Experts agree seawalls can be effective in protecting infrastructure against erosion caused by waves and storms. However, building seawalls remains a contentious issue. Research shows they can play a role in the disruption of natural processes that lead to the erosion of sand sediment from beaches.
So, should seawalls be built or avoided? According to Professor Rodger Tomlinson, Foundation Director of the Griffith Centre for Coastal Management at Griffith University, criticising the use of seawalls oversimplifies a very complex issue.
“These things often fall out into simple arguments – ‘seawalls cause erosion, therefore they’re bad things’. But if you look at the history and why they’re used and what the alternatives are, invariably if they are not used, infrastructure will be damaged,” he says.
“Generally speaking, there are members of the community who don’t like the idea of a seawall. There are other options, of course. However, beach nourishment programs and programs that retreat or remove buildings and infrastructure often fall to the wayside in the interests of protecting private property.”
There are many cases where seawalls have very little detrimental effect, Tomlinson explains. “For example, seawalls have been used effectively to protect infrastructure around Sydney Harbour and on the Gold Coast where a 30km seawall buried beneath the sand forms part of a long-running and effective coastal-management program,” he says.
Other cases indicate both a protective and disruptive outcome. Tomlinson cites the example of the contentious Johnson Street Seawall in Byron Bay, which was built in the 1970s to protect infrastructure from erosion. The wall did its job but is now being blamed for erosion further along the coast. “Recently a natural process variation has required a wall to be built further to the east, closer to Cape Byron,” he says.
“Of course, a lot of people think if you build a wall you will create erosion, but it doesn’t work that way. To quote a colleague, ‘Seawalls don’t cause erosion, erosion causes seawalls.’ What he’s saying is that when your assets or property are under threat and your coastline is eroding and the primary objective is to protect your property, then invariably a seawall will come out as the most cost-effective option.”
So, are revetment walls the answer to protecting vulnerable coastal communities? Tomlinson says it depends on the location and how the local community makes decisions, but the cost-effectiveness of seawalls makes them popular. He believes demolition programs that don’t include a buyout of the entire affected area won’t solve the ongoing problem of coastal erosion.