Artificial Reefs and Nearshore Nourishment on the Gold Coast: Real-World Results
Updated: Oct 14
The sun-kissed beaches and world-class surf breaks of the Gold Coast have long been regarded as the unrivaled crown jewels of Australia's coastal landscape. The Gold Coast is one of the most popular tourist destinations in the country. However, preserving this coastal charm requires more than nature's hand; rather, it necessitates creative and environmentally responsible approaches to coastal management.
Artificial Reefs, Nearshore Nourishment and Bypassing Systems are at the forefront of these advancements. These initiatives were spearheaded by the efforts of Angus Jackson in the early 80's (as the Gold Coast City's Coastal Engineer) and subsequently by International Coastal Management (ICM), his post-council consultancy.
The Need for Change
Historically, the Gold Coast's coastline was shaped and reshaped by the forces of nature—storms, tides, and currents. However, as the 20th century progressed and urban development surged, the natural equilibrium of these beaches began to waver. The 1960s and 70's bore witness to this delicate balance tipping, as severe swell events became more frequent, causing significant erosion and threatening both the natural beauty and the burgeoning tourism industry of the region.
Traditional coastal erosion solutions, such as dredging and beach nourishment, became the immediate recourse. While these methods provided temporary relief, they were just that—ephemeral. The recurring costs, both financial and environmental, of these interventions were becoming untenable.
It was in this challenging backdrop that visionaries and coastal management experts began to explore alternative, sustainable solutions. The focus shifted from merely reactive measures to proactive, long-term strategies. The idea was not just to combat erosion but to enhance the coastline's recreational and ecological value looking at more nature based solutions. This forward-thinking approach set the stage for innovations like artificial reefs—structures designed to promote sand accumulation and dissipate wave energy, thereby reducing erosion.
Piloting for Success
Instead of just putting solutions into place, the Gold Coast used a process of piloting and monitoring. With this proactive plan, the area became what could be called a full-scale coastal laboratory.
With each project, a lot of monitoring and feedback loops were set up so that real-world results could be used to guide future projects. Because of this commitment to solutions based on facts, the Gold Coast has become known around the world as a model for smart and flexible coastal management.
A series of landmark projects chart the path of the Gold Coast's transformation:
Narrowneck Artificial Reef
Serving as both a coastal protection measure and a surfing amenity, this reef became a benchmark in artificial reef design. Continuous monitoring has shown geomorphological changes to littoral sand drift. This has caused a buildup of sand around the reef, helping to reduce erosion and offering added surf benefits on sandbanks. Notably, the reef was constructed using geotextile sandbags, which were approximately 1/3 the cost of a rock reef construction. This cost-effective approach was consistent with the pilot nature of the project.
Demonstrated successful use of geotextile sandbags, offering cost-effective reef construction.
Induced geomorphological changes, leading to sand build-up around the reef.
Reduced coastal erosion and enhanced surfing conditions due to formed sandbanks.
Here are some extracts from the latests scientific review of Narrowneck Reef after 20 years and the way that it interacts with the sand morphology. From the paper "Sediment pathways and morphodynamic response to a multi-purpose artificial reef -New insights"
"Twenty years after Narrowneck construction, the MPAR has shown a localised effect on the nearshore morphology that helps to maintain the beach in a similar state compared to the adjacent areas whereas it was previously more vulnerable (i.e. a hotspot). Sediment transport pathways are shown to occur both inshore and offshore of the reef, under varying hydrodynamic and morphodynamic conditions. This study has identified scenarios whereby a previously unforeseen deposition of sand downdrift of the reef occurs in the sub-tidal region."
"The deposition process, associated with the presence of the MPAR, aids in coastal protection by dissipating incoming wave energy, before it reaches the shoreline and provides a temporary sediment store to feed the downdrift areas (Figure 36-8) in a process that is akin to headland sand bypassing (Short and Masselink, 1999; Klein et al, 2020) and moreover, it is closely linked to the wave height and direction (Vieira da Silva et al., 2018b). This is likely the reason why the downdift erosion expected during design phase (Turner et al, 2001) has not been observed in the data."
"Twenty years after construction, the Narrowneck reef site has more sand deposited updrift and the longshore transport seems to have re-established with minimal impacts on the upper beach. The location of the reef within the active surf zone worked as planned allowing sand to bypass inshore of the reef, particularly under modal wave conditions. Although not initially expected, the results presented in this work demonstrate that the sand bypassing can also occurs offshore of the structure under certain conditions (large oblique waves). Whilst a persistent salient at the shoreline was not observed in the dataset presented here, Narrowneck reef evidently does affect the sediment transport and morphological changes in the short-term, helping to sustain the overall medium to long-term increased volume of sand while allowing sand to also bypass the reef and continue downdrift without significant negative impacts."
