The Power of Sand Bypassing Systems in Coastal Management
- Aaron Salyer
- Sep 12, 2023
- 6 min read
Updated: May 11
Managing sand movement is one of the most persistent challenges in coastal engineering.
When river entrances, training walls, marinas and navigation channels interrupt natural littoral drift, the impacts are often predictable: erosion on adjacent beaches, shoaling within navigation channels, rising dredging costs and growing pressure on coastal infrastructure.
For more than four decades, ICM founder Angus Jackson has worked on projects where managing sand movement has been central to long-term coastal resilience.
That experience began on the Gold Coast, where large volumes of sand move north along the coastline every year. Understanding how to work with that movement, rather than against it, helped shape some of Australia’s most recognised coastal engineering projects.
What is a sand bypass system?
A sand bypass system is designed to transfer sand from one side of an obstruction to the other, allowing natural littoral drift to continue.
These systems are commonly used where infrastructure interrupts natural coastal processes, including:
river entrances
port developments
inlets
marinas
training walls
navigation channels
Without a functioning bypass system, sand often accumulates at the updrift side of infrastructure while downdrift beaches experience sediment loss and erosion.
Depending on site conditions, sand bypassing methods may include:
fixed pumping infrastructure
dredging and relocation
mechanical transfer systems
periodic sand backpassing
hybrid approaches
Every sand bypass system must respond to local coastal processes, wave climate, sediment transport patterns, approvals requirements and operational constraints.
The Gold Coast: one of Australia’s most recognised sand bypass systems
Few locations demonstrate the importance of sand bypassing better than the Gold Coast. Before the construction of the Gold Coast Seaway, the Nerang River mouth was constantly shifting. Large volumes of sand moving along the coast created dangerous navigation conditions and ongoing instability at the river entrance.
Around 500,000 cubic metres of sand moves north along the Gold Coast every year. Without intervention, that sand would have rapidly filled the entrance.
As Angus explains:
“Because 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.”
The Gold Coast’s sand bypass system helped maintain navigation access while reducing coastal erosion impacts on surrounding beaches. It also became a major reference point for future sand bypass systems around Australia.
"The first fixed jetty mounted system, at the Nerang River entrance, was commissioned in 1986 to provide a safe navigable entrance and has provided proof of concept for permanent bypassing systems in high wave energy environments where dredging was difficult."
Why monitoring matters
A successful sand bypass system is rarely static. Coastal systems evolve, sediment transport patterns shift and operational needs change over time.
That is why ongoing monitoring remains critical.
As Angus explains:
“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 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 Gold Coast beaches.”
That adaptive approach remains central to successful coastal management today. The best bypass systems are monitored, refined and adjusted over time as coastal conditions change.
Littoral transport
Understanding littoral transport is critical when assessing whether a sand bypass system is the right solution. Littoral transport of sediments (generally sand but can be shingles and other beach materials) is a result of the longshore currents generated by waves approaching the beach obliquely.
Understanding these transport patterns helps coastal engineers determine whether fixed infrastructure, periodic dredging, backpassing or broader sediment management programs are more appropriate.
Advantages of Sand Bypassing
Erosion Control: With sand constantly on the move, areas down drift of obstructions can experience erosion. Sand bypassing counteracts this, maintaining beach width and reducing long-term coastal erosion pressures
Navigation: For ports and harbours, sediment build-up can create operational and safety issues
Recreation and Tourism: Healthy beaches support tourism, recreation and surf amenity. On the Gold Coast, bypass systems have contributed to improved surf conditions at several locations.
Economic Benefits: From boosting tourism to reducing the costs associated with dredging, effective systems can reduce dredging costs while supporting tourism, marine industries and coastal development
Environmental Balance: maintaining natural sediment transport can reduce unnecessary disruption to surrounding coastal systems
ICM's Bypassing and Backpassing Experience
Nerang River Bypassing and Backpassing
Angus Jackson, serving as the City of Gold Coast's coastal engineer, played a pivotal advisory role in the 1980s implementation of the Nerang River sand bypass system on the Gold Coast. This jetty-mounted pump system, established by the Qld Government, ensured safer navigation at the notorious Nerang River entrance, benefiting both recreational boaters and the commercial fishing fleet, while preserving natural sand transport patterns.
The fixed system places sand beyond the entrance and is complemented by a mobile dredge that clears sand build-ups in nearby channels. ICM has overseen several of these operations.
This effective system has not only boosted commercial and recreational marine activities, resulting in significant economic gains, but has also enhanced surfing, ensuring even naval vessels can safely access the Seaway.
Tweed River Bypass System
In 1985, Angus Jackson (Jackson 1985) pinpointed the need for a second sand bypassing system at the Gold Coast's southern end. Data revealed significant sand losses due to the Tweed River training walls since 1962, eroding southern beaches and leading to North Kirra SLSC being the only surf club without a beach.
Initiatives began in 1985, focusing on innovative nearshore nourishment to offset these sand losses and address rising sea levels. Research with the University of NSW confirmed the importance of restoring natural sand transport. By 2001, a bypass jetty was established, though occasional dredging remained necessary.
Crucially, dredged sand deposition was executed thoughtfully, enhancing a popular surfing location, creating the "superbank", and ensuring minimal beachgoer disruption.
Tallebudgera Creek and Currumbin Creek
Tallebudgera and Currumbin Creeks presented recurring challenges including sand build-up at their entrances, reduced tidal exchange, flooding risks and water quality concerns.
Angus recognized the multifaceted benefits of sand bypassing. By implementing annual pumping from these creeks, not only was the trapped sand effectively relocated to replenish the beaches, but two critical issues were simultaneously addressed: flood mitigation and water quality enhancement. Removing excess sand would ensure smoother water flow, reducing the potential for floods. At the same time, with improved flow, water stagnation was minimised, leading to healthier, cleaner water in the creeks.
To achieve this, a 12-14’ cutter suction dredge was used, designed to lift and transfer sediment. This dredge continues to support these operations today, helping maintain entrance stability while improving flood capacity and water circulation.
Noosa Main Beach Backpassing System
Noosa Main Beach is one of Queensland’s most recognisable coastal tourism assets, but like many high-use beaches, it requires active sand management to maintain beach width, amenity and resilience.
ICM was engaged to provide coastal engineering advice on a proposed backpass system for Noosa, designed by Slurry Systems. The system was developed to move sand from areas of accumulation back toward areas experiencing erosion, helping keep sand within the local beach system.
Backpassing is a sand management method where sand is mechanically transferred against the dominant net transport direction. In practical terms, it allows a beach system to “recycle” its own sand, reducing net loss and supporting long-term beach stability.
ICM’s role included advising on the preferred location for the system, considering coastal processes, operational efficiency, environmental impacts and approvals requirements. Placement was critical to ensure the system could function effectively while minimising disruption to beach users, local amenity and the surrounding coastal environment.
The backpass system was designed to pump approximately 30,000 cubic metres of sand annually in a southward direction to help maintain Noosa Main Beach.
Today, the system remains an important example of how targeted sand backpassing can support high-value recreational beaches while working within natural coastal processes.
Other Locations
Some other implementation dredge based bypassing systems by ICM include:
Rosslyn Bay Marina
Port Hacking
Scarborough Marina
Woorim
Runaway Bay Canal Entrance
Coffs Harbour
Mooloolaba River Entrance
Working with Coastal Processes
Sand bypassing is most effective when it works with natural coastal processes rather than against them.
As Angus explains:
“Sand bypassing systems can be synchronous with the sand transport, such as a fixed pump system, or intermittent, such as by a mobile dredge that recovers sand ‘lost’ into a natural or man-made tidal entrance, such as a harbour.”
This flexibility is important. Different sites require different sand bypassing methods depending on wave climate, sediment transport, navigation needs, environmental constraints and available infrastructure.
The benefits can also extend beyond coastal management alone. As Angus notes:
"With appropriate discharge locations, sand bypassing systems can improve surfing, such as the Superbank, and provide substantial economic benefits.”
For ICM, sand bypassing remains an important part of the coastal engineering toolbox. When designed and managed well, a sand bypass system can help maintain natural sediment movement, reduce coastal erosion, improve navigation, support beach amenity and work alongside nearshore nourishment and artificial reefs.
The Gold Coast remains one of the clearest examples of this integrated approach in practice.
Contact us about Sand Bypassing
Sand bypass systems are not one-size-fits-all. The right approach depends on local coastal processes, sediment transport patterns, navigation requirements, environmental constraints and long-term maintenance considerations.
ICM has advised on sand bypassing, backpassing, dredging and coastal entrance management projects across Australia and internationally.
If your project involves coastal erosion, entrance instability, sediment build-up or long-term beach management, contact our team to discuss practical solutions.
