With the dredging of the Kingston Pier locale likely going ahead in 2026, and the baseline monitoring buoys being deployed this week, I’ve had lots of people who have been taken by surprise asking questions. That being the case, I thought it was timely to lay out a few of the facts I am aware of, about the process of dredging and the impact this process could have on Norfolk Island’s inshore reef area.
Background
The view southwards, towards the dredge site
Kingston lagoon and reef, as part of the Australian Marine Parks network has high ecological values. It directly abuts the World Heritage-listed Convict Property of Kingston and Arthur’s Vale, and also holds significant cultural values for the descendants of the Pitcairn Islanders. Together, these areas comprise a unique, globally important site.
The Kingston Pier channel deepening project aims to make access to the historic port of Kingston easier and safer, and presumably this will benefit Norfolk Island’s economy in the process. It involves dredging up to 6,000 m³ of dredge volume, which will be removed from the site and taken to the opposite side of the island and deposited at the Cascade Quarry. To visualise this, think of 2.5 Olympic swimming pools, 2 metres deep, side by side.
The dredge site itself is only metres from arguably the best corals in the lagoonal system; these are corals that have been least affected by the poor water quality following in via the convict-built drainage system of Kingston that goes into Emily Bay at the eastern end of the bays.
Disclaimer
I am certainly not opposed to progress and improved infrastructure and I would prefer to leave a discussion on the necessity for this for others to debate; however, I would point out that since this project was first mooted a few things have changed, including:
our lighterage equipment and how goods are transferred to shore
the use of PTVs (passenger transfer vessels) for cruise ships, especially while there seems to be an increasing number of residents who are not overly keen on these and question how much they add to the economy.
Neither of these things are something I am able to comment on. I am also not in a position to comment on the use of Kingston by our local fishing fleet and their requirements for entering and exiting the water safely. Some catch fish for their livelihoods, while others are keen and/or occasional fishers. Will the dredging make a difference to their access, and will the prolonged closure of the pier to community members be worth the final outcome?
Having clarified the scope of this blog post, I think it is important that all the facts around dredging are spelled out in plain language so we can all understand what is at stake. Moreover, we need to critically examine the need for this improved port infrastructure in order to justify and weigh up the possible consequences for our reef.
A reef under stress
Anyone who follows my posts and this website, will know that for some time now I have been advocating for our reef. It is important to remember that Norfolk Island’s reef has experienced exceptionally high levels of disease. As noted by Page et al. (2023), ‘In December 2020 and April 2021, we observed 60% of surveyed Montiporid coral colonies with signs of disease, a prevalence in line with the most severe coral disease outbreaks recorded to date worldwide.’
In addition to this sad finding, we have report after report further detailing how our reef is suffering as a result of poor water quality flowing onto it.
CSIRO, among many other organisations and researchers, has attributed this poor water quality to several factors, but primarily it is caused by cattle in close proximity to waterways, and poorly sited and maintained private septic systems. I am not going to go into a lot of detail here as I have written about the issues ad nauseam, but here is a short list of some external reports:
Improving the Water Quality of Emily Bay, Norfolk Island, a report by Bligh Tanner
Microbial source tracking of fecal pollution to coral reef lagoons of Norfolk Island, Australia, a report by CSIRO
Norfolk Island water quality assessment. A report from the CSIRO Norfolk Island Water Resource Assessment to the Australian Government
Wastewater Management Strategy, prepared by Norfolk Island Regional Council.
The area closest to the Pier, at the far western end of Slaughter Bay, is arguably one of our most beautiful and healthy spots on the reef. This is where, when I set up my research cameras, I find the most species of fish, a wide variety of corals, and a good population of invertebrates, including sea slugs, nudibranchs and more.
Growing new corals (known as reef recruitment)
As well as the poor health of the reef, our corals are struggling to ‘recruit’. That is, to have new baby corals. During the 2024–2025 summer period, for whatever reason, we had no documented coral recruitment. This means our reef isn’t readily renewing itself. As we lose colonies to disease, they are not necessarily being replaced.
