Flood Prevention: Rainwater Attenuation and Reservoirs

Jim Shannon Excerpts

Monday 9th March 2020 Commons Chamber

[Matt Western (Warwick and Leamington) (Lab)]

I rise to speak this evening on the topic of improving rainwater attenuation and storage, and preventing and mitigating flooding. For millennia, we have lived in this country in a temperate climate—a green and pleasant land, according to the immortal words of William Blake. We have enjoyed rain, but what we have seen in recent years and decades is freak weather, increasing rainfall and intense rainfall events. This February was the wettest month on record.

In my constituency, Welches Meadow—a field adjacent to the River Leam—has been under water for many weeks now. When I travel here by train, I pass through Warwickshire and Oxfordshire, and I see so many fields still inundated with water. Across the country, we have seen extraordinary weather events over many months, most recently with Storm Ciara and Storm Dennis, which have brought about so much devastation and damage. There have been winds of up to 80 or 90 mph, and my feelings and thoughts go out to all the communities that have been so affected: the Calder valley, Cumbria, Yorkshire, Derbyshire, the south-west, the south-east, Northern Ireland, Scotland, Wales—right across the country. We saw the extreme impact of Storm Dennis on south Wales just a few days ago. Back in November, there was flooding across Yorkshire, Lincolnshire and Derbyshire. We were told that this was a one-in-60-years event, according to the experts. But as we saw in Doncaster with 3 inches of rain falling in 24 hours, these events are happening so much more frequently than they were a few decades ago. I think back to 2004 and the terrible flooding in Boscastle—that tragedy when the rivers overflowed and the little town was almost washed away.

[Jim Shannon (Strangford) (DUP)]

I congratulate the hon. Gentleman on raising this important issue. Does he agree that the recent floods have highlighted the fact that there must be a designated strategy—we look to the Minister for that—to deal with overflow? Does he agree that the harvesting of rainwater via attenuation ponds on farmland should be further investigated and initiatives introduced to make this attractive to farmers and landowners as a way forward in solving some of the flooding issues?

[Matt Western]

The hon. Gentleman makes a terrific point, as always, and I welcome his contribution, as ever. I will come on to those points a little bit later.

In Warwick and Leamington, we have had, over the years, serious flooding events ourselves. Back in 1998 and 2007, we suffered too, so I have compassion—as do, I am sure, my communities—for those who have been affected in recent weeks and months. In the watershed that we sit in of the Leam—the Avon river that feeds into the Severn—we are quite a way upstream and so relatively less affected than places such as Tewkesbury and elsewhere further down in the Severn valley.

Key to all this is managing flooding and the attenuation of the rainwaters, slowing the flow so that rivers, drains and other natural drainage can manage. Most of the time, natural systems can cope well, but when we see these extreme peaks, we need better management. So the priority must be for natural solutions, but they are not enough. Evidently, as we have seen, there needs to be urgent intervention and investment, but also, I would argue, a change to the planning and building regulations and how we use reservoirs.

Let me first deal with planning. Planning is of course critical—what is built where, bearing in mind the topography and the relationship with the watershed. I think back to the national planning policy framework, where too much power was given to developers to use land as the location for housing built at the wrong densities for communities in, all too often, the wrong places. I look to the south of Warwick and Leamington, where I am sure that the new residents who have moved in would have preferred to live in much higher densities with greater services, greater transport infrastructure and so on. Building over so much farmland has reduced the availability of land to absorb these high-rainfall events. Homeowners across the country have had their homes built on floodplains in areas where they can no longer get insurance, or if they can get insurance, the cost is prohibitively high and they are suffering because they cannot afford it. They are almost excluded from having insurance because of its cost.

