‘LET’S ACT NOW TO TACKLE FLASH FLOODS IN CAPITAL’

Councils must work together to tackle the increased threat of flash floods, with a huge amount of investment needed to build a modern infrastructure, says London Councils

The risk of flash floods in the capital is likely to increase due to the impact of climate change, warns London Council’s Surface Water Flooding Task and Finish Group. This is backed up by the increased frequency with which parts of the capital has been ravaged by flash floods.

On the 12 and 25 July 2021, the capital was hit by intense rainstorms which overwhelmed the drainage systems, resulting in extensive surface water and sewer flooding, affecting homes, businesses, health infrastructure and transport networks. Flash floods affected 24 boroughs, with the worst impacts felt particularly in parts of east and north London.

On 17 August 2022, flooding occurred in Stoke Newington, Stamford Hill and Walthamstow and outside Victoria and St Pancras rail stations. Holland Park, Kentish Town, Earls Court, Turnpike Lane and Loughton tube stations also had to close due to flooding.

And on 3 November 2022 emergency services responded to flooding incidents across London following storms, with properties flooding and a number of calls from people trapped in their cars.

What causes flash floods?

Surface water flooding occurs when the drainage system is overwhelmed, and rain cannot get into local drains, sewers, or watercourses.

London’s built-up infrastructure makes surface water flooding difficult to manage, which is made worse by an increasing area of impermeable surfacing and a Victorian drainage system, which was “not designed to cope with the current and predicted future populations of London”, says the Task and Finish Group.

Also, the unpredictable nature of surface water flooding, makes it hard to provide an accurate warning or alerts system, says the report. While mapping and modelling offers a clue to where flooding may occur, “it is less clear that residents in risk areas understand the level of risk that they face and how to respond”.

It notes that there is no single organisation in overall charge of managing surface water flood risk in London. They also point to insufficient funding to manage the risk and a lack of modelling to show where floods are likely to occur.

Time for a strategic vision

A strategic vision and plan should be developed by a ‘transition group’, with a Surface Water Flooding Strategic Forum launched by next year, said the report.

“These recommendations are ambitious, but the Task and Finish Group members believe them to be in-line with the seriousness of the situation and the level of need,” said the report. “Surface water flooding presents a clear threat to life as well as significant economic costs due to damage to residential property and businesses.”

London Council's findings were echoed in an independent review for Thames Water which said the July 2021 floods are likely to happen more frequently in the future.

“Consequently, as flooding is not any one organisation’s responsibility, the review notes that the many parties which manage flood risk in the capital must work together to identify solutions to manage multiple sources of flooding and identify potential funding to ensure that the impacts of flooding are managed effectively.”

As proposed by London Councils, the review called for the setting up of a new body. This would take a “strategic view and governance with all parties contributing so that surface water and sewer systems can be assessed together, and investments designed to optimise outcome across different organisational boundaries”.

Hackney’s mayor Philip Glanville, chair of London Councils’ Transport and Environment Committee, welcomed the commitment shown by partners – the Mayor of London, the Chartered Institution of Water and Environmental Management, the Environment Agency, the London Resilience Partnership, the Thames Regional Flooding and Coastal Committee and Thames Water – “to work together to deal with this pressing and critical issue”.

“It is essential we work together to improve cohesion and collaboration around flooding, which will only get worse due to climate change. However, currently there is not one single organisation responsible for dealing with surface water flooding, which makes solving problems more complex.

“Looking towards the future, a huge amount of investment will be needed to build a modern infrastructure that protects Londoners from flooding. Although we are looking at an investment model for achieving net zero more generally, the capital is already facing a backlog of over £1bn in road maintenance work alone and boroughs need considerable funding in order to deal with this backlog and establish new sustainable drainage solutions.” n