February 20, 2018

Hydraulic Hazard in Floods

The definition of how hazardous flowing water is during a flood is currently based on methods dating back to the early 1970’s.  This methodology has often been criticised as it does not have a clear physical connection to both depth and speed of flowing water. We have conducted research into developing a new approach and although far from perfect, the new approach is extremely promising. It provides for a way to fully automate the definition of hazard through 2D models accounting for both DEPTH and VELOCITY. Existing methods are essentially based on Velocity x Depth ( Momentum) the new approach uses (D+DxV^2) or Dx(1+V^2). This potentially identifies a much greater resolution of FLOOD HAZARD (Hydraulic) Definition.  The initial research findings were published in a paper at the 2008 Floodplain Management Authorities Conference in Wollongong. The paper is also available here: HAZARD_PAPER


  1. Robert French says:

    I had a skim read of the paper but my personal experience of flood waters is that it tends to carry macro-debris, like 200-L drums, trees and other stuff likely to drown one. I was taught as a whipper-snapper not to enter floods on the rising limb because that is the time it is picking up material deposited since the last flood. Certainly I didn’t try to swim a tributary of the Finke River in the Jan/Feb(?) Cyclone Wanda-based 1974 floods until the peak had passed. How you incorporate debris into flowing water hazard I don’t know but there are all sorts of other cute hazards like falling over and having air trapped in warers or pants legs holding one upside down , smashing one’s head on the bed until unconscious or dead. So I guess my question is why continue devising hydraulics based on pure water (except for the 1998 Wollongong flooding for which the local engineers reckon every culvert was plugged with debris like a cork in a bottle)? Don’t ask me how to solve the problem, I’m only asking a question.

  2. Yes you are right, debris in flood water does increase hazard. As does sediment load. There is work currently underway to include sediment, but I imagine that accounting for debris may be some time away for any model…

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