Bleaching
Increasingly, coral reefs around the world are experiencing bleaching events as temperatures gradually increase. Put very simply, a heat-stressed coral, if it is bleached for long enough, can die. If it is for a short period (coral species vary in their response to heat stress), the coral may recover, although it can take quite a while for this to happen. For example, in 2024, I followed one Montipora coral colony from when I first noticed it being bleached on 23 March, to when it finally looked like it had properly recovered seven months later, on 30 October 2024. Bleaching is a sign that the coral is stressed and when corals are stressed, they are more likely to succumb to other stressors. For example, while bleached, parts of this aforementioned coral colony were subject to a disease with a similar progression to Atramentous Necrosis, which I write about here: Combine bacteria, fungi, and maybe a sponge = one toxic mess.
The point I am making is that when you have an already stressed reef, whether it is because of poor water quality or through heat stress, adding further stressors, such as those potentially arising from the dredging process, can be enough to tip them over the edge. And our reef is already showing all the signs of being stressed.
what are the potential issues when dredging close to corals?
Below are listed some of the risks associated with dredging, not all of which may be applicable to Kingston if the project is managed properly.
Direct physical destruction: Reefs inside the footprint are literally removed, fractured or buried by dredge heads and spoil disposal. Dredging has repeatedly led to permanent loss of coral habitat by either directly removing the corals or by burying them (Erftemeijer et al., 2012).
Chronic turbidity (cloudiness of the water caused by silt particles) and consequential light reduction: Dredging creates persistent sediment plumes. The closer the marine habitat is to the dredge site, the worse the effect will be (Fisher et al., 2015). Suspended sediments reduce light, which is needed by the symbiotic ‘algae’ that live inside corals, known as zooxanthellae. These photosynthesise to produce food for the coral. With reduced light this can depress photosynthesis, growth and calcification, and also reduce the depth range in which corals can live (Morgan et al., 2020).
Sediments smothering the corals: Fine sediments will settle out and then repeatedly re-suspend, causing partial and complete burial of colonies (as mentioned above), and can cause tissue necrosis and death (Erftemeijer et al., 2012). The sensitivity of corals to sediments is different for different coral types. Branching and plating corals are generally more vulnerable than massive (boulder) corals (Erftemeijer et al., 2012).
Reduced recruitment: Sediment films on the benthos (the organisms that live on or in, or near the bottom of the body of water) inhibit larval settlement and the survival of newly settled coral recruits. Experimentally, heavy sediment cover can cut recruitment by an order of magnitude (Erftemeijer et al., 2012). That means that even if some adult corals can hang on, recovery of the reef can stall.
Disease and sub-lethal stress: At several sites, dredging plumes have been linked to increased coral disease and ‘compromised health’ (lesions, partial mortality) (Pollock et al., 2014). Sediment trapped in the corals’ mucus layers can fuel bacterial growth and hypoxia (caused by a lack of oxygen) on the tissue surface (Erftemeijer et al., 2012).
Mobilisation of contaminants: Where sediments are contaminated (metals, hydrocarbons, nutrients, acid sulphate material), dredging can re-expose and redistribute these over reefs, adding additional stress (McCook et al., 2015).
Hydrodynamic and geomorphic changes: Deepened channels and spoil mounds can alter local currents and wave energy, shifting long-term patterns of sediment transport and erosion/accretion on adjacent reefs and Pier walls, such as the recently repaired revetment at Kingston (Fisher et al., 2015).
The key point to make here is that impacts almost never stop at the edge of the dredge footprint or within the neat lines shown in an Environmental Impact Statement. Plumes and deposition fields are messy, weather-driven and hard to constrain. And anyone who has livde on Norfolk Island for even a short while will understand something of the variability of the currents and seas along our southern coastline.
The Kingston Pier channel project
With the above background in mind and for the sake of completeness, here are a few documents relevant to the current Kingston Pier channel project, with my apologies for the reading:
Kingston Pier channel project Fact Sheet (16 January 2020)
The Public Environment Report Guidelines for the Kingston Pier channel project (May 2022)
Draft Kingston Pier Channel Construction Project, Public Environment Report (17 January 2023)
My response to the above Public Environment Report (24 March 2023)
The amended Kingston Pier Channel Construction Project, Public Environment Report (2 May 2023).
At the time I wrote my response, I had been studying the bays as a private citizen for about three years. Since then, a few things have changed, including the numbers of new species that have been identified inside the lagoons (it was 11 then, it now stands at 24), and the fact that I am now undertaking a PhD in Marine Science. Yet what I said in 2023 is still true, or has become even more pertinent since then. I would add that we are still discovering new things about this ecosystem. For example, there is a small, as-yet-undescribed Eviota spp (see image below) that is thought to be new to science and possibly endemic to Norfolk Island.
