2-metre sea level rise a risk in Newcastle's inner-city suburbs

LARGE chunks of Newcastle’s inner suburbs could be underwater by the end of the century if worst-case scenario sea-level rises come true, new flood prediction modelling shows.

Based on new, more dire estimates of “plausible” sea level rises caused by the rapid melting of ice sheets in Antarctica and Greenland, the modelling predicts large chunks of suburbs like Wickham, Carrington and Maryville could be underwater by 2100.

The modelling, from Coastal Risk Australia, is based on new research by the US National Oceanic and Atmospheric Association, which this year released updated projections for sea level rises which reevaluated previous worst-case scenario modelling from a 74-centimetre sea level rise by 2100 to between 2 and 2.7 metres. 

In Newcastle, the modelling shows that a sea-level rise of 2 metres could see swathes of land in Carrington, Maryville and Wickham inundated during high tides, as well as parts of Honeysuckle, Hunter Street and even Newcastle West. 

In Lake Macquarie, the mapping shows potential for significant flooding, particularly in eastern suburbs like Belmont, Swansea and Blacksmiths.

The threat of climate change and subsequent sea level rises have not gone unnoticed by Newcastle City Council, which is currently exhibiting a strategic position paper for managing the issue in the “low lying” suburbs of Wickham, Maryville, Carrington and Islington.

It predicts a small number of private properties in those suburbs could face regular inundation as a result of sea level rises of only 0.3 metres, and said rises of 0.8 metres by 2050 – the 2013 “worst case scenario” – without intervention would see flooding increase across the area and cause permanent waterlogging of particularly low-lying parts”.

The paper does not consider the more extreme flood levels included in the latest coastal modelling, however it proposes that the council spend between $45 and $55 million installing flood gates on stormwater outlet pipes and the construction of a levee along the Throsby Creek cycleway that would “protect the entire area from inundation by sea levels up to 2.5 metres”.

Newcastle Greens councillor Michael Osborne, an hydraulic engineer, said it was a “big risk for the area” that the council needed to invest in. 

Cr Osborne last week presented at the Floodplain Management Australia National Conference held in Newcastle about best practice for councils in dealing with flood planning, and said local government organisations needed to consider the impacts of flooding because they were the bodies liable for damages.

The conference, which heard from flood management experts from across Australia, included a presentation from Daniel Williams, the NSW flood team leader from Broadmeadow-based engineering consultancy firm BMT WBM, about predicting the next major flood on the Hunter River.

Mr Williams told the Newcastle Herald that while major floods in the Hunter’s recent past – i.e. 2007 and 2015 – had come from coastal storms caused by an east coast low, the largest previous flood along the Hunter River in 1955 was the result of the remnants of a tropical depression moving warm moist air across inland Australia and into the top of the Hunter catchment.

He said future climate change predictions suggested it was possible that more events like that could occur in the future.

“As well as sea level rises, which affects Newcastle harbour rather than valley, we also look at potential increases in rainfall intensity,” he said.

He said climate change models included predictions of increasing sea surface temperatures, with a greater level of moisture take up, which would make conditions like the 1955 storm “more common”.

“It's inevitable that there will be more floods like there, but where that uncertainty is, is in how frequently you would expect it to occur,” he said.

“You could be lucky and go 200 or 300 years without a flood, or get unlucky and get two in the next 50 years.”

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