Treatment of correlated storage drawdown and uncertainty in the flood hydrology for dams

Abstract

This paper addresses a number of issues arising from the application of MonteCarlo analysis to extreme flood estimation. There are a number of dams in Australia located within the catchment of another dam where storage volumes are correlated because of the way in which the system is operated. The Monte-Carlo analysis allows for inclusion of a probability distribution of storage volume, and correlation between two or more storages enabling interdependence between starting levels in two or more dams to be modelled. This approach addresses conservatism in estimates that are derived assuming both storages are full. The Monte-Carlo approach also allows us to characterise uncertainty in flood estimates resulting from the salient design inputs, namely the AEP of the PMP, and parameter uncertainty associated with the transfer function from runoff to flood hydrograph. The approach described here has been successfully applied to a number of dams.

Keywords:

• Monte-Carlo analysis
• extreme flood hydrology
• parameter uncertainty
• correlated storage drawdown

Additional information

Notes on contributors

L Mittiga

Lauren Mittiga is a flood hydrologist with four years experience working with Sinclair Knight Merz in hydrology and hydraulics. Lauren has experience with the development and calibration of rainfall runoff models, particularly RORB, and hydraulic modelling and inundation mapping downstream of large dams. She has been involved in extreme flood hydrology studies for approximately half a dozen dams located around Australia.

R Nathan

Dr Rory Nathan is the Principal Hydrologist with Sinclair Knight Merz. He holds degrees in different aspects of engineering hydrology from the Universities of Melbourne and London. He has over 25 years experience in academic and consulting positions, both here and overseas. Rory’s technical interests are in engineering and environmental hydrology, modelling of hydrological processes, and the analysis of hydrological extremes. He is an Honorary Fellow at the University of Melbourne and at Monash University, and maintains an active research interest in the eWater CRC. He has published over 100 papers in refereed journals and conference proceedings, and has won several national and international awards for his research. In 2000, Rory was named the national Civil Engineer of the Year by the Institution of Engineers Australia.

P Hill

Peter Hill has more than 15 years experience in flood hydrology, water resource and dam safety risk assessment. After completing a Master of Engineering Science on extreme flood estimation, he worked as Project Leader within the Cooperative Research Centre for Catchment Hydrology. Since joining Sinclair Knight Merz in 1996, he has worked on a wide range of hydrology projects across Australia. He has authored or co-authored more than 40 technical papers and is a member of Engineers Australia’s National Committee for Water Engineering.

E Weinmann

Erwin Weinmann spent the first part of his professional career in the Victorian water industry, where he attained the position of Principal Hydrologist with the Rural Water Commission/Corporation. Since 1993, he has been associated with the Department of Civil Engineering at Monash University and with the CRC for Catchment Hydrology; he is now an Honorary Associate of the Department. Erwin’s main research and consulting interests are in flood estimation and flood management, water resource assessment and water supply system modelling. He is part of the team involved in the current revision of Australian Rainfall and Runoff.