Flood defences: what's Bristol's long

The council is searching for an extra £100 million to fund future flood defences to protect low-lying areas of the city. While residents call for greater action, the Cable looks across the North Sea to Rotterdam for inspiration.

Roseanna Sharp, says that more needs to be done to protect Sea Mills, the Bristol suburb where she lives, from rising tides (Photo: David Griffiths)

It’s a still summer evening and the waters of the tidal River Trym are fairly low – about four metres deep – leaving parts of the silty, brown river bed exposed and sparkling.

“We will often sit out on the grass to watch the sunset. It’s such a privilege to be able to look out over the river. It’s a really big part of our life,” says Eva Whittaker, whose family’s house sits on the bank of the river, just 200m before it merges with the much larger Avon.

Neighbours are quietly chatting on the pavement, and a train occasionally passes through the station at the end of the street. It’s an idyllic neighbourhood, but a metal barrier blocking off Whittaker’s driveway from the main road signals trouble.

Sea Mills, an otherwise cosy suburb in the northwest of Bristol, is particularly vulnerable to flooding during high tide events, and according to the council, the threat to the neighbourhood is going to get worse.

In recent years, Bristol’s flood defences have started to be tested, if they exist at all. In 2012, around 25 properties flooded following a heavy rainfall event. Two years later, the first emergency flood barrier was deployed following a storm surge which partially blocked the Portway, the road that runs beneath the Clifton Suspension Bridge.

In 2020, multiple roads were submerged and Junction Lock at Cumberland Basin, which protects the floating harbour from high tide events, was breached.

As the council scrambles to locate £100 million to plug a shortfall in funds for future flood defences, the Cable investigates how vulnerable Bristol is to flooding – and, with Rotterdam-based journalist Zuza Nazaruk, whether we can learn from projects being trialled abroad.

The lowdown

The problem: Bristol is particularly vulnerable to flood events, and models predict these are likely to get much worse. Despite this, significantly more funding is needed and some residents in flood risk zones feel ill-informed about the proposals to future-proof the city.

The solution: Coastal cities around the world can act as a blue-print to inspire Bristol’s plans. In Rotterdam, community initiatives and public-private partnerships have both been embraced. But there are lessons to be learned about how some of these projects have failed to benefit the city’s more marginalised communities.

Roseanna Sharp, 71, who lives next door to Whittaker, says more needs to be done to protect Sea Mills from rising tides. “I go to Severn Beach and there are flood defences around there, but nothing here,” she says. “It’s almost like we’ve been left behind.”

It’s not just homes that are under threat, she says, but a frequently used through-road and Sea Mills train station. A community allotment could also be at risk.

In the 2020 flood, the River Trym swelled to nearly nine metres and overtopped the river bank. Sharp watched as Whittaker’s property, which was then occupied by different residents, was flooded.

“It came all the way up the driveway and broke through into the garage. You couldn’t park on the road and getting in and out was very difficult,” Whittaker says, having been informed about the flood by the previous owner.

Sharp’s house narrowly escaped the rising waters. “Has it hit my house yet?” she can remember shouting out the upstairs window to an Environment Agency worker down on the street below. “It’s a worry for a lot of people. I don’t know why they don’t do something,” she says.

Since the flood, residents say there has been little communication from Bristol City Council about future flood defences. An investigation carried out by the local authority found flooding in Sea Mills will “inevitably” worsen due to climate change, but that the risks were “poorly understood” compared with other areas in the city centre.

Bristol City Council says that this historic flood event was caused by high spring tides – the highest on record for the city – combined with a storm surge. The latest climate models indicate that flood events like this are only going to increase.

Today, around 1,200 properties are at risk of severe flooding from the tidal River Avon, which presents the biggest risk to Bristol. Significant parts of the city centre, along with Avonmouth, are currently left undefended.

This number of at-risk properties is expected to rise to 4,500 by the end of the century unless action is taken, according to a council report published in May.

When surface flooding from heavy rain is taken into account, which carries the additional risk of overwhelming the already stretched sewage system, the number of at-risk properties increases by more than 3,000.

“In a city like Bristol the flood risk from tides and rivers is really serious. There is no development allowed near the harbour now with ground-floor accommodation. That’s why you have raised first floors and under-croft parking,” says Martin Fodor, the Green councillor for Redland ward and chair of Bristol City Council’s Communities Scrutiny Commission.

“New student accommodation in the city centre, above the path of the River Frome, has evacuation plans, almost like a landing jetty, to remove the hundreds of occupants in the event of a significant flood event.”

In 2020, the McKinsey Global Institute, a think tank focusing on business and economics research, collaborated with Bristol City Council to explore future flooding scenarios for the city. It found the current risk is modest, with life returning to normal within a matter of days or a few weeks after a flood event.

But they warned of a dramatic escalation in likely impacts if sufficient flood defences are not put in place. In 2065, a flood event with a probability of 0.5% could render Temple Meads inaccessible, block off a third of city-centre roads and flood a major substation in Avonmouth that powers around 20 to 30% of Bristol.