Unidentified Eviota spp.
The final document for this project is this:
The Notification of Approval Decision for the Kingston Pier channel project (7 April 2025)
It is this document that outlines the project details and how it will be undertaken. I will now go through it and explain what it all means.
The Approval
The federal EPBC approval for the Kingston Pier channel project does put some hard limits around the activity. For example, it:
confines dredging to the defined Kingston Pier ‘disturbance footprint’ and prohibits works outside that mapped area
caps the total dredge volume at 6,000 m³
prohibits dredging during the identified coral spawning period
restricts spoil disposal to the existing Cascade Quarry, rather than allowing it to be disposed of at sea or at a new site(s) on land.
On paper, that is meant to contain both the physical footprint of excavation and the location of spoil.
The approval is also conditional on a suite of management plans being prepared, approved and implemented before dredging starts, as follows:
Construction Environmental Management Plan (CEMP) – this must set out ‘SMART’ (specific, measurable, achievable, relevant, time-bound) commitments for construction, along with the monitoring, trigger values and corrective actions that will supposedly prevent or minimise environmental harm.
Kingston Pier Underwater Archaeological Management Plan (KPUAMP) – this plan sits alongside the environmental documents but is focused on protecting underwater cultural heritage, including submerged archaeological deposits in the dredged sediment, the HMS Sirius wreck, and Commonwealth heritage values at Cascade Reserve. It must be prepared by a ‘suitably qualified underwater archaeologist’, and align with the national guidelines Assessing and Managing Impacts to Protected Underwater Cultural Heritage in Australian Waters (2024). As above, it must include ‘SMART’, evidence-based heritage outcomes, risk assessment and mitigation measures, ‘unexpected finds’ protocols, and a monitoring programme with performance indicators, trigger values and defined corrective actions.
Marine Incident Management Plan – this covers incident response for marine impacts such as sedimentation events, vessel strike on protected species, underwater noise, and the introduction or spread of marine pests.
Water Quality Management Plan (WQMP) – this is the central document for sediment and plume control. It must include sedimentation and plume modelling, an ‘adaptive’ water-quality management framework, a monitoring programme, numerical trigger values for water quality, and a linked coral management plan that spells out how those triggers will be used to protect coral communities.
Across these documents, the conditions repeatedly state that the plans must be designed and implemented so as to ‘prevent any avoidable harm to protected matters’, and ‘mitigate unavoidable and accidental harm’ in relation to listed species, listed ecological communities and National Heritage / World Heritage values associated with Kingston and the surrounding reef.
Finally, the approval allows the proponent to revise these management plans over time without seeking a new Ministerial decision, provided they consider that the changes will not lead to any ‘new or increased impact’ on protected matters. Revised plans must be submitted to the Department for review, but unless the Department actively objects, the updated versions – including any altered trigger values or monitoring designs – simply replace the originals.
Where there are corals, there are fish, western Slaughter Bay
What best-practice science says about dredging thresholds
When you line the Kingston approval up against the experimental work on corals and sediment, a few points stand out very clearly.
The most comprehensive synthesis to date – a global systematic review of experimental studies on sediment exposure – shows that very small amounts of settled sediment can do real damage. Adult corals start to show tissue loss and necrosis at deposited loads of around 5 mg of sediment per square centimetre per day, and larval settlement is inhibited at roughly 1–2 mg cm⁻² day⁻¹. Once you get beyond those levels, especially over multiple days, burial and tissue death become increasingly likely (Tuttle & Donahue, 2022).
By comparison, suspended sediment in the water column (the ‘cloudiness’ we see) generally takes an order of magnitude longer to kill corals outright than an equivalent dose of settled material (Tuttle & Donahue, 2022). It still causes stress – reduced photosynthesis, excess mucus production, energy diversion – but it is the deposited layer that suffocates coral tissue fastest.
Dredging rarely produces sediment alone; it produces turbid plumes that block light. As already mentioned, corals rely on light for their symbiotic algae (zooxanthellae) to photosynthesise. Experimental work where corals were held under controlled turbidity shows that weeks of elevated suspended sediment and reduced light push corals towards bleaching and partial mortality, particularly when daily light levels fall to only a few mol photons per square metre per day (Jones et al., 2020; Bessell-Browne et al., 2017). At that point, corals are running an energy deficit: they can survive for a while, but the safety margin is gone. Interestingly, there are large numbers of pocilloporid corals (P. damicornis) in the area immediately to the east of the Pier, and this was found to be the most sensitive species to reduced light (Jones et a., 2020).
