May 26, 2020 @ 1:00 pm – 1:45 pm

Topic: (Im)probable Maximum Flood

Presenter: Rick Dennis, Principal Engineer, Allan & Dennis.  Rick specialises in hydrology, hydraulics, water quality, flood management and stormwater infrastructure

Date:  Tuesday 26 May 2020

Time:  1.00pm – 1.45pm

Presentation Summary: Flood design approaches have recently changed from standards-based (ie Defined Flood Level) to risk-based (probability and consequence).  This has resulted in the requirement of rare flood consideration up to the Probable Maximum Flood (PMF) for most applications.  Whilst the PMF appears a simple enough concept, in practice its consistent estimation is difficult.

Furthermore, a PMF cannot be assigned a specific probability (as it is a function of catchment area), and therefore not strictly appropriate to a consistent risk-based approach.  Moreover, with the recent Australian Rainfall & Runoff (ARR) 2019 update, there is an even greater disconnect between design event and PMF methodologies.  The concept of ‘reasonableness’ with respect to PMF is advocated in ARR2019.  However, as engineers are generally conservative, the adoption of the PMF for design approaches are becoming more common.

This is resulting in disproportionate costs and significant restrictions in development and that would otherwise be appropriate to the flood risk.  A short introductory presentation will summarise current best practice methodology, recent implications, and other design standards in order to provide a basis for an interactive and robust discussion with all attendees.

Registration:  This webinar is FREE of charge to all & will be recorded and made available after the session.  To access the Webinar, simply open this link at 1pm on May 26: