Revision of design rainfalls over Australia: A pilot study

Abstract

Design rainfalls for standard durations from 24 hours up to 72 hours are derived using all readily available up-to-date rainfall data for an area in southeastern Queensland/northeastern New South Wales. Based on the annual maximum rainfall series, L-moments are derived at each site for a set of standard durations. A “region of influence” approach is employed to produce regionalised estimates of design rainfall. The network of continuously recording rain gauges is much less dense than the network of daily rain gauges. Data at longer durations is used to infer statistics at the shorter durations. For durations between 1 and 12 hours, a Partial Least Squares Regression model is developed to infer L-CV and L-skewness from the independent variables: L-CV and L-skewness at 24 hours, latitude, and distance from the coast. This procedure utilises information at the 24 hour duration to increase data coverage at the shorter durations. Maps of design rainfalls for standard average recurrence intervals from 1 to 100 years, and standard durations are produced using a combination of meteorological experience and a thin-plate smoothing spline algorithm. Results are compared with design rainfalls published in Institution of Engineers Australia (1987).