In total, this could cause roughly between £400 million to £2 billion of economic damage, including knock-on effects to the local economy.

It’s clear Bristol’s current defences are not going to be sufficient, with key infrastructure and energy systems potentially at risk before the turn of the century. So, can Bristol learn from other cities that are already facing this level of threat today?

Rotterdam and Bristol share important similarities. As historic port cities, the most vulnerable areas to flooding are situated near the Nieuwe Maas River and River Avon, respectively. Both rivers then make a short onward journey to the sea, increasing the risk of tidal flooding.

“The Dutch have lived with the water since the country was formed,” says Rotterdam-based journalist Zuza Nazaruk. “But the mayor has made it clear that it wouldn’t be possible to get everyone out of the area in a significant flood.”

Last year, Nazaruk worked on an investigation for cross-border newsroom ‘Unbias the News’ which examined how cities are adapting to sea-level around the world.

Her reporting exposed an irony in Rotterdam’s climate mitigation efforts. For starters, the city’s harbour, which is heavily protected against future sea-level rise, is home to five oil refineries and a large coal-fired power plant.

The port produces 90% of Rotterdam’s emissions. The money made from this industrial area is then funnelled back into financing climate adaptation projects in the city.

Like Rotterdam, Bristol is well-known as a city whose wealth was founded on its proximity to the river. During the 17th and 18th centuries, the Avon acted as a key link between the city and the global trafficking of enslaved people.

In May 1804, three years before the abolition of the slave trade, merchants in Bristol decided to build the city’s iconic floating harbour after becoming fed up with the number of ships becoming stranded in thick mud during low tide.

Today, this feat of engineering remains one of the city’s key defences to flooding, cutting off the harbourside from the tidal impacts of the Avon.

The threat of sea level rise is more immediate to Rotterdamers. One-third of the Netherlands – literally translated as “lower countries” – lies below sea level, with this figure climbing to 90% in Rotterdam.

In January last year, coastal flooding overwhelmed the city, blocking off roads and causing widespread travel disruption. In other areas, cycling and walking paths were closed in fear they would be submerged. But the city’s well-designed flood defences prevented any significant impacts.

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Disaster forced the country’s government into action. In 1953, a storm surge in the North Sea killed 1,835 people in the Netherlands after defences across the coastline were breached.

Just one year later, a national programme called Delta Works was launched to construct coastal defences, but it wasn’t until the late 90s until a storm surge barrier, also known as the Maeslant barrier, was built to fully protect the port.

“The dikes and Maeslant barrier are the backbone of the city’s flood defences,” says Nazaruk, adding that the barrier is capable of defending the city until 2070. “They really put a lot of resources into making Rotterdam a fortress.”

In Bristol, things are not so simple.

“A barrage probably creates terrible pollution and damage to rare ecosystems on the mudflats that are of international or national significance,” Fodor says. “There will always be proposals to put a barrage across the Avon, but it’s usually from people who are thinking about real estate value, with nice views of a water area to look over, not protecting biodiversity.”

Nicola Beech, Bristol’s cabinet member with responsibility for strategic planning, resilience and floods, agrees that plans for a barrage are not feasible. “Lots of people have these European dreams of creating a riviera,” says Beech, a Labour councillor for St George central. “First, it would be hugely expensive. I think it would blow the cost of the phase one defences out of the window.”

“Second, the water is multidirectional. There is a real danger that water would get trapped in the system.

“Third, the area around the Avon is a Site of Special Scientific Interest which has hugely important flora and fauna. It would fundamentally change the river system that has been there for thousands of years.”

Nazaruk says though that inspiration can be taken from Rotterdam that goes beyond a tidal barrage. Rather, the risks presented to the city have inspired a new generation of water-based innovation.

Public plazas with gardens and basketball courts have been created, which fill up with water during heavy rainfall, acting like sponges to soak up the city’s excess water.

Down by the water’s edge, some communities are actively embracing the rising water levels. Floating buildings, and even the world’s first floating farm, are all seen to be a huge success and have become an integral part of the city’s climate resilient strategy.

Visitors to the city can even book their own ‘Wikkelboats’ – small houseboats made of corrugated, waterproofed cardboard. Founder Sander Waterval says 10,000 guests have stayed in his floating houses in the last year. “They can definitely help to showcase how awesome living on water can be,” he says. “You can experience the water in a totally different way”.

In other areas, Nazaruk says communities are taking matters in their own hands, albeit in small ways.

Neighbours come together to take part in an activity called ‘tile flipping’, which involves removing pavement tiles and filling the exposed soil with plants to allow rainwater to soak into the soil below.

“It’s such a Dutch thing to do,” she says.

Residents in Bristol are overwhelmingly in favour of greater investment in adaptive flood defences, but what these measures will be or what they will look like is less clear.

More than 80% of responses to a public consultation launched in October 2020 were in favour of further defence measures, such as submersible riverside paths, glass panelling and terracing like that seen alongside London’s South Bank.

But concerns were raised about overdevelopment on floodplains and the maintenance costs of the measures. The vast majority of respondents were from Hotwells & Harbourside, followed by Central ward, which are both at significant risk of future flooding.

