- Title
- Assessment of the impacts of rating curve uncertainty on at-site flood frequency analysis: a case study for New South Wales, Australia
- Creator
- Rahman, Ataur; Haque, Md Mahmudul; Haddad, Khaled; Rahman, Ayesha S.; Kuczera, George; Weinmann, Erwin
- Relation
- Hydrology and Water Resources Symposium 2014. Proceedings of the Hydrology and Water Resources Symposium 2014 (Perth, W.A. 24-27 February, 2014) p. 962-969
- Relation
- http://www.engineersaustralia.org.au/
- Publisher
- Engineers Australia
- Resource Type
- conference paper
- Date
- 2014
- Description
- The flood data reported by gauging authorities, though perceived as measured data, is rather estimated from a rating curve. The rating curve represents a relationship at a particular gauged location between water level and flow values. The lower part of the rating curve is generally established based on flow measurements during smaller flood events typically up to an annual exceedance probability (AEP) of 1 in 10; however, the rating curve usually needs extrapolation to flood magnitudes corresponding to AEPs of 1 in 100 and beyond. There are different methods of rating curve extrapolation, with different degrees of uncertainty associated with them. Most hydrologic models use at-site flood data as “accurate” measured values in evaluating the model performance, thus creating a misconception in hydrologic practice. This paper examines the rating curve uncertainty levels for a set of New South Wales (NSW) catchments, which have been assembled as a part of Australian Rainfall and Runoff (ARR) Project 5 ‘Regional Flood Methods’. ARR-FLIKE is used to assess the impacts of rating curve uncertainty on at-site flood quantile estimates. 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 AEP 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. The findings of this study are based on 96 NSW catchments only, and hence caution should be applied in drawing inferences for other catchments and/or other parts of Australia. Further study with a greater number of catchments from all Australian states should be undertaken to understand better the impacts of rating curve extrapolation uncertainty on flood frequency analysis results in different situations.
- Subject
- rating curve; floods; flood frequency analysis; ARR; FLIKE
- Identifier
- http://hdl.handle.net/1959.13/1065407
- Identifier
- uon:17831
- Identifier
- ISBN:9781922107190
- Language
- eng
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