Australian Floodings

DHI hydraulic model providing insight in Australian floodings

Rapid Flood Hazard Assessments application providing information suitable for emergency and strategic planning purposes.

The 2010 / 2011 wet season has so far been the most devastating in over 30 years for large regions of Australia, especially Queensland and northern New South Wales.

Detailed flood studies have been undertaken for many parts of Australia. However, these are generally focused on large urbanised areas where the economic consequences of floods are significant. Yet flood risks may be apparent in the many smaller, rural communities scattered throughout the country. Undertaking detailed flood studies for each and every community would be prohibitively expensive and very time consuming.

The solution is a rapid assessment that can be applied over a large geographical extent in a short time. DHI have pioneered the application of so called Rapid Flood Hazard Assessments that aim to provide a sufficient level of flood hazard information suitable for emergency and strategic planning purposes. The technique utilises a two-dimensional hydraulic model (MIKE 21) of the catchment surface upon which rainfall is directly applied. The technique removes the need to develop a separate hydrologic model.

The main advantages are:

  • Fast results, very little pre-processing;


  • Production of hydraulically consistent flood inundation maps, showing depth, water velocity and hazard;


  • Outputs are highly visible and easily understood by non-specialists; and


  • Animations showing the timeline of the evolution of the flood can be produced.


Whilst the approach is a simplified one, our experience has shown the method capable of reproducing the most important aspects of flood behaviour.