Sydney Catchment Authority and Infrastructure NSW


Dam, Monte Carlo, Hydrology, hydraulics


The NSW government wishes to investigate flood behaviour in the Hawkesbury Nepean and mitigation options to reduce flood risk to large downstream population centres in Sydney.


We developed our own in house Monte Carlo environment which allows the robust stress testing of options against 1000’s of events which represent observed flood behaviour. The Monte Carlo model reproduced variability in rainfall, spatial patterns, temporal patterns, losses, and timing of tributaries. Over 10,000 events were run through both a hydrologic and hydraulic model. Instead of just have a handful of design events based on one set of design inputs this resulted in a 1000’s of different flood events which represent the observed variability in flood behaviour.

The model results were used as inputs to other components of the study including:

  • Damages assessment
  • Evacuation modelling
  • Evacuation planning
  • Upstream ecological impacts
  • Training events for SES personnel


The model has been demonstrated to reproduce the observed variability in rate of rise, hydrograph volume and inundation times.

This study produced a robust framework that allowed SCA and Infrastructure NSW to make informed decisions about mitigation options to protect residents.

Find out More

Mark Babister, Monique Retallick, Melanie Loveridge, Isabelle Testoni,
Carlos Varga & Robert Craig (2016): A Monte Carlo framework for assessment of how
mitigation options affect flood hydrograph characteristics, Australian Journal of Water