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Sea level rise: why policy might leave thousands stranded

Areas in Melbourne that would be affected by a 1.1-metre sea level rise, according to the new Coastal Risk Australia tool. See http://coastalrisk.com.au/ to use the tool to see how sea level impacts on your area

Coal mines are not the only investments that may become stranded assets due to climate change – there could be more than 250,000 beachfront properties around the nation that face the same fate. State by state and council by council, policies vary in terms of altering planning rules to prevent more properties being built in places that are risk-exposed. Following is the start of a series on sea level rises and what you need to know.

There currently appears to be no national framework directing the protection of assets and the investment they represent from the impacts of rising sea levels, more frequent storm surges and increased erosion in the coastal zone.

A 2009 assessment by the now-axed federal Department of Climate Change estimated up to $63 billion (in terms of replacement value) of existing residential buildings are at risk of inundation from a 1.1-metre sea-level rise, with a lower and upper estimate of risk identified for between 157,000 and 247,600 individual buildings.

The Climate Change Risks to Australia’s Coasts – a first Pass National Assessment looked at the level of risk for costal property at up to 1.1m sea level rise.

“With a mid range sea-level rise of 0.5 metres in the 21st century, events that now happen every 10 years would happen about every 10 days in 2100,” it states.

“The current 1-in-100 year event could occur several times a year. For illustration, a current 1-in-100 year event is equivalent to the intensity of storms along the New South Wales central coast in June 2007 when more than 200,000 homes lost power, thousands of people were forced to evacuate their properties, and insured losses exceeded $1.3 billion.”

By 2012, the estimate of replacement value had climbed to up to $71 billion in 2008 dollars and up to 277,000 properties. And we still aren’t seeing a national slow-down in development in beachfront, erosion-prone areas.

The state of planning for sea level rise in Queensland

In Queensland, detailed plans are being prepared by many councils following the Labor government’s reinstatement of climate change and sea level rises in planning policies and guidelines. The state policy instructs councils to plan for a 0.8m rise – not quite the 0.9m the ninth IPCC report recommends.

Erosion prone areas were declared in July 2015. These are the zones that are vulnerable to coastal erosion and tidal inundation from the combination of sea level rise and increased frequency of severe storm events.

The erosion prone area plans developed for each council s area are to be used as part of the development assessment process and to inform the development of planning schemes and regional plans.

What the plans can’t help with, though, is protecting existing properties in the at-risk areas of the Queensland Coast.

Each council is formulating its own strategy for adaptation. Gold Coast City Council, for example, has been considering a sea wall along the entire stretch of the developed coastline. In a case study on the proposal, the cost of the wall had been estimated at around $57 million in 2012.

However, sea walls are not necessarily a silver bullet. The case study quoted Alan Jones from the Australian Museum, stating “if hard engineering is used to defend societal assets against erosion, the local sandy-beach habitat would be fundamentally altered, perhaps removed entirely”.

Sea walls can also worsen erosion elsewhere by fundamentally altering the movement of sand and sediments and tidal patterns.

One of the other issues is that sea level rise and erosion do not have a one-for-one relationship.

In the 1960s Danish civil engineer Pers Brun published research showing that shorelines generally recede horizontally at up to 100 times the magnitude of any sea-level rise. If this theory holds true, the mid-range sea level rise projections for 2090 could result in the Gold Coast shoreline receding by anything from 15 to 65 metres.

Scientists say planning flying blind

Scientists at the University of NSW have warned, however, that regardless of plans being made, most local governments were essentially “working blind” in terms of understanding the majority of the nation’s settled coastline.

Researchers at the UNSW Water Research Laboratory have been tracking the trends in coastal erosion at Narrabeen-Collaroy in Sydney since 1976 using drones, real-time satellite positioning, cameras, airborne LiDAR and quad bikes.

The data has shown how climate change is altering the coast, including how El Niño and La Niña cycles will increasingly intensify coastal hazards, leading to a rise in storm events, extreme coastal flooding and erosion in populated regions across the Pacific.

But the researchers said the data is only reliable for computer modelling when it comes to predicting effects in southeastern Australia, not the vast bulk of Australia’s 25,760km-long coastline.

Researchers – and the governments and coastal communities they advise – are making guesses based on largely non-existent data, the UNSW team said.

