Definition (IETD). Current techniques for the determination of IETD are autocorrelation analysis, the coefficient of variation analysis, and average annual number of rainfall events analysis. The problem of the existing three methods for IETD is an ambiguous result for the decision. The new method for the determination of IETD using exponential function is suggested. The probability density function of the continuous rainfall event is compared with the confidence range of regression curve generated from the exponential functions at each inter-event time. The comparison of current and new method for the determination of IETD is conducted in the target watershed.