Development of a new regional flood frequency analysis method for semi-arid and arid regions of Australia

![CDATA[The limited availability of streamflow data at both temporal and spatial scales in the semi-arid and arid regions of Australia makes it difficult to develop statistically meaningful regional flood frequency analysis (RFFA) methods. As a part of Australian Rainfall and Runoff (ARR) revision Project 5 Regional Flood Methods, a simple RFFA method is developed here for the semi-aroid and arid regions. This RFFA method has generally a lower degree of accuracy (with median relative error in the range of 55% to 71%) than the RFFA method developed for the non-arid data-rich regions of Australia (with median relative error typically in the range of 30% to 45%). The RFFA method presented here for the semi-arid and arid regions should be used with caution; local hydrological knowledge should be used to interpret the results and wherever possible, the results should be compared with other methods, such as rainfall runoff models and locally available methods. It is recommended that some representative stream gauges be established in the semi-arid/arid regions for ‘long-term monitoring’ to develop a comprehensive database which will assist in upgrading the RFFA methods in the semi-arid and arid regions in future. An application tool is being developed which will facilitate the application of the ARR RFFA method for both the semi-arid/arid and humid/coastal regions with minimum input from the user. The RFFA method presented here needs to be recalibrated with the new intensity-frequency-duration data, which will be available soon as a part of ARR Revision Project 1.]]