“The wealth of data we’ve collected consistently over decades makes our models of coastal variability increasingly more reliable – but only for a 500km stretch of southeastern Australia,” said Professor Ian Turner, director of the Water Research Lab at the School of Civil and Environmental Engineering at UNSW.

“But when it comes to modelling other parts of Australia, we are basically working blind. There are very different coasts exposed to very different conditions, and we just don’t have the observational data we need to make predictions with any great confidence. For that, we need a National Coastline Observatory.”

Dr Mitchell Harley, a senior research associate at the lab who manages the Narrabeen-Collaroy program, said that beach erosion and coastal variability was a lot more complex than had originally been thought.

“It’s now clear that sea level rise is not the only player in climate change. Shifts in storm patterns and wave direction also have consequences, and distort or amplify the natural variability of coastal patterns,” Dr Harley said.

“Our data has been pivotal in understanding this. But it’s also made it clear that, to predict the future changes with any degree of reliability around Australia, we need data from other parts of the country. And currently, this is lacking.

“For the great majority of Australia’s coastlines, we don’t have observations for how they are behaving now ­– let alone alone any idea how they might respond to increasing variability in the future.

“We see it happening at Narrabeen-Collaroy, and can therefore predict it for this part of Australia. But elsewhere, it’s really anybody’s guess.”

Gathering data in South Australia

One local government in South Australia has taken steps to begin mapping and assessing the state of its coastal zone.

The City of Onkaparinga on the southern fringe of Adelaide has 30 kilometres of coastline that is extremely vulnerable to coastal erosion. The council recently allocated $50,000 to a mapping and modelling project carried out by Bentley Systems.

The project involved AEROmetrex capturing imagery by helicopter. Then, using Bentley’s ContextCapture, 25,000 oblique photographs and 125 ground-control points were processed to create a detailed 3D mesh that ensured model accuracy of 100 millimetres. This process allowed volume, distance and texture, and visually identified rocks, ground types and the various structures.

By capturing imagery at different points in time, the council can analyse the current state and condition of the coastline and also detect changes in condition. This in turn allows council to assess safety concerns, as erosion is already encroaching on people’s property.

The South Australian government has a Premier’s Climate Change Council that includes experts across finance, clean tech, planning, law, governance, local government, stakeholder engagement and environmental science.

Under the state policies, regional adaptation plans are being developed by many local governments.

The Eyre Peninsula Adaptation Plan has identified a number of impacts relevant to property owners. These include changes in rates of deterioration of roads and pavements; a reduction in stormwater drainage capacity due to sea level rise and storm surge damage; increased frequency of inundation of coastal infrastructure and utilities, including water, sewerage, gas, telecommunications and electricity; and increased uncertainty in long-term land-use planning and infrastructure design.

“A major concern for the Eyre Peninsula is coastal inundation as a result of the combined effects of sea level rise, storm surge, run-off from storm events and land subsidence. A number of council development plans explicitly address the extent of sea level rise that must be taken into account for development planning purposes,” the plan states.

The plan identifies a number of potential adaptation strategies:

  • planned retreat, which involves refocusing development and settlement on land and structures in areas less vulnerable to the impact of sea level rise. This could be achieved through development plan policy and relocating existing infrastructure and houses
  • accommodate, focussing on the implementation of building codes and design standards that require development to be able to withstand periodic inundation, for example through minimum flood heights, foundation design requirements, enhanced drainage and evaporation provisions, building on pilings, demountable homes, adapting drainage schemes to allow flood waters to drain more quickly without impacting receiving environments
  • building emergency flood shelters in high risk areas as well as early warning and evacuation systems
  • requiring hazard insurance for all properties at risk
  • requiring home buyers to be informed of risk at property purchase
  • changing agricultural crops or pasture to more salt tolerant species in areas prone to coastal inundation
  • Prohibiting clearance of coastal vegetation, damage or disturbance to coastal wetlands
  • protect and defend, using hard (e.g. sea walls) and soft (e.g. dune restoration) structural options protective works to defend vulnerable areas, population centres, economic activities, infrastructure and natural resources
  • do nothing, where buildings are seen to have reached their ‘expiry date’ once sea level rise has encroached, properties are abandoned and losses and damages are the owners’ responsibility
  • capacity building, through developing and sharing information, resources and decision making tools regarding adaption options, clearly communicating potential risks when the information becomes available and sharing understanding within the community on the need to adapt

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