The Department for Environment, Food and Rural Affairs (Defra) is set to spend £200 million on flood defence programmes across the UK before 2027, including specific projects in 25 vulnerable areas that will receive an average of £6 million each. But this won’t be nearly enough to cover Bristol’s flood defence plans.

Nazaruk says an average of €1.25 billion (£1.1 billion) a year has been set aside until 2032 for maintaining and building flood defences in the Netherlands. That blows Bristol’s budget out of the water.

Beech admits funding is a challenge. “The current cost to deliver the first phase of the strategy for the next 10 years sits at £216 million. We are at 52% of that from a funding perspective, so we’re about £100 million short.”

This is further complicated by a lack of funding for greener, more visually creative flood defences. Beech says the Environment Agency just focuses on defences that protect people and property.

“You have the cost to make it safe, which would look bloody awful, and then you have the cost to make it a really lovely public space, which the city embraces. What we want to do is create this green corridor which covers the entire city. Generations of Bristolians will be grateful for that.”

Some are concerned that funding pots – like the Community Infrastructure Levy (CIL), a charge developers pay to local authorities – might be diverted away from communities in order to protect new developments against flooding.

“My concern is that CIL, paid to the council by most major developments, could end up going towards managing flood risk, by making sites themselves safe for development, or to deal with the impacts of development itself,” Fodor says. “That could mean that there is nothing left for meeting unmet needs for improvements for the community already there”.

The council says some CIL funding has been earmarked for flooding projects, but that its primary aim is to protect existing homes, businesses and communities from flooding, not just to make sites safe for development.

Drawing money from public-private partnerships could help to alleviate some pressure on public funds, and some local innovators are already making proposals about how they could be part of the solution.

Earlier this year, keen sailor and entrepreneur Kev Draper criticised the council after it opposed plans to build floating homes in the harbour.

“From a flood defence perspective, floating homes are fantastic,” he tells the Cable. “It will take some radical thinking though. The Germans are ahead of us. The Dutch are way ahead of us.”

As Managing Director of Float8, a Bristol-based company focusing on urban blue-space development, Draper has already drawn up plans to transform the Avon. “Opposite SS Great Britain there is a long stretch of waterway lying barren. We’ve produced CGI images to demonstrate what we could do, with floating log cabins.”

“The beauty about our idea is that selling floating homes as a joint venture would give the council money,” Draper says, adding that this money could be spent on other flood defences around the city. “Let’s say we sold a two-bedroom floating home for £375,000, we could give the council £50,000. It could be more but it depends how much it costs us.”

But the council’s official stance has not been supportive. “I’d love to see it happen in Bristol, my home town, but we’ve had the hardest time with them,” Draper says.

Beech says her priority is keeping people out of harm’s way. “Personally, I don’t oppose the use of houseboats in the long-term, but there is always a balance to be struck. Right now, my priority is to make sure people are safe,” she says.

Bristol City Council said officers and a now-former councillor met with Mr Draper some years ago to hear his ideas. “As explained on a number of occasions, there are no plans to introduce floating houses on the harbour,” a spokesperson said.

“We are in the process of introducing a number of improvements to the harbour area as part of the Harbour Review and investing heavily in harbour infrastructure. Meanwhile, back on dry land, Bristol built 2,563 new homes in 2021/22, exceeding the Mayor’s ambitious target, including more new affordable homes than for any year in the last 12.”

In Rotterdam, Nazaruk says the growth of houseboats in the city has been divisive. “Floating houses are really interesting, but they’re not for everyday people,” she says.

“In Rotterdam South, one of the poorest districts in the city, there was a neighbourhood of floating villas created,” she says. “I interviewed people who had lived in the neighbourhood for years and their windows looked out over the floating houses. They said, ‘These measures are not for us. We cannot afford this’.”

Some of the floating houses were being sold for €505,000, Nazaruk says.

“If we see this as an anti-flood measure, how many people are you going to help? The real challenge is how we can future-proof the existing housing stock.”

Bristol’s flood defence works are still firmly in the planning stage, which is a concern for those living in areas of the city most under threat, but for others it means residents still have time to have their say in the decision-making.

“Invariably, it will involve having to raise up the river bank,” Beech says. “How that will look in detail, we don’t know yet. If your priority is the protection of people and property, then unfortunately reed beds and other nature-based solutions would just get wiped out. That’s the tough reality of the River Avon.”

For residents of Sea Mills, there is an eagerness for answers. “Can you come back and let us know once you’ve found out what the plan is?” one asks.

Bristol City Council says modelling in the Sea Mills area has improved since the 2020 floods, but that risk mitigation measures are being investigated.

This is reassuring news for residents who have made the riverbanks of Bristol’s waterways their home. But they hope defences will be built in time. “I’d love to stay here forever. It would be amazing if we could protect it,” Whittaker says.

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Read more on: bristol city council, environment

Home » Future of Cities » Bristol’s flood defences are being pushed to their limit. What is the city’s long-term plan, and will it be enough?

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