One surprising finding from the review of the state of hydrologic practice in Victoria, is that climate change impacts on flooding are not being widely considered. Only half the studies reviewed (10 of 20), mention climate change. Similar findings are reported in other work that shows some Victorian flood managers are not keeping up with their national and international colleagues in considering the additional flood risk predicted with a change in climate.
There is already evidence that rainfall intensity for short duration storms is increasing, which could lead to more frequent and larger flash floods. This is a particular issue in towns and cities because small urban catchments are especially vulnerable.
In the corporate world, consideration of climate change is being taken seriously. The recent Hutley opinion found that many climate change risks “would be regarded by a Court as being foreseeable at the present time” and that Australian company directors “who fail to consider ‘climate change risks’ now, could be found liable for breaching their duty of care and diligence in the future”.
The Task Force on Climate Related Financial Disclosures (TCFD), chaired by Michael Bloomberg, has recently released recommendations on how companies should report on climate change risks. This includes the need to report on risks of “Increased severity of extreme weather events such as cyclones and floods” and “Changes in precipitation patterns and extreme weather variability”.
In the Australian flood scene, the latest Handbook 7 – Managing the floodplain: a guide to best practice in flood risk management in Australia – provides advice on assessing and reporting on climate change risk. But the accompanying project brief template and guide, describe climate change aspects of a flood investigation as optional. The latest version of Australian Rainfall and Runoff provides recommended approaches to assessing climate change impacts on flooding but recent research argues these methods are too conservative.
On a positive note for Victoria, the Floodplain Management Strategy does encourage consideration of climate change (Policy 9A):
Flood studies prepared with government financial assistance will consider a range of floods of different probabilities, and the rarer flood events will be used to help determine the location’s sensitivity to climate change. Further climate change scenarios may be considered where this sensitivity is significant.
Flood investigations lead on to decisions about land use zoning and design of mitigation works. Are climate change risks to these measures foreseeable at the present time? If so, then they should be considered and reported on.
Clearly this is an area where knowledge and ideas are changing rapidly. Practising hydrologists need to keep up with latest methods, and managers and boards of floodplain management authorities need to be aware of the latest thinking on governance, risk management, and disclosure.