Streamflow data Preparation for Regional Flood Frequency Analysis: Lessons from Southeast Australia

Abstract

This paper presents a case study on streamflow data preparation for a regional flood frequency analysis (RFFA) project for the states of Victoria and NSW, in connection with the forthcoming edition of Australian Rainfall and Runoff. The study gathered annual maximum flood series data for a large number of stations from Victoria and NSW, and applied various statistical techniques to prepare the final data set. It was found that a large primary data set, even if selected using a fairly stringent set of criteria, cannot guarantee a similarly large final data set, as streamflow data are affected by many sources of uncertainty. The trade-offs between quality and quantity are discussed and illustrated. The maximum rating ratio, defined as the ratio of the largest estimated flow and the maximum measured flow at a gauging station, is used to identify stations whose quantiles may be seriously affected by rating curve errors. In a case study involving Victorian stations, the importance of maintaining a high spatial coverage of stations was demonstrated. It was shown that a 50% reduction in the number of stations used in a RFFA resulted in an increase of the standard error of prediction of flood quantiles up to 90%.

Key Words:

• Regional floods
• design floods
• floods
• flood data

Additional information

Notes on contributors

K Haddad

Khaled Haddad is undertaking his PhD research at the University of Western Sydney (UWS). He obtained his BEng (Honours) and MEng (Honours) in Hydrology from UWS. His research is focused on regional flood frequency analysis, with a particular emphasis on uncertainty in regional flood models and the regional modelling of large to rare floods. Prior to starting his PhD, Khaled was a floodplain management engineer with Liverpool City Council, working on many different flood mitigation and water resources projects, which included revisions to Council’s stormwater and wetlands asset management plans. Khaled is also involved in the current revision of Book 4 in the Australian Rainfall and Runoff series.

A Rahman

Dr Ataur Rahman is a Senior Lecturer in Water and Environmental Engineering in the School of Engineering, University of Western Sydney, Australia. He has over 18 years experiences in water industries, research, and universities in Australia and southeast Asia. He obtained his BScEng degree from Khulna University of Engineering and Technology in Bangladesh, MSc (Hydrology) degree from National University of Ireland Galway, and PhD degree in Hydrology from Monash University in Australia. His research interests include flood hydrology, urban hydrology and environmental risk assessment. He received the G. N. Alexander Medal from Engineers Australia in 2002. He has published over 100 research papers in water and environmental engineering field. He is acting as Project 5 Leader (Regional flood methods in Australia) in the forthcoming revised version of Australian Rainfall and Runoff.

P E Weinmann

Erwin Weinmann is currently a Research Associate of the Department of Civil Engineering, Monash University. He holds a Diploma in Agricultural Engineering and Surveying from the Swiss Federal Institute of Technology in Zurich, and a MEngSc from Monash University. His professional career spans over 40 years, including a number of roles in the Victorian water industry, teaching and research at Monash University, and professional consulting. His main interests are in flood estimation, flood risk management, and water resource assessment and management. As a Project Leader with the CRC for Catchment Hydrology, Erwin contributed to the development of a number of improvements in flood estimation methodology and practice. He is a corresponding member of Engineers Australia’s National Committee on Water Engineering, and heavily involved in the current revision of Australian Rainfall and Runoff.

G Kuczera

George Kuczera is Professor of Water Engineering in the School of Engineering at the University of Newcastle. He obtained his PhD from Harvard University in 1980 and spent 5 years in the water industry before joining the University of Newcastle in 1986. His research interests cover a range of areas including Bayesian calibration and testing of hydrologic models, stochastic hydrology and risk assessment, water resource systems analysis, and multi-criteria optimisation. He has published extensively on these topics and has developed a range of software for use in research, education and industry. George has been recipient of the G. N. Alexander and Warren Medals from the Engineers Australia, and has served as Chairman of the National Committee on Water Engineering.

J Ball

James E Ball is an Associate Professor in the School of Civil and Environmental Engineering at the University of Technology Sydney (UTS). His primary research interest is in the development and application of catchment modelling systems, particularly in urban environments. This includes the determination of parameters for these systems and the use of information technology in the determination of these parameters. As part of his research activities, he is heavily involved with monitoring of surface water resources in field situations and the usage of this information in modelling environments. Prior to joining UTS, James obtained experience as a consulting engineer and in a government authority. He is a past member (currently a corresponding member) of the IAHR and IWA Joint Committee on Urban Drainage, a member of the IAHR - IAHS - IWA Committee on Hydroinformatics, and a co-opted member of Engineers Australia’s National Committee on Water Engineering. He is a member of the editorial boards for the Urban Water Journal and the Journal of Hydroinformatics, and an Editor for Water Science and Technology. He has been appointed by Engineers Australia as the Technical Editor responsible for the current revision to Australian Rainfall and Runoff.