This briefing updates members on the recent launch of the Basement Flash Flooding Campaign and provides an update on the recent actions undertaken by London Councils and partners following the floods of 12th and 25th July 2021.
Background
On 12 and 25 July 2021, London experienced intense rainstorms that overwhelmed the drainage systems and led to extensive surface water and sewer flooding, affecting homes, businesses, health infrastructure and transport networks. Twenty four boroughs were impacted, with the worst impacts felt particularly in parts of east and north London. Amongst the actions undertaken following the event, boroughs, together with the Environment Agency and other relevant partners established a Task and Finish Group to explore the issue of long-term surface water flood risk management. Further details can be found in the member briefing “Surface Water Flood Risk Management in London”. One of the key areas of concern highlighted was basement properties as flood risk is considered to be high but there is a lack of data concerning precise level of risk and location of properties as well as occupiers having a lack of understanding of the risk, the need to prepare and what to do in case of emergency.
As a first step, an informational campaign has been planned to send out to properties in boroughs who may most at risk during the flooding season this year. The campaign is keen to build on Londoners’ awareness of the risk and the actions they can take, drawing on the experiences of the flash floods in summer 2021.
The campaign created key messages with input from multiple agencies and the boroughs and created an information leaflet (attached below). The leaflet will be sent out to around 45,000 properties via Royal Mail and is expected to land in homes from the 4th/5th July 2022.
The campaign has focused on basement properties as those that are high risk from flash flooding events, although other addresses for properties that have basements (over more than one floor), such as maisonettes, have been included in the dataset.
The dataset was formed using various methods. The bulk of the addresses came from a product called Addressbase Plus from Ordnance Survey. GLA also worked with Geoplace who supplied basement flagged addresses from Energy Performance Certificates (EPCs). A small portion of the addresses came from the GLA’s datahub which provides planning data from the boroughs. They also used the GLA’s London Building Stock Model (LBSM) to find additional basements. The GLA will be continuing to work on this dataset over the coming months to improve it.
There is basement data for every London Borough. The greatest number of basements are in inner London boroughs. The top five by numbers are Kensington and Chelsea, Islington, Westminster, Hammersmith and Fulham and Hackney.
You can access more information on flash flooding through the GLA’s website. The page builds on the detail in the leaflet and includes wider information e.g. on recovery after a flood, making your property more flood resilience etc. Agencies involved: London Councils, London boroughs, GLA, LFB, the Environment Agency, Thames Water
Commentary
This campaign represents an initial step towards improving public awareness of the risks of surface water flooding. The work of the Task and Finish Group clearly underlined profound weaknesses regarding London’s approach to surface water flooding. Subsequent engagement by officers within both the UK and internationally has shown that successful management of surface water flooding is frequently a long-term multi-decadal project, requiring strong on-going political and public support as well as the identification and implementation of significant resource. As London moves towards a warmer future flooding events such as those seen in July 2021 will become more frequent and severe. London Councils climate change polling has demonstrated that Londoners are both extremely concerned about climate change and are willing to actor both mitigate and adapt. Utilising this public support will be key to successful long term management of surface water flooding.
You can download the Flood Aware leaflet here [PDF]