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Don’t Ignore Surface Water Runoff, Report Warns

When it comes to the UK’s water-related aspects of the climate crisis, there’s always a lot of talk about water pollution and shortages in supply, but there’s one topic that risks being left out of the discussion and that’s surface water flooding.

This is something that a new report from the National Infrastructure Commission (NIC) seeks to address, an issue that is expected to become more urgent as time goes on and climate change drives more frequent extreme weather events, such as storms and flooding.

Periods of heavier and more intense rainfall will become more common as the climate changes and global temperatures continue to rise. Drainage systems can quickly become overloaded in a sudden downpour and this can lead to surface water flooding, putting many homes and businesses around England at risk.

As it stands right now, there are approximately 325,000 properties in areas at the highest risk of this kind of flooding, with more than a 60 per cent chance of being flooded in the next 30 years. If action isn’t taken – and soon – a further 295,000 properties could be facing similar risks.

Part of the problem is that surface water flooding is highly localised and very difficult to predict and, as such, local solutions are required in order to help protect those most at risk, with funding devolved and more support for communities to make long-term strategies and reduce these risks.

Mitigating urbanisation impacts

The report calls on the government to take steps to reduce the impacts of urbanisation and help ensure that the processes and procedures for new developments are doing enough to help reduce the amount of rainwater flowing into drainage systems.

Legislation was enacted in 2010 to improve new development delivery of surface water drainage but the legislation was never enacted. Changes were also proposed to Schedule 3 of the Flood and Water Management Act to make sustainable drainage a legal requirement but this was not implemented either.

And this year, a government review was carried out to decide whether or not to implement this Schedule 3 in England, but a decision is currently still pending.

The report urges the government to implement the Schedule and update technical standards for sustainable drainage. It also wants to see a comprehensive review of the effectiveness of the various options to manage increases in impermeable surfaces, as well as a decision as to whether policy changes are needed to reduce surface water flooding impacts.

Improving drainage systems

In addition to the above recommendations, the NIC report stresses the importance of maintaining and enhancing drainage systems to help protect those properties already at risk and to help prevent more sites being affected in the future.

Interventions should follow a solutions hierarchy, which prioritises maintenance and optimisation, followed by above-ground solutions and with below-ground pipes and sewers considered last.

Approaching the problem in this way will ensure that the lowest-cost options are looked at first, while making the most of opportunities to drive wider benefits like biodiversity improvements.

Setting national risk reduction targets

Another key recommendation for the government included in the report is the setting of national risk reduction targets to help monitor progress. While there are currently goals in place to reduce overall flood risks and provide property protection by 2027, there are no long-term targets established for surface water flooding risk reduction.

Analysis shows that an investment in cost-effective drainage infrastructure of around £12 billion over a 30-year period could reduce the number of at-risk properties in 2055 by approximately 60 per cent.

Quantifiable targets should also be identified to help drive and monitor progress at a local level, with upper tier local authorities, internal drainage boards and water/sewerage companies working to include these as part of their single joint plans.

Water companies have a key role to play

Water firms have a duty to provide, improve and extend public sewers, as well as maintaining them to make sure that drainage is effective in their catchment areas.

However, this is typically interpreted as meeting the entitlement to connect to sewers to discharge surface water and address sewer flooding. As such, the report recommends that the government clarifies its priorities for Ofwat to enable suppliers to make investments and manage surface water flooding risk.

Water companies should also be encouraged further to deliver both above and below-ground solutions, with Ofwat ensuring that the next Price Review period in 2024 sets a level playing field for these interventions, including sustainable drainage systems.

Devolving local funding

Greater certainty over funding will be required for local authorities if they’re to make long-term plans to reduce their communities’ flood risks. To support this, the report recommends that funding be devolved to those local authorities in new flood risk areas to help manage surface water flooding, as well as other risks.

It further suggested that these budgets initially be set for 2026-2031, with allocations based on assessment of risk level in each new area. Working in this way should ensure that the funding is spent more effectively, the report authors continued, since local organisations are more likely to have a better understanding of local risks and the potential solutions.

Commenting on the findings, national infrastructure commissioner professor Jim Hall said: “It’s clear that faced with more intense rainfall and increased urbanisation, we need to start taking this type of flooding far more seriously. The solution is clear – reducing the amount of water flowing into drains, whilst also improving the capacity of those drains.

“That means stopping urban creep from increasing the amount of stormwater that drainage systems have to cope with and giving nature more opportunities to hold on to excess water, as well as targeted investment to ensure sewers can cope with growing pressures.

“While sustained investment is needed, the estimated additional costs are relatively modest. At least as important is a more joined-up approach to owning and acting on the problem.”

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