Abstract
River discharge is one of the fundamental data in flood frequency analysis. Accuracy of these discharge data is crucial as uncertainty in these data is directly translated into flood quantile estimates which have significant impact in flood risk assessment and engineering design. Generally, these discharge data reported by the gauging authorities are not measured directly, rather estimated through a rating curve which represents a state-discharge relationship at a particular river section. Consequently, this causes uncertainties in the discharge data as the true rating curve is unknown and the established rating curves are generally most likely to be associated with some degrees of errors due to several factors. Despite the fact that rating curve uncertainty can introduce errors in discharge data, it is often disregarded in the flood frequency analysis. This paper examines the impacts of rating curve uncertainty on flood quantiles estimates for a set of New South Wales catchments in Australia, which have been assembled as a part of Australian Rainfall and Runoff Project 5 ‘Regional Flood Methods’. The results indicate that a higher assumed value of rating curve uncertainty in flood frequency analysis inflates the uncertainty bounds of the estimated flood quantiles (i.e. increases the width of the 90% confidence limits). This is more noticeable for smaller annual exceedance probability floods. Based on results from the 96 catchments examined here, it has been found that the difference in flood quantile estimates for different assumed rating curve uncertainty values do not depend on standard deviation and skew of log-space annual maximum flood series data. It is noted that the rating curve uncertainty issue needs to be recognised in flood frequency analysis as this represents a significant source of uncertainty in flood frequency analysis, which is often ignored in practice.
Original language | English |
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Pages (from-to) | 50-58 |
Number of pages | 9 |
Journal | Journal of Hydrology and Environment Research |
Volume | 2 |
Issue number | 1 |
Publication status | Published - 2014 |
Keywords
- flood forecasting
- floods