"The short-term morphological response to the MPAR after two decades is more closely related to the deflection of longshore currents as they encounter the reef than to the dissipation of wave energy, mainly because MPARs are designed to dissipate just enough wave energy so that the wave can still be surfed."
Sand Bypassing Systems (Nerang and Tweed Rivers)
Recognizing the importance of maintaining navigational access and natural sand flow, sand bypassing systems were established at both the Nerang and Tweed Rivers. They've led the way in coastal management, with additional benefits observed in surf conditions at places like the Superbank and South Stradbroke Island. These systems not only ensured uninterrupted sand delivery to nourish southern beaches but also played a pivotal role in mitigating erosion.
Pioneered sustainable coastal management, ensuring uninterrupted sand delivery.
Improved navigational access and natural sand flow.
Enhanced surf conditions at iconic spots like the Superbank and South Stradbroke Island.
Palm Beach Artificial Reef (PBAR)
Informed by the monitoring results from Narrowneck, PBAR was completed in September 2019. Recent Wave Peel Tracking (WPT) has shown the development of sandbank surf breaks around the reef. Ongoing surveys also indicate that the nourished sand remains retained around the reef, enhancing the coastal landscape and supporting its recreational potential.
Used monitoring results from Narrowneck for informed design and implementation.
Wave Peel Tracking (WPT) indicated the development of desirable sandbank surf breaks around the reef.
Ongoing surveys showed retained nourished sand around the reef, indicating long-term effectiveness.
The 2017 Gold Coast Beach Nourishment Project (GCBNP)
Spanning June to September 2017, this project added over 3 million cubic meters of sand to the Gold Coast's beaches. The project utilised the novel nearshore nourishment approach to achieve high volumes. Survey results five years post-implementation indicate that a commendable 75% of the nourished sand at Palm Beach still remains within the system. This retention is believed to be due to the combination of nearshore nourishment and the Palm Beach reef, which have jointly contributed to sand retention despite facing significant storms over the past half-decade. This project was built on decades of research and development in the field of mass nourishment, led by Angus Jackson and ICM.
Successfully added over 3 million cubic meters of sand to vulnerable beach sections.
Five-year post-implementation surveys revealed 75% of nourished sand at Palm Beach still within the system.
Proved the combined efficacy of nearshore nourishment and the Palm Beach reef, retaining sand even after significant storm events.
Some Key Successes
The accomplishments stemming from these projects are manifold:
Sustained Sand Retention: Post GCBNP, a remarkable 75% of the nourished sand remained active within the beach system, underscoring the project's efficacy.
Revitalized Surf Conditions: The emergence of surf-conducive sandbanks adjacent to the artificial reefs, especially the right-hander near PBAR, bolstered the region's recreational appeal.
The Road Ahead
The tale of the Gold Coast's artificial reefs and nearshore nourishment is one of innovation, resilience, and sustainable progress. However, as any coastal engineer or environmentalist would attest, coastlines are inherently dynamic zones. Their ever-changing nature, shaped by tides, currents, and human activities, mandates a proactive and adaptive approach to management.
As we stand at the cusp of a future marked by climate change challenges, the significance of ongoing monitoring cannot be understated. The lessons learned from each project on the Gold Coast serve as stepping stones, guiding the next phase of innovations. The insights gleaned from the past become particularly vital as we grapple with the looming threats of sea-level rise and increased storm events. Predicted changes, fueled by global warming, will undeniably reshape our coastal landscapes, making the field of coastal engineering even more crucial.
Building upon the foundation laid by trailblazers like Angus Jackson and the entire team at International Coastal Management (ICM), the future will see coastal management strategies that are not only reactive but also anticipatory. Harnessing the symbiotic alliance of science, engineering, and the nature based solutions, we can ensure the Gold Coast's legacy endures, not just as a testament to its past glories, but as a beacon of hope and resilience in the face of future challenges.
An acknowledgment is due to the Gold Coast city and their dedicated team, both past and present. Their unwavering support and openness to pilot projects have been instrumental in advancing coastal management strategies. Their emphasis on rigorous monitoring and development has set a benchmark for other coastal regions to emulate.
Additionally, a special mention goes out to the consultants and contractors who have seamlessly integrated into the Gold Coast coastal management team. Their expertise, commitment, and collaborative spirit have been invaluable in shaping the Gold Coast's legacy as a pioneer in sustainable coastal management.