A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering

Thesis (M.Eng.) - Asian Institute of Technology, 1989

The most important work that a drainage designer has to deal with is the analysis of rainfall frequency. It is necessary to develop a computer aided system to make this complex and difficult work smooth. In the. present study, an attempt was made to develop a software package, namely UDDS (Urban Drainage Design System) that can perform all of the analysis: parameter estimation, goodness of fit test, and the magnitude and variance estimation of T-year event. Through the decision criteria, a best fitting distribution can be selected. Once the distribution model has been confirmed, the related design specification can be established. This UDDS package consists programs dealing with five distribution models, namely LN3 (Three-parameter lognormal distribution), LN2 (Two- parameter lognormal distribution), LLG (Log-Logistic distribution), GEV (Generalized extreme value distribution) and EV1 (Extreme value type-1 distribution) and various parameter estimation methods for each model. Chi-square and Kolmogorov-Smirnov tests and Jackknife technique are important for evaluation which are also included in this package. The rainfall data of three typical stations: Taipei, Taichung and Kaohsiung located in the North, Central and South of Taiwan respectively were picked up for investigation. From the analysis results, the best fitting distribution was recommended for the three stations. The LLG with PWM2 method was selected for Taipei and Taichung stations and the LN3 with Stedinger's method was recommended for the Kaohsiung station.