The Gold Coast Seaway: The $50 Million Infrastructure Decision That Changed a Coastline
- ICM News
- May 11
- 4 min read
Forty years ago, Queensland delivered one of the most significant coastal infrastructure projects in the state’s history, the Gold Coast Seaway.
Today, it’s often viewed as the gateway between the Broadwater and the Ocean. It is where boats head offshore, where surfers enjoy waves at The Spit, and where locals walk the rock wall promenade.
But before the Seaway was built, this stretch of coastline was unstable, dangerous and constantly moving. The former Southport Bar shifted north by around 60 metres every year as sand moved along the coast. Over time, that migration dramatically reshaped the coastline.
In the 1840s, the entrance was located much further south, roughly where Broadbeach now sits. By the 1930s, it had moved north toward what is now Sea World, prompting the construction of a seawall to protect Southport. By the 1980s, the entrance had moved even further north, eroding parts of South Stradbroke Island and contributing to the loss of the former coastal settlement of Moondarewa.
Without intervention, that movement would have continued.
Angus Jackson saw the challenge firsthand.
“The bar was one of the most dangerous in Australia and sinkings of trawlers and recreational vessels (including one my father’s boats) was common.
Before founding International Coastal Management in 1989, Angus Jackson served as the City of Gold Coast’s Coastal Engineer and later became Director of Beaches and Waterways, helping shape this project, and many of the coastal management initiatives that transformed the city during the 1980s and 1990s.
Reflecting on the recent 40-year milestone, Angus said:
“The seaway and bypass system proved to be a great example of solid coastal engineering founded on a long term local data set that provided in depth understanding of the complex local processes. The original system was very much a pilot project - it worked well but was not perfect. Ongoing monitoring and modifications have improved the efficiency and allowed backpassing that will be critical to the long term sustainability of the GC beaches.”
A long-term coastal management decision
The Seaway was not a standalone idea.
Training the entrance formed part of the Delft Report recommendations and aligned with the City of Gold Coast’s broader coastal management scheme gazetted in 1972.
Council understood the importance of stabilising the entrance, but the project was well beyond local government budgets at the time.
During the mid-1970s to mid-1980s, Council was focused on major city-building priorities, including sealing roads and transitioning the city from septic tanks to sewer collection and tertiary treatment systems that significantly improved water quality.
The Seaway required state support. At approximately $50 million, it was a major investment for Queensland at the time. The State accepted responsibility for design and funding, launching concept designs in 1983 and fast-tracking the project as critical infrastructure.
It was also designed and built by Queensland engineers and contractors, helping build specialist expertise that would later be applied across Australia and internationally.
Solving a dangerous navigation problem
The Southport Bar had become notorious among local boaties. Commercial fishing fleets often struggled to safely cross the entrance. Recreational vessels regularly encountered dangerous conditions. Multiple sinkings and fatalities occurred over the years.
The dangers became impossible for government to ignore when Queensland Treasurer Sir William Knox visited the site to inspect conditions and was injured while crossing the bar.
According to Angus, that moment helped accelerate state support for a permanent solution.
The coastal engineering challenge
Building the rock walls was only part of the challenge. The Gold Coast moves around 500,000 cubic metres of sand northward each year. Without intervention, that sand would have quickly blocked a fixed entrance.
As Angus explained:
“Because of the longshore transport, about a half a million cubic metres of sand every year would have just clogged up the entrance, that had to be pumped across with a fixed bypass system.”
That thinking helped create one of Australia’s most important sand management systems.
The project also required approximately one million tonnes of rock, with some armour units weighing up to 20 tonnes.
“We had truck after truck with those massive boulders,” Angus said.
Why the Gold Coast Seaway delivered exceptional value
The Seaway solved far more than a navigation issue. It:
stabilised the entrance and stopped valuable beach sand being lost into the Broadwater
created deep and reliable navigation access
made millions of cubic metres of beach-quality sand available for beach nourishment and continues providing approximately 80,000 cubic metres annually for northern Gold Coast beaches, helping improve long-term resilience
reduced flood levels
improved flushing and supported higher water quality outcomes
helped unlock Wave Break Island, recreational access at The Spit, and popular surf breaks
also enabled major economic development including marinas, waterfront development and marine industries across the northern Gold Coast
Few infrastructure projects create this level of public return across coastal management, safety, recreation and economic growth.
The Gold Coast coastal management program
The Seaway was not the end of the Gold Coast’s coastal transformation. It became the foundation for many of the strategies that followed.
During his time leading the city’s coastal program, Angus helped advance initiatives that are now widely recognised across Australia, including:
the Tweed River Sand Bypass System
large-scale beach nourishment programs
urban dune management policies
surf amenity planning
the foundations that eventually led to projects such as Narrowneck Artificial Reef
Many of these initiatives were considered unconventional at the time but became reference projects for coastal cities facing similar pressures.
Coastal engineering lessons
The lessons from the Gold Coast Seaway still influence coastal entrance and waterway projects today.
ICM has continued applying similar thinking across Australia and internationally, including entrance and waterway projects in Qatar, feasibility work for a Seaway-style coastal entrance concept in California, and strategic advice for Bribie Island following recent breakthrough events.
At Bribie Island, ICM’s reporting recommended the establishment of a Sunshine Coast Waterway Authority to improve long-term governance, coordination and management of the Pumicestone Passage and surrounding waterways. That recommendation reflects one of the major lessons from the Gold Coast: successful coastal infrastructure needs strong governance, long-term planning and ongoing management, not just construction.
Forty years later, the Gold Coast Seaway remains one of Queensland’s most successful infrastructure investments.
And for ICM, it represents something more personal. It helped shape the career of our founder and the innovative coastal thinking that still guides our work today.
