Floodplain Manager July 2018

As drought grips large swathes of Australia, my attention was drawn to the impacts of recent flooding in Japan. While that country appears to be well prepared and drilled for the frequent earthquakes which it experiences, it seems to have been caught unaware by the magnitude of the flooding and its direct and indirect impacts. It may be due to the same mentality which saw widespread devastation from the tsunami in 2011 because it exceeded anything which had been previously recorded and preparations in some locations did not contemplate those consequences or how to respond.  Many towns protected by tsunami barriers were surprised when the tsunami overtopped them.

There are a couple of interesting resources referenced in this edition which explore the phenomenon of the "levee effect” and how that influences human behaviour before and during floods. It is also interesting to read that there is a recommendation to increase flood protection across the UK, adopting a minimum of the 1 in 200 chance per year event but providing 1 in 1,000 chance per year protection in densely populated urban areas.  Meanwhile, New York is rebuilding neighbourhoods devastated by flooding during Hurricane Sandy with apartments which are designed to be flood resilient. Of course the questions remain, "what sized flood are they resilient up to?” and "what happens when that flood is exceeded?”

I am pleased that in many parts of Australia we are expected to consider the consequences of floods through to the probable maximum flood. However, as I have pointed out in some recent matters where I have provided expert evidence, that does not mean that in all cases all potential consequences need to be eliminated.  As with all forms of risk there comes a point where you either accept the risk as being acceptable because the chance of it occurring is so remote or the consequences are not significant, or you tolerate the risks because the benefits of taking on the risks outweigh the costs of avoiding them.

As always, I hope that Floodplain Manager helps inform flood risk management decisions through providing information on the latest research, tools, resources and experiences.

Steven Molino


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