Decision-Support Tool for Constructing Robust Rainfall IDF Relations in Consideration of Model Uncertainty

Abstract

Intensity-duration-frequency (IDF) relations are essential for estimating extreme rainfalls for the design of various hydraulic structures. However, in current engineering practice, the construction of these relations represents a challenging and tedious task since it involves the uncertainty analysis of different probability models and the frequency analyses of a large amount of extreme rainfall data for different durations at a given site or over many different locations. In particular, the selection of the best probability model for extreme rainfalls is the most difficult decision since it requires two main challenging tasks: (1) a detailed evaluation of the descriptive and predictive abilities of each selected distribution as well as the analysis of its uncertainty and (2) a systematic comparison of the accuracy and robustness of all candidate models based on a number of graphical and numerical performance criteria. Hence, this paper proposes a decision-support tool, herein referred to as SMExRain, that can readily be used to identify, in an objective and systematic manner, the most suitable distributions for the accurate and robust estimation of design rainfalls. Therefore, SMExRain represents an efficient practical tool for establishing reliable IDF relations for a given site or for many sites of interest. The tool is based on the theoretical procedures developed by the authors and others. An illustrative application of SMExRain is presented using extreme data for the Ontario region (Canada) to demonstrate the efficiency and usefulness of the proposed tool in engineering practice.