My dissertation project origins

Having lived and worked in Brighton Marina for over five years, I had seen at first hand the problems of silting-up of a marina. Accumulation of silt is a problem that almost every port, harbour and marina the world over suffers from.
When the high energy ocean waters enter the calm sheltered safety of a port, the drop in energy levels of the water means that it can no longer carry the same amount of suspended sediment, and therefore deposits its suspended load on to the bed of the port.

It’s important to differentiate here between dissolved and suspended. Content that is dissolved in the sea water has undergone a chemical reaction and will remain dissolved regardless of the energy levels of the water. Suspended material however is merely carried by the water and will be deposited as soon as energy levels drop.
In the few years since moving on to my boat, the silting at Brighton Marina has become progressively worse with access to the marina becoming more and more restricted as the attempts to dredge the fairways and berths fails to keep pace with the sediment build-up.

Currently the standard solution to sediment build-up is to scoop it out using a large excavator (backhoe dredging) and dump it in to a specialised (split) barge, that then transports it out to sea and drops it somewhere they think won’t matter.

This method of sediment management raises a number of issues:-
I} discharge of sea toilets, engine grease, litter, and antifoul are all deposits that are particularly concentrated in marinas and ports. None of these contaminants are positive for the marine environment, and in their often-concentrated forms in port silts can be devastating to marine life.
Ii}as silt builds up, anoxic (low or no oxygen present) mud is produced as there is no penetration of the top few centimetres of the mud. This dark, stinking mud is almost devoid of life, but when disturbed (during the dredging process) quantities of methane can be released; a gas that can be over twenty times more effective as a greenhouse gas than CO2.
Iii} a typical split barge (a vessel that is amazing in itself, as it literally splits in two and allows its load to fall down through the gap), can carry up to 600 tonnes of silt in a single load. When dropped on to the sea bed, away from the marina, this sudden and dramatic inundation of silt can be catastrophic to filter feeders and benthic (bottom dwelling) species.
In Brighton the above considerations must be viewed whilst remembering that the marina lies at the western edge of a marina conservation zone, and that all the silt being removed from Brighton marina is then being dumped in to what should be a protected and conserved area.

Backhoe dredging is not a cheap process, with a typical annual bill of £300,000 to £500,000 not being unrealistic, and at these levels of expenditure silt is still accumulating quicker than it is being removed.
With my personal experience of trying to get my own yacht in and out of the marina, with her 1.8 metre draft, and the knowledge I was gaining during my University of Brighton Earth & Ocean Science Bsc (Hons) course, I felt that there had to be a better solution?
I began to read research papers on sediment management, I learnt about the intricacies of suspension times, currents, coastal littoral cells, and particles sizes. With this growing knowledge and interest in how sediment built up, I approached the marina management at Premier Marinas Brighton to discuss a potential dissertation project for my bachelor’s degree.

Brighton Marina, an analog for climate change.

Brighton Marina, inner harbour water level, February 2018. S. Hall ©

The Marina’s birth

Built in the 1970s, Brighton Marina came to typify for many the twentieth century’s love of concrete and disregard for the natural world. Perched on the south coast of England in an area dominated by towering chalk cliffs, the marina which is entirely artificial juts out into the sea like a monument to the human race’s engineering achievements. Or an ugly boil on the coastline, depending on your point of view.

With a chequered financial history, and varying objectives over its lifetime, the marina is seen by many as more like a housing estate than a centre of sailing excellence. Recent high-rise developments and encroachment into the waterways of the outer harbour of the marina is a reminder of the fickle financial market we all live in, with the planned multi-million-pound residential development postponed. Or maybe cancelled?

A changing world

With this twentieth century vision of our environment dictating the structure and form of the marina, the growing twenty-first century awareness of climate change and the anthropogenic impact on the world is slowly starting to reveal a worrying future for all of us, not just those in low-lying distant lands. The universal opinion of those in the know is that climate change (we can also call it global warming if we are thinking on a global scale) is happening. The only question is how awful it will be before the rest of us wake up to the danger.

Melting ice sheets in Greenland and Antarctica, caused by average global temperatures creeping up, is causing the volume of water in our oceans to increase. These rising temperatures are also causing the water in the oceans to expand (a process called ‘thermal expansion’), so raising sea levels even further. These effects are just two of the myriad of effects changing global environments. We could also go into detail about ocean acidification, albedo positive feedback loops, terrifying perma-frost releases of methane, and increased water vapour amplifying greenhouse effects, but that would simply ‘muddy’ the proverbial waters.

Depending on which scenario is chosen (i.e. how quickly we as a species get off our arse and do something about the problem), predictions for sea level rise vary from 1 metre to over 10 metres by the end of this century. Which figure is almost immaterial, the key point is that the sea is getting higher and we need to start to worry about it. In this respect, Brighton Marina is a perfect example of what we have done, what we need to do, and how quickly we need to do it.

One hour from disaster

On a perfectly ordinary Sunday in mid-February 2018, Brighton Marina residents, shops, and visitors came within an hour of widespread flooding. This wasn’t due to the rise in sea level, storm damage or any act of God, but simply technical failure of a single piece of equipment.

Most of the Marina is built below the high-water mark, meaning that at some point each month the promenade within the Marina is all that stands between the users of the Marina and the English Channels. On the 18th of February the lock gates in the marina malfunctioned, and suddenly the defences against the encroaching tides had been breached. Luckily the problem was circumvented, and the defences were reinstated before any damage had been caused. Whether the failure was due to human error, poor maintenance or a lack of investment, the fact remains the marina came within 60 cm of major flooding.

In the same way that Brighton Marina is ready for the challenges of today, rather than tomorrow; so we can ask if society generally is falling into the same trap of building for today, rather than planning for tomorrow?

What does this mean for the future?

Does the fault lie in the original design not anticipating future sea level changes?

Does the fault lie in the quality of maintenance within the marina?

Does the fault lie in our arrogant assumption that we are masters of our environment?

Perhaps the answer, at least in part, is yes to all three. In a capitalist society the market is king, and profits dictate behaviour, so the marina will maintain its equipment and defences in such a way that allows the companies involved to make a profit for its shareholders. In the same way countries, companies and individuals will continue to consume without regard to their environment while it is economically viable to do so. The problem is the planet does have a balance sheet. It doesn’t directly impact companies profit and loss, and consequences are often borne by people, animals, and physically remote ecosystems.

How do we change this inequity in the system?

Until polluters are charged (whether that be emissions from power stations, plastics pumped in to our oceans, or chemicals on our fields destroying any organism seen as a threat, to just name a few), the planet as a whole will have to continue to pick up the tab. It will pay a high price for our shiny new cars, our gadgets, and our consumption-driven lifestyles. At some point our credit with mother nature will run out, and we as a species we will be held to account. Many think it is already too late, the question now is not if it will cost us, but just how much we will have to pay for our arrogance.