Severe coastal erosion in Wamberal, one of Sydney’s well-heeled suburbs, has been devastating. There are literally homes hanging over the edge of collapsed shorelines. This is more than a bit of a blow to the high-end coastal property market, where properties are routinely valued in multiple millions of dollars.
A truly tough problem
It’s an existential crisis, and it’s getting worse. The problems are that big money and financial commitments are involved, and the risks to residents are truly horrendous. This isn’t just a matter of putting up seawalls. It’s a need to thoroughly assess risks to very large areas of coastline.
Collaroy’s problems in 2016 are a good example of what happens and doesn’t happen. Photos show whole areas of soil which have simply collapsed. This type of soil isn’t solidly packed; it’s typically basic topsoil. The soil simply can’t take severe pressure from wave action. Soil types can be truly deadly in this regard. Now add the fact of multiple soil types around Australia, and you can see how tricky these issues can be.
Add to this the rising sea levels. 2cm of added sea level may seem trivial, but those 2cm contain added tonnage of sea water with every single wave. So the pressure of the direct hits on the coastline are rising exponentially.
So, what do you do about it? You can try seawalls, big piles of rocks to block the waves. Seawall failures, however, raise more issues and they’re not always the instant fix. You can build them out to minimise the impact of the waves. You could try the Dutch land reclamation techniques, although it’s a rather different marine dynamic. (Marine dynamics include everything from currents to rips, local coastal formations, etc. It’s a virtual dictionary.)
You’re also talking about spending billions of dollars, nationwide, which local councils don’t have. On the macro scale, the costs are open-ended. That’s the absolute last thing any local, state or Federal government wants to hear.
From a purely engineering point of view, seawalls are at best an acquired taste. There’s a famous case of a big seawall in Scotland which contained an 800 ton rock for a century or so until a wave smashed that rock to pieces. It was replaced by a bigger 1600 ton rock, which was duly pulverised in a few weeks after it was installed. The sheer power of the sea is the difficulty. So you can spend billions on seawalls which may or may not work, too.
In Sydney, the coastline includes huge rock cliffs and pretty average low-lying beaches. It’s a bit of a raffle for geoengineering, and you simply can’t overstate the degree of difficulty. Whether it’s policy or structural engineering, the problems are huge.
The risk to residents
Residents are at a horrifying level of risk. One wave could destroy a home and a family with ease. The damage at Collaroy and Wamberal doesn’t need explaining. We’re lucky nobody was killed in both cases.
That’s not all those waves can do. Undercutting land with structures on it may not be so visible. Large amounts of coastline can literally collapse in landslides. Massive damage is quite possible, and even basic checks for ground stability and safety can take time.
Residents may also be at risk of lack of insurance coverage. Insurers may or may not include these risks in policies, for obvious reasons. (Natural disaster hazards are a sore point for insurers. Floods and bushfires, for example, may or may not be exempted in some policies, and it’s a serious legal issue.) The new, very serious, event may well also hit residents with massive premium hikes, or notifications that they’re not covered.
Local and regional engineering issues
Local engineering to manage coastal erosion can’t be piecemeal. You can’t have one property protected and the one next door not protected, for example. The big costs are a major obstacle to systemic local management. The logistics of sticking a big seawall anywhere can be complex, too, and time-consuming. A wave could hit while you’re waiting.
Regionally, these issues expand into bigger money, more problems and some very tough calls on what’s done, where and when. You can expect fully justifiable screams from residents where they’re not getting quick action, of course.
All this applies without even mentioning the wider issues. What happens when the sea comes flooding in in ever-increasing tide levels? Can you even build an effective seawall, or would you be better off with another alternative like an offshore “brake” on waves to reduce their size and velocity?
Then there’s the unique issue of specific locations where the beach is the place to go. For decades, Australian beaches have been hit with everything from vanishing sand to coastal erosion. Quick fixes may or may not work. You can see how complex this gets when you have both property prices and tourism based on a beach.
Strategy
This problem is no longer avoidable. It’s not just here and there. It’s happening along Australian coasts on a daily basis. A consistent national strategy needs to be developed, based on proven fixes to multiple issues. It may or may not be necessary to preclude some areas from development due to risks. Some areas may have to be declared hazardous, although nobody will like it.
High risk areas must be identified, and a national management strategy must be in place. There are areas on the east coast where tens of billions of dollars’ worth of residential and commercial space are at obvious very high risk. States and local governments will have to be in a position to manage risk, or devolve risk on the Federal government where it’s beyond their capacity to manage.
Residents and commercial interests should receive top priority in any policy. The physical dangers are too real, and the financial dangers too potentially catastrophic, to ignore.
