Mitigating flood risk

University of Adelaide research looks to  protect coastal towns

ALTHOUGH flooding is the last thing on our minds during summer, floods have caused damage along local coastal environments in recent years.

University of Adelaide researchers are now devising new methods to more accurately determine long-term flood risks across Australia.

Local coastal environments such as Parham, Webb Beach, Middle Beach and Thompson Beach could be considered in future flood prevention and beach erosion planning.

Multiple causes of floods have not previously been considered; however, many larger floods across Australia have been extremely complex with many contributing factors. 

Senior lecturer at the University of Adelaide, Dr Seth Westa, said the 2011 Queensland floods superficially appeared to be caused by intense rainfall, but the flood wouldn’t have had been so large if the catchments hadn’t already been waterlogged from a very wet spring.

“Accurate assessment of the risk of floods in any particular area is important for town planning and council zoning and in designing flood protection infrastructure like bridges and levees,” Dr Westra said.

“But properly understanding the risk of flooding means we have to assess the likelihood of these different events coinciding – acting together in a synergistic way to cause an extreme flood.

“For example, do you tend to get big storm surges at the same time as heavy rainfall?

“We need to be able to assess what sorts of floods can possibly occur in the future, even if we haven’t observed or recorded similar events.

“In Australia, this estimation is complicated further by the fact we don’t have great long-term records of flood risk.

“We’re a relatively new country, and in a lot of catchments there may only be 30 years of good data, so we have to make educated guesses as to what might be possible in the future.”

Climate change is adding another dimension to the difficulty of flood risk estimation.

“Under climate change, each risk factor will probably change in the future – but it will be a complex picture, much more nuanced than is often reported,” Dr Westra said.

“Certainly some places will see increased floods, but other locations could even see a reduction in flood risk.”

Historically, storm surges that have threatened coastal towns in our region have been in conjunction with king tides which, in most cases, would have provided more than 12 hours of warning.

In May 2013, Uni SA was commissioned by the District Council of Mallala (DCM) to conduct a Coastal Adaption study, which evaluated how rising sea levels will impact on local beach environments.

The study framework showed potential for improvements in all the areas. Levee repairs at Parham have since been taking place in the past six months.

The community was invited to provide their thoughts and opinions at a community workshop in May.

Christine Kelly of the District Council of Mallala said there have not been any developments on the flood plan for the council.

Further discussion on the matter is expected from council as the proposed adaptation strategies for stage 3 aim to protect, accommodate, retreat and abandon the settlements – or defer and wait and see what happens.

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