Flood Prevention: Rainwater Attenuation and Reservoirs

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.

I also want to mention rainwater harvesting. Many developments are now including rainwater harvesting—what we call grey water—and I believe we will see a great deal more of that going forward. Again, it is very much an MHCLG agenda in the planning guidance.

The question of building on floodplains was also raised. The Environment Agency comments on all applications for development on floodplains. It gives advice, but it is the local planning authorities that make the decisions about whether the housing should go forward, so it is very much a local decision and up to the local authority to have its own plans about what it thinks is correct or not. The hon. Member for Warwick and Leamington raised some good points on that agenda.

It is not just the risk of drought that might be considered. If we are to use reservoirs for flood management purposes, it is essential that the water levels are managed so as not to add to the flood risk. Drawing down a reservoir ahead of wet weather may make a contribution to the protection of properties downstream, but it is crucial that when that water is released it is done so in a timely and controlled way. We all recognise that timing is everything. To release water when the river levels are already high and the ground is saturated, as it is right now, could have the opposite effect and increase flood risk further down the catchment.

It is true that water companies are not restricted by either current legislation or Ofwat from managing their water resources to provide a range of benefits, including flood risk management. However, as I have already explained, any decision must carefully take into account how a water company can continue to meet its water supply duties as set out in the Water Industry Act 1991. As the regulator, the Environment Agency will have to consider the ability of water companies to continue to meet that duty when making decisions. It is very important to take such considerations into account. They include the funding implications, such as the possible impacts to water companies’ bills in replacing water sources or reducing the security of customers’ water supplies.

The Environment Agency will continue to support and work with the water companies and local partners to further explore this issue, recognising that any opportunities are likely to be very site-specific. I very much look forward to hearing what options might be possible, because we clearly have to think of a wider range of options for all these measures, whether it is about water supply, flood mitigation or trying to achieve both.

Be in no doubt that the Government fully recognise the concern and anxiety of communities affected by flooding, as well as those who might be affected later by drought. We understand why, on the face of it, reservoirs may appear to be an obvious solution for some communities. However, the challenges of using water supply reservoirs to manage flood risk are specific and unique and we should not assume that there are simple solutions to this complex area.

We have changing weather patterns and more frequent incidents, whether they are flooding or drought, together with our growing population and its ever-increasing demand for water—and I absolutely take on board the hon. Member’s comments about the use of water. A consultation has been done recently on water consumption and how much we are all using, with a view to each of us individually cutting down our water usage.