Let me turn to building regulations. I think back to the Climate Change Act 2008, when we were promised zero-carbon homes by 2016. That was followed by the tragic Budget from the incoming coalition Government that tore up all that vision—that ideal—to see those great new Passivhaus homes built that recognised the importance of the environment in the equation. I am afraid that the Cameron Government of that time presided over the greatest act of environmental vandalism. Millions of homes have been built since, and their owners have missed out on what could have been fabulous zero-carbon or very-low-carbon homes. There was also the failure to recognise the importance of water in our environment. In his April 2011 speech, David Cameron said: “I want to rip up red tape. I want to get rid of that green cack”—I think that was the word. He got rid of the code for sustainable homes and replaced it with building regulations that did not go far enough. He wanted to save his friends the builders more money. He stated that, by changing the regulations, the builders would save £500 a home, giving them £60 million more a year in revenues. We have only to look at companies such as Persimmon, which is the most high-profile example, and the sort of profit it has made since to realise that that was a short-term and disastrous policy.

The building regulations could have included more sustainable water attenuation. Things such as sustainable urban drainage systems have been introduced, but I believe that greywater harvesting could have been the critical difference. Systems for the use of rainwater collected at source and stored are as cheap as chips, and for new build homes, they could have made a massive difference. Built at scale across new communities, they would have provided a huge rainwater storage capacity upstream, controlling the release of water into drains. When I renovated my home 10 years ago, I managed to put in a 1,500-litre capacity. For the 20,000 homes being built around Warwick and Leamington, that would have equated to 25,000 tonnes of rainwater being captured.

When researching this subject, I looked at fabulous periodicals such as Water. An article in July 2019 says:

“Different studies showed that, in urban catchments, the extensive installation of rainwater harvesting tanks could be an efficient support for reducing frequency and peak of stormwater flood.”

It cites some research that was done in the UK, while researchers in China found that

“the system has a good performance in mitigating urban waterlogging problems,”

reducing flood volume of 14%, 30% and 58% in the cases of maximum daily rainfall, annual average maximum daily rainfall and critical rainfall respectively.

Those are impressive figures, but as technology moves on, we see the introduction of smart rainwater harvesting systems. Another paper by academics was produced in Water in November last year. The study concluded that:

“smart rain watertanks operated as a system in real-time during a storm event… can significantly reduce the downstream peak runoff flow rate for a wide range of storm durations”—

30 minutes to 24 hours—and frequencies of between 50% and 1% annual exceedance probability. It went on to say:

“this is the first study to demonstrate that household-scale rainwater tanks could potentially provide peak flow attenuation performance across a wide range of storm event durations for rare events”—

in other words, a 10% to 1% annual exceedance probability. I cite that research to show that these systems are out there; we just have to adopt them as policy. That is what needs to be done, because after energy, water is a massive issue for us.

Per person, we use 142 litres of water per day, and a household uses 350 litres. If we were to introduce rainwater harvesting tanks, we would be able to assist in the demand and consumption within a property, not just the storage, which would help to mitigate flooding. We use 840 billion litres of water a year just for showers, 740 billion litres for flushing our toilets and a further 360 billion for washing machines and dishwashers. Some 25% of total water consumption is used for showers, and 22% just goes straight down the toilet. I see this as a huge opportunity to reduce bills and aid flood management. If we combine the greywater supply for toilets, washing machines and use in the garden, it would account for a third of the total and could save each household up to £150.

The third change I propose is in regard to reservoirs and detention ponds. I urge the Government to provide the Environment Agency with greater powers, to enable it to work more closely with the water utility companies, as proposed by my hon. Friend the Member for Halifax (Holly Lynch) in her Reservoirs (Flood Risk) Bill. Such an approach would allow the water companies to run at lower levels in reservoirs when high rainfall is anticipated, and the trials undertaken by Yorkshire Water at six reservoirs upstream in the Calder valley have shown that this could greatly mitigate flood events if run at levels below 100%. It has trialled it at 90%, and now it is going to trial it at 85%. As I understand it, similar trials and conversations have been happening at Thirlmere reservoir in Cumbria, and at the reservoirs in the upper Don valley and at Watergrove reservoir in Rochdale.