P. damicornis
Bessell-Brown et al. state, ‘Recent monitoring studies during dredging campaigns on a shallow tropical reef, have shown that underwater light levels very close (~500 m away) (my emphasis) from a working dredge routinely fall below this value over 30 d periods, but rarely during the pre-dredging baseline phase.’
Sediment and light stress do not act in isolation. During the 2013–2015 PortMiami channel deepening, tagged colonies on nearby reefs experienced extensive partial and complete burial from dredge plumes, followed by elevated disease and mortality compared with reference sites (Miller et al., 2016). That pattern – sediment damage followed by disease outbreaks – is now recognised as a real risk, especially on already stressed reefs.
Taken together, the evidence base is blunt:
corals are sensitive to quite low levels of sediment and light reduction, especially over weeks rather than days
deposition, not just water cloudiness, is the parameter that matters most for rapid, acute coral mortality
dredge-related plumes and deposition fields are messy and often much larger than predicted, which means that even reefs technically ‘outside the footprint’ can end up in the firing line.
Let’s step through what we have in the approval and what we need
While we have the Approval document, if this project is to go ahead, there are some things we need to ensure will happen.
1. Clear limits for sediment and light at the reef
What’s needed
For a high-value reef, best practice is to set clear numerical limits for how much extra sediment and how much loss of light the corals are allowed to experience – over days and weeks – based on published science. Those limits should be written into the approval itself and tied to automatic ‘stop work’ rules if they are breached.
What we have
The Kingston approval talks about ‘trigger values’ and ‘performance indicators’ in the Water Quality Management Plan and coral management plan, but it does not set any numbers in the approval. All the detail – how much sediment is too much, how dark is too dark, for how long – is pushed off into a future plan written by the proponent.
Why that matters
The most critical settings for coral survival are not fixed up-front. They can be set later, out of public view, and there is a real risk they end up too loose to be genuinely protective.
2. Measuring what actually kills corals
What’s needed
The thing that kills corals fastest is settled sediment – the stuff that lands and stays on the coral surface – not just how cloudy the water looks. Best practice is to measure deposition directly at the reef (how many milligrams per square centimetre per day), not rely only on turbidity sensors further away.
What we have
The approval requires water-quality monitoring and refers to ‘sedimentation’, but it does not spell out that actual deposition rates at the coral reef must be measured. The ‘how’ is again left to the Water Quality Management Plan.
Why that matters
If you only track water cloudiness and don’t measure how much sediment is settling on the corals themselves, you can miss the most damaging part of the impact.
3. Keeping dredging far enough away from the reef
What’s needed
Elsewhere, big dredging projects define zones of high and moderate impact based on how far plumes and sediment are expected to travel, and then make sure sensitive reefs sit outside those high-risk zones. That means setting a minimum stand-off distance between the dredge and the corals, based on modelling and past experience.
What we have
The Kingston approval limits where dredging and spoil disposal can occur – it says ‘do not dredge outside the Kingston Pier disturbance footprint’ and ‘do not place spoil outside the Cascade Quarry disturbance footprint’ – but it never specifies any buffer distance between the dredge and the nearest coral communities.
Why that matters
Plumes and deposited sediment don’t stop neatly at the edge of a drawn box. Without an explicit stand-off distance, there is nothing in the approval itself that guarantees the most intact coral areas are actually kept out of harm’s way.
4. Changing the rules later
What’s needed
If thresholds, monitoring or mitigation measures are going to be weakened, that should trigger fresh scrutiny and a new decision, because that’s exactly how protections get watered down over time.
What we have
Under this approval, the proponent is allowed to revise the management plans, including the detailed trigger values and corrective actions, without a new Ministerial decision, as long as they say the changes won’t cause ‘new or increased impact’. The Department can object, but if it doesn’t, the new version simply replaces the old one.
Why that matters
On day one the plans might look relatively strong. But the approval leaves a pathway for gradual weakening of protections over time, with most of the real decisions happening in management plans that sit behind the scenes rather than in the approval the public can see.
