Flood management in the future means accepting that flooding will happen and putting measures in place for quick recovery.
More from: Facing Down the Floods | Managed Reponse
Flood management is heading into a new phase. Designing for resilience and adaptation has become the norm but now the word on everyone’s lips in the flooding field is “acceptance”. The next 50 to 100 years are going to be about learning to live with rising waters in a changing climate.
That means general acceptance from public and politicians that floods will happen and putting in place measures to allow quick recovery.
Stark future on the coast
On the coast there is a starker future for people in some communities, who will have to accept that their homes will disappear under rising seas.
As Environment Agency chief executive Sir James Bevan said in a speech in March: “On the coast, while we will want to hold the line against erosion wherever possible, affordable and desirable, we have to recognise that in places it won’t be.”
The question that has to be asked, he said, is: “Do we want to defend every inhabited location or should we consider permanently moving some communities which are at the highest risk?”
The problems of England’s crumbling east coast are well known but it is in west Wales where Britain’s first climate refugees – the people having to get to grips with acceptance right now – are facing the realities of a predicted 1m rise in sea levels over the next century.
The proportion of people who accept they are at risk from flooding is not as high as we think it ought to be
The village of Fairbourne in Gwynedd, on the estuary of the river Mawdach, has only decades left before it will be under the waves, according to the most thorough technical projections, and the community has been told it needs to move out over the next 40 years.
“Fairbourne is a community at risk from various sources – coastal storms, rising sea levels, a river that carries mountain run off and a high groundwater table,” says Gwynedd Council senior project manager, flood and coastal erosion risk management Lisa Goodier. “The village can be defended sustainably for the next 40 years but from 2045 it will have to be decommissioned and from 2055 it will not be possible to defend.”
Conversations are now underway as to how to manage moving an entire 800-plus community – and what happens at Fairbourne is likely to set the pattern for other villages.
Fairbourne sits on low-lying land behind a shingle embankment with a 1m high concrete sea wall on top for further protection, and another embankment at the back of the village. It is surrounded by the mountains of Snowdonia and with a blue flag beach it is a beautiful spot. The Cambrian Coast main line railway has a station in the village and the settlement itself was founded as a holiday resort in the late 1890s by Arthur McDougall (of flour making renown).
Educating at risk communities
“I think it’s fair to say, knowing what we know now, that a long-term settlement wouldn’t have been built here,” says Royal HaskoningDHV coastal management consultant Greg Guthrie. “The place is well defended at the moment but in the Shoreline Management Plan for west Wales, Fairbourne was one of our main concerns for the future.”
It has taken a couple of years, not surprisingly, for the Fairbourne residents to really appreciate the issues and understand the technical problems. “People had different levels of understanding, but they are well educated, many being ex-professional people, and have got to grips with the issues, principally accepting the Inter Governmental Panel on Climate Change predictions of sea level rise. They understand now.”
Network Rail, too, will be facing difficult decisions in the long term regarding the increasing defence requirements for the Cambrian Line through Fairbourne.
Royal HaskoningDHV has reviewed the Barmouth Tide Gauge records and though the gauge only provides a relatively short-term data set, “it shows that local sea level rise is in line with the national average of approximately 4mm a year”, says Guthrie. “There is strong evidence that climate change is happening in line with the current projections, which could see 1m of sea level rise over the next 100 years.”
Moving the village
Moving the village over the next 40 years is one issue for public and local politicians to deal with, supported by the work Gwynedd Council is driving forwards. Another issue is the fear that one breach of the defences in a big storm will wash the village away in one go and though evacuation plans are in place, there will be nowhere for residents to return to.
“These are horrible issues for people to confront and we are seeing a decline in their wellbeing because of it,” Goodier says.
There is a Preliminary Coastal Adaptation Masterplan almost ready to be unveiled but there are still so many unknowns – where people will go and who will pay in particular. “There is money for defence but it will be far more difficult to get money for change,” Guthrie says.
“I don’t think anyone has ever done this before. It is similar to building a reservoir but when you move a community then, there is a definite date for the move and people get compensation. For this, there is no power to make people move and there is no compensation – all the risk resides with the property owners.”
Social change issue
While that approach is applicable to traditional flooding issues, Guthrie says: “In my mind this is different. This is social change and issues of compensation need to be looked at again.”