A change in the legislation is needed. As the hon. Member for Strangford (Jim Shannon) so beautifully put it, we have huge opportunities, particularly with farmland. I speak to farmers in my local area, and I spoke to those at Canalside—a community supported agriculture project just outside my constituency, with which I used to have a considerable involvement—and they cannot sow or put in onions for the next harvest because the ground is so waterlogged. That is what we are seeing for farmers all over the UK.

To summarise: what we have witnessed—not in recent weeks or months, but actually years—is that we are having more frequent, more intense and more severe weather events than we were having 30 years ago. I lived in London 25 years ago and I now of course live here again, and when I compare and contrast the sort of weather we are having now, I see that the climate has really changed in that 25-year period. It is really quite remarkable.

My thoughts are with all the communities that have been affected by these terrible floods most recently, but we have the wit and the knowledge to bring about change. If we change the planning legislation, do not build on the floodplain, change the building regulations and reintroduce the code for sustainable homes, plus include the fitting of greywater or rainwater harvesting systems, it would be as cheap as chips, as I say, for any new build property. That is what we can do: we can build storage upstream in these communities for them to use the water, or for it to be released when it is the right time to do so, and ease the pressure on the precious infrastructure that we have in our drainage system. At the same time, we could turbo-boost the sustainable urban drainage schemes, and introduce more small reservoirs, detention ponds, swales and infiltration basins.

I also urge the Government to revisit the scheme for an Abingdon reservoir, and likewise in Maidenhead and elsewhere across the country. To my mind, if we are prepared to spend £1 billion a year on flood defence measures, surely a more sensible thought is to spend money further upstream, think about how we can detain the water, think about attenuation systems—I evidenced that through the two academic papers detailing what can be achieved—and, finally, give the Environment Agency greater powers over reservoir management, as proposed by my hon. Friend the Member for Halifax, which I believe would be a very welcome amendment to the Environment Bill.

--- Later in debate ---

[Rebecca Pow]

But it still stands that it is a local planning decision to allow building on floodplains to go ahead, and that is very much an MHCLG agenda.

I want to talk about the reservoir issue that the hon. Gentleman raised. Many people are suggesting that that provides a simple answer to some of our flooding issues and also our water supply issue, but of course they are very complex issues involving a range of stakeholders and they have to be considered in relation to how reservoirs might be managed and operated throughout the year. On that, I must give assurances that flood and coastal erosion risk management is a big Government priority now, with £2.6 billion already devoted to this area in the last spending round up to 2021 and the recent announcement, to be confirmed in this week’s Budget, of funding for flood defences of £5.2 billion. That will be helping a further 2,000 new flood and coastal defence schemes and better protect 336,000 properties across the country.

There are of course reservoirs at the moment that are used for flood risk management. The Environment Agency operates more than 200 reservoirs around the country, especially for flood attenuation. That is their purpose in life and the amount of water in them during non-flood conditions is kept deliberately low in order to maximise the storage available during high rainfall and storm events. Many of those reservoirs have been operated this winter, and, in combination with other flood defence measures in the catchment, have provided protection to a great many people.

[Jim Shannon]

Farmers and landowners are not averse to the idea of setting some of their land aside for attenuation ponds. Might the Minister and her Department incentivise that with some sort of grant for land set aside for that purpose? It is not just the farmer who gains, but the other people in the area, particularly householders.

[Rebecca Pow]

The hon. Gentleman will know that in the Agriculture Bill that has just gone through its Committee stage, farmers will be paid for delivering public goods. Flood resilience is included, so consideration will be given to a whole range of projects, which could include farmers holding water on their land to help with flood alleviation.

I return to the issue of reservoirs; water company reservoirs in particular were mentioned. Our water company reservoirs have a very different purpose in respect of drought attenuation—we must not forget that only months ago we were facing potential drought scenarios. Over summer 2018, the country dealt with very dry and warm weather, with water companies experiencing some of the highest demand for water for their customers. We have to pay as much attention to the risks associated with too little water as we do to those associated with too much.