Estimating Peak Runoff for Risk-Based Assessment in Small Catchments

Abstract

SummaryThe management and design of hydraulic infrastructure requires detailed analysis of the rainfall-runoff process, as well as the allocation of an acceptable level of risk. Risk-based assessment of the rainfall-runoff process requires methodologies that are both accurate and efficient. Although the Rational Method has been a popular analysis tool in risk based assessment, it has many short comings requiring significant subjective judgement by the engineer. Rainfallrunoff models have become increasingly popular in this regard, as they provide accurate tools to predict the deterministic processes taking place in the catchment. A methodology is presented in this paper for incorporating rainfall-runoff models in risk-based assessment that is both efficient in terms of computational effort and accurate. The method relies on the adoption of a storm pattern that embodies the characteristics contained within the statistically based rainfall data that is generally adopted in practice. The methodology has been tested on two hypothetical catchments and 47 small gauged catchments in Queensland. It is shown that using this methodology, statistically based peak runoff can be predicted at all locations in the catchment where suitable catchment subdivision had been undertaken.