Around the coast of the UK other communities and individuals will be affected by the building impact of climate change. “We have to start dealing with the issues now,” he says. “If we wait until the impacts are really obvious in 20 or 30 years’ time we will have compromised the wellbeing of future generations and lost decades in being able to make changes without derailing people’s lives.”
In England the Environment Agency is aware that difficult conversations need to be had, and not just with people on the coast. Its deputy director of flood and coastal risk management, Clare Dinnis, is currently charged with putting together a strategy to 2050.
“We are looking at what society wants us to protect and how do we fund it,” says Dinnis. “That doesn’t mean building walls and stopping flooding but getting the balance right between resistance and resilience. So the right answer could be accepting that somewhere will flood but putting in place measures to make sure recovery can be achieved as quickly as possible.
“Water needs to be at the heart of decisions we make as a society – making space for water in new developments, for example. We also need to work with communities so they recognise that not only do they have to live with flooding but they have a part to play in reducing the consequences.
“The proportion of people who accept they are at risk from flooding is not as high as we think it ought to be. Acceptance is at the core and is the part we have started to talk about.”
Three hot topics
New Civil Engineer asked Mott MacDonald’s global practice leader for rivers and flooding Fiona Barbour for the key flooding issues to watch out for:
1. Working with natural processes
Also known as natural flood management, this is the practice of managing fluvial and coastal flood and erosion by protecting, restoring and emulating the natural regulation function of catchments, rivers, floodplains and the coast.
It covers anything from leaky dams to the re-meandering of rivers but beware, it is not a fix-all or a solution on its own. And there are occasions when slowing the flow upstream can make things worse by, for instance, inadvertently coinciding the peak flows of two rivers in a catchment.
2. Working with cities to better manage risk and enable building on flood plains
At the moment, decisions are made in a very black and white way about constructing on flood plains. But to stop it altogether will mean areas already in the flood plain will decline and new development will focus on green belt areas. Mott MacDonald is advocating the resilient building of non-residential properties that are designed to quickly recover from floods.
At the same time, all new construction should include attenuation storage that collects rainwater falling on the site and discharges it as if the site was green. Thus, development counteracts the past increased runoff from increased hardstanding. Where possible, the inclusion of both treatment and
storage in sustainable drainage systems (SuDS) could result in disconnection from stressed combined drainage.
3. Digital Twins
The benefits of digital twins have much to contribute to future flood planning and mitigation. Developing a digital
version of a city allows for rejuvenation to more easily consider the technical constraints and opportunities strategically.
Drawing data together in a common environment means we will be able to see how a city is used, how it works, where the water goes and therefore plan in a way to be smarter with existing assets that will better meet future flood management requirements.
Flood planning for England
This winter government will publish a policy statement on flood and coastal erosion risk management, setting out its future expectations for managing flood risk.
This will be followed in 2019 by the Environment Agency updating the national flood and coastal erosion risk management strategy ahead of the Comprehensive Spending Review of funding needs beyond 2021. The Agency, in a separate project, is also looking ahead to 2050 and beyond (see main feature).
Investment in flood and coastal risk management between 2015 and 2021 in England is £2.6bn and by the end of the period 300,000 homes will be better protected. The Environment Agency manages flood risk on 36,000km of river and 9000km of raised defences on the coast.
The Department for Environment, Food and Rural Affair’s 25 Year Environment Plan says that “without any further investment in flood defences the number of properties at medium or high risk could rise from 750mm to 1.29m in 50 years”. Current planning assumes a 1m sea level rise by the end of the century.
The second National Adaptation Programme (NAP) published in July said that flooding and coastal change represented a high risk to communities, business and infrastructure. Prevention, protection, adaptation, response and increasingly acceptance will underpin all future approaches to dealing with flood risk.
Almost at the same time as the NAP, the National Infrastructure Commission’s (NIC’s) first assessment has urged government to consider following the Dutch example and putting in place a national standard for resilience by 2050.
“Decisions about capital investment have generally been made on the basis of cost benefit analysis. Essentially this involves an assessment of whether it is ‘worth’ protecting particular homes and commercial properties. This is not a sustainable basis for decision making,” the Commission said.
The Commission’s judgement is that all properties, wherever feasible, should be resilient to severe flooding, with a 0.5% annual probability by 2050. A higher standard should be provided for larger cities of 0.1%.
“The NIC has put a really relevant question on the table in the context of climate change about what level of flood resilience schemes should be designed to,” says Environment Agency director of allocation and risk management – flood and coastal management Ken Allison. “We welcome having that debate opened up.”