Over coming decades, the effects of climate change are likely to lead to more extreme weather events.
This means more heavy rain storms. Storms so intense that rainwater often cannot drain away very easily and overwhelms existing drainage systems.
This leads to localised surface water flooding. This is a separate type of flooding – particularly affecting urban areas – that’s distinct from coastal or river flooding.
Surface water flooding is a significant, and growing, risk
Our study has found that over 300,000 properties in England are currently in high risk areas, compared with 240,000 at risk from river and coastal flooding.
The chances of these high risk areas experiencing surface water flooding is 1 in 30.
Without action, we think that by 2055, up to 295,000 further properties could be put at high risk.
Why does this matter?
The impacts of surface water flooding are considerable. It can cause significant damage to properties and shops, disrupting businesses and communities.
But it can also lead to major problems for our transport and energy networks.
Right now, the way this risk is dealt with is fragmented. The Environment Agency, local government, our water companies and Ofwat all have a role in how the country manages the risk.
But there are no clear targets for alleviating the risk, or clearly defined responsibilities for who should take action, and when.
surface water flooding?
Rainfall on a pavement
Rainfall on a pavement
When it rains heavily during a storm, water will soak into the ground or run off into local water courses, such as streams and rivers.
In areas with plenty of roads, tarmacked driveways and large paved areas, it can be harder for water to drain away, leaving it to run down the street and into gutters.
While it isn't feasible - or affordable - to completely eliminate the risks from surface water flooding, we can do more to reduce them.
Better management of
surface water flooding
We think there needs to be a long term target for reducing the flooding risk, which can be turned into local targets and plans to target action ...
... backed up by £12 billion in public and private funding over the next thirty years, to tackle the risk effectively.
There are three main ways to improve the situation.
1. Stop as much of the water as possible getting into drains
The growth of hard, impermeable surfaces - such as when people turn their gardens into driveways - reduces the chances for water to drain into the ground.
So too does the growth of major new developments.
We think government should set out by the end of 2024 the policy changes it thinks are necessary to mitigate the impacts of surface water flooding and limit the impacts of growing development.
2. Expand the capacity of drainage systems
Existing drains need first of all to be better maintained.
Wider adoption of more sustainable drainage systems that use natural processes, such as ponds and streams, to allow storm water to drain away safely over time will help.
But there will also inevitably be a need for more below ground solutions - additional pipes and sewers - as the last resort for increasing capacity.
3. Create more joined-up, targeted governance and funding
A new approach, supported by the Environment Agency and Ofwat, would see local authorities and water companies working together on fully costed joint plans for each surface water flood risk area.
We recommend that public funding is devolved to local areas to assist with longer term planning.
Better targeted, devolved funding will help protect thousands more properties
Targeted, cost effective investment
Improved maps and models would help inform overall national estimates of the funding required to tackle the problem.
Total investment costs would continue to be split between public funding and private funding - that is, investment provided by water companies which is ultimately paid for by bill payers.
We estimate that the level of new infrastructure needed will cost £12 billion spread over 30 years, split between both public and private funding.
Our analysis suggests this level of funding makes sense in any realistic future climate scenario, offering a 'low regrets' solution.
The Commission’s modelling suggests these steps could move 250,000 properties out of the high risk category, and boost protection levels for thousands more properties.