Australia’s coastlines are naturally dynamic. Processes of erosion, transportation and accretion (the build-up of sediments) shift and shape the coastline. Erosion can have dramatic impacts during storms, when winds and waves are strong. But this is often just a short-term impact, with sediment gradually regained over weeks and months, either dumped back by the sea or deposited from inland sources via rivers and creeks.
These processes are largely driven by climate and climate driven ocean processes — currents, wind, waves and storms. These climate drivers mean our coastal areas are already vulnerable to damage. Climate change will worsen those risks.
What will be intensified and changed by the climate emergency?
Climate change will bite in a number of ways. Sea level rise combined with intense storms pose the greatest erosion and damage risk. Sea level rise increases the height of waves while storms generate powerful waves and winds that produce storm tides and as a result, erosion.
Wave climate is also likely to change — although this can both increase or decrease erosion. Likewise changes in rainfall and runoff can go either way. Dry conditions will reduce sediment run-off, while high intensity rainfall increases landward erosion and run-off.
The recent drought, fire and subsequent storms demonstrated what the combined impact of these extremes might look like.
What do impacts and risks look like?
Urbanisation, industrial development, and recreational pressures have transformed the coastal zone. In some places, public foreshore reserves act as a buffer to settlements. In other places, homes and businesses are directly exposed to coastal risks.
Erosion of dunes and beaches can cause damage to structures by reducing the stability of foundations, settling buildings or directly undercutting structures. At its worse this might mean properties collapsing onto beaches.
Recreation facilities like beach access stairs, pathways, and parks are on the front-line, but surf lifesaving clubs, roads, businesses and homes are at risk too. Any damage is likely to be both expensive and inconvenient. For some properties or structures there may even become a point at which it becomes more cost effective and practical to relocate.
So how do we prepare?
As a community, we have to start deciding what must be protected, and how and when; where we will let nature take its course; how and if we need to modify the way we live and work near the coast; and so on.
The first challenge is deciding where and what the risks are. While we know the whole coastline will experience the impacts of climate change and sea level rise, the impacts will create different risks. Sandy coasts are much more vulnerable to erosion than rocky coasts; wave climate differs from place to place; different parts of the coast have more or less development etc.
Climate projections, particularly at the local level, come with a degree of certainty and probability. The further we look into the future, the more extraneous factors are unknown — for example, will global policy succeed in bringing down greenhouse emissions so we can plan for two degrees of warming? Or will emissions continue to increase so we must plan for four or five?
The second challenge is to decide what we are prepared to live with. In adaptation we talk about four responses.
Avoid the risk — don’t build there
Accommodate the risk — build but design for the risk
Protect against the risk — engineer defences like seawalls
- Retreat from risk — plan to move out of harm’s way.
For existing home owners, protection tends to be favoured. It’s understandable, but aside from the cost, if Australia builds a seawall fortress, we risk losing exactly what we love about our coastline.
The alternative for existing properties is managed or planned retreat. But this is a highly contentious approach. The Byron Shire Council adopted a policy of “planned retreat” in the 1970s, but has found that private property owners are fiercely protective of their property rights and are fighting for protection measures.
It’s clear that our coastal communities will be radically changed, and we are seeing these changes already. The way forward demands difficult conversations and challenging decisions. While scientific information is essential to understand the risks and impacts, communities and governments must continue to come together to map a path through many competing interests and views to plan the future for their coastal towns.
Dr Sarah Boulter is a research fellow with National Climate Change Adaptation Research Facility.