Coastal risks increasing from rising sea levels: IPCC

Image shows an aerial view from Narrabeen to Long Reef on Sydney's northern beaches by Mark Merton.

The Intergovernmental Panel on Climate Change’s (IPCC) latest Special Report on the Ocean and Cryosphere in a Changing Climate  states sea level is rising at an increasing rate, alongside ocean warming and acidification, which will increase risks for low-lying coastal communities and biodiversity.

Extreme ocean levels which historically would occur on average once in a century – what engineers call a one percent inundation level – are projected to occur annually at most coastal locations around the world, depending on by how much further the planet warms, the IPCC said.

“In the absence of more ambitious adaptation efforts compared to today, and under current trends of increasing exposure and vulnerability of coastal communities, risks, such as erosion and land loss, flooding, salinization, and cascading impacts due to mean sea level rise and extreme events are projected to significantly increase throughout this century under all greenhouse gas emissions scenarios,” the final draft report said, citing a “very high confidence”.

“Under the same assumptions, annual coastal flood damages are projected to increase by 2–3 orders of magnitude by 2100 compared to today (high confidence)”.

One order of magnitude is 10 times the damages and three orders of magnitude is 1,000 times, which means this assessment has strong implications for Australia’s almost 60,000 km of coastline and the local councils that manage it. About 80 percent of the Australian population lives within 20 km of the coast.

The new report follows a study by the Western Australia Department of Planning, Lands and Heritage this year that warned erosion at 55 coastal locations may damage roads, buildings and other assets, and managed retreat may be required within 25 years.

The WA study recommended the State Government “provide integrated coastal planning and engineering support to local coastal managers” to prepare detailed Coastal Hazard Risk Management and Adaptation Plans for public and private assets.

The WA Premier, Mark McGowan, said coastal erosion was a national problem which needed a national response, and could not be left to Local and State Governments governments to manage.

The WA Local Government Association said member Councils welcomed the State following their lead in committing to redress the effects of climate change.

A number of local councils around Australia have released or are working on climate change strategies.

The Draft environment and climate change strategy 2040  from Northern Beaches Council (NBC) in Sydney, for example, notes that history has shown – beachfront properties and the Collaroy Beach Club were damaged in storms in 2016 – how vulnerable its 80km of open coastline and 24 ocean beaches are to erosion.

“Our region will be exposed to various climate change impacts such as sea level rise, more intense storms and flooding, leading to increased risks to buildings and infrastructure, heat waves and increased bush fire risk,” the NBC document said.

“While Council and the community will do their bit to mitigate future climate change, managing or ‘adapting to’ expected future risks and changes already locked into the system will help to minimise the extent of impacts.”

One in five properties in the Northern Beaches Council Local Government Area are potentially affected by flooding, while adequate planning may reduce potential disaster recovery costs by a factor of 10.

The Council intends to “ensure the built environment, especially critical infrastructure, is resilient to natural disasters and climate change influences”.

It said Council alone cannot fulfil the strategy’s goals and aspirations, “as many of the actions needed to achieve them fall beyond the direct control of local government,” so strong collaboration and advocacy is needed.

In May, the Climate Council communications organization, estimated that one in every 19 properties around Australia could have “effectively unaffordable insurance premiums” by 2030 because they would cost 1% or more of the property value annually.

The increase in coastal flood damages following future sea level rise as outlined by the IPCC supports this worrying scenario.

Image: Aerial view from Narrabeen to Long Reef on Sydney’s northern beaches, by Mark Merton/Sydney Images/Wikimedia.