Conclusion
In the end, this is not a story about being ‘for’ or ‘against’ dredging. There are perfectly valid reasons to want a safer, more reliable channel – for freight, medical evacuations, and the basic functioning of an isolated island community. But we also have to be honest about the trade-offs. We are talking about adding a known, well-documented stressor right next to a reef that is already showing signs of strain from poor water quality, warming seas and recurring algal and cyanobacterial blooms. That is exactly the kind of situation where ‘just a bit more stress’ can be enough to tip a system over the edge.
The EPBC approval puts some limits around the project and requires a suite of plans that, on paper, sound reassuring. What it does not yet do is lock in the numbers that really matter – how much sediment, how much light loss, for how long – or guarantee that those limits will be measured at the reef itself and enforced with hard stop-work rules. Those details sit in management plans still to be written, and can be revised later with relatively little public visibility. That is where risk creeps in.
If this project goes ahead, we need to go into it with our eyes wide open. That means asking clear, specific questions: What are the exact sediment and light thresholds that will trigger a shutdown? How will settled sediment on the corals themselves be measured? What stand-off distance will actually keep the healthiest parts of the reef out of the plume? And what is the process if monitoring shows things are going wrong?
Norfolk’s reef is small, irreplaceable and still revealing new species and ecological relationships. Once lost, it does not come back on any human timescale. Whatever decision is made about the channel, it should be made in full view of the community, with the best available science on the table – not on blind faith that ‘plans’ written later will quietly take care of it.
References
Bessell-Browne, P., Negri, A. P., Fisher, R., Clode, P. L., & Jones, R. (2017). Impacts of light limitation on corals and crustose coralline algae. Scientific Reports, 7(1), Article 11553. https://doi.org/10.1038/s41598-017-11783-z
Erftemeijer, P. L. A., Riegl, B., Hoeksema, B. W., & Todd, P. A. (2012). Environmental impacts of dredging and other sediment disturbances on corals: A review. Marine Pollution Bulletin, 64(9), 1737–1765. https://doi.org/10.1016/j.marpolbul.2012.05.008
Fisher, R., Stark, C., Ridd, P., & Jones, R. (2015). Spatial Patterns in Water Quality Changes during Dredging in Tropical Environments. PloS One, 10(12), e0143309. https://doi.org/10.1371/journal.pone.0143309
Jones, R., Giofre, N., Luter, H. M., Neoh, T. L., Fisher, R., & Duckworth, A. (2020). Responses of corals to chronic turbidity. Scientific Reports, 10(1), Article 4762. https://doi.org/10.1038/s41598-020-61712-w
McCook, L.J.; Schaffelke, B.; Apte, S.C.; Brinkman, R.; Brodie, J.; Erftemeijer, P.; Eyre, B.; Hoogerwerf, F.; Irvine, I.; Jones, R.; King, B.; Marsh, H.; Masini, R.; Morton, R.; Pitcher, R.; Rasheed, M.; Sheaves, M.; Symonds, A.; Warne, M.St.J. 2015, Synthesis of current knowledge of the biophysical impacts of dredging and disposal on the Great Barrier Reef: Report of an Independent Panel of Experts, Great Barrier Reef Marine Park Authority, Townsville.
Miller, M. W., Karazsia, J., Groves, C. E., Griffin, S., Moore, T., Wilber, P., & Gregg, K. (2016). Detecting sedimentation impacts to coral reefs resulting from dredging the Port of Miami, Florida USA. PeerJ (San Francisco, CA), 4, e2711. https://doi.org/10.7717/peerj.2711
Morgan, K. M., Moynihan, M. A., Sanwlani, N., & Switzer, A. D. (2020). Light Limitation and Depth-Variable Sedimentation Drives Vertical Reef Compression on Turbid Coral Reefs. Frontiers in Marine Science, 7. https://doi.org/10.3389/fmars.2020.571256
Pollock, F. J., Lamb, J. B., Field, S. N., Heron, S. F., Schaffelke, B., Shedrawi, G., Bourne, D. G., & Willis, B. L. (2014). Sediment and Turbidity Associated with Offshore Dredging Increase Coral Disease Prevalence on Nearby Reefs. PloS One, 9(7), e102498. https://doi.org/10.1371/journal.pone.0102498
Tuttle, L. J., & Donahue, M. J. (2022). Effects of sediment exposure on corals: a systematic review of experimental studies. Environmental Evidence, 11(1), Article 4. https://doi.org/10.1186/s13750-022-00256-0