ADD2758 Surface-water flooding – basements campaign 2025

1.1.    In July 2022, under approval of Assistant Director Decision (ADD) 2584, a flash-flooding leaflet was distributed to 46,832 basement properties in London, with key messages about the risk and what to do if a flash flood event is forecast. 
1.2.    In July 2023 a leaflet on the same topic, with more detailed information, was distributed to 48,000 basement properties. Leaflets were also circulated to community groups and hubs at a more grassroots level. This leaflet contained an insert detailing the collective action of the boroughs, the Mayor, the Environment Agency and other partners to tackle surface-water flooding. 
1.3.    In 2024, a leaflet was circulated to 55,661 properties. This was the same as the 2023 leaflet, but contained an updated insert highlighting the latest updates on the Mayor’s activities to tackle surface-water flooding, and wider water-related initiatives. 
1.4.    This year we would like to repeat this exercise during London Climate Action week (21-29 June 2025). We will continue the 2023 and 2024 activity of including an insert; and will again circulate the leaflet (and insert) to community groups. 
1.5.    This year’s leaflets will be distributed with the following particular support for the campaign:
•    The London Surface Water Strategy (LSWS) report, due to be launched in May 2025, emphasises the high flooding risk to basement properties. It also refers to the distribution of leaflets as a part of stakeholder engagement and public awareness campaigns. The LSWS report incorporates the ambition to ‘empower people’, which includes improving public awareness of surface-water flood risk and empowering people to take individual action to protect themselves. 
•    London’s Clean and Healthy Waterways programme, which emphasises how sustainable drainage systems are a key benefit – not only in reducing flood risk, but also in reducing pollution in London’s waterways. 
1.6.    The leaflet will remain the same as the 2024 leaflet, but the insert will be updated. The GLA’s climate adaptation team has led on this update; but partners, including members of the surface-water flooding strategic group, have also been closely involved.
1.7.    The leaflet and insert have been drafted with input from the Environment Agency, Thames Water, London Fire Brigade, London Resilience, the GLA Urban Resilience team, London Councils and the London Drainage Engineers Group (lead local flood authorities from boroughs are also represented in this group). The leaflet has been designed by the GLA’s design team using the Mayor of London branding.
1.8.    The GLA’s print supplier CDS Ltd has provided a quote of £48,903 to print, envelope and distribute 56,000 leaflets to basement residents across London. The final number of addresses has not been confirmed, but will be around 56,000. We will direct-mail the leaflet to these addresses; further leaflets will be distributed through other channels.
1.9.    These other channels will target Londoners most at risk with priority targets, such as older people and disabled people. Among these channels we include community groups, faith groups and neighbourhood networks who can identify these Londoners, and share as appropriate with the communities in their neighbourhoods. We are working with other GLA teams to identify the most effective channels to target alongside a physical mailout/leaflet drop. These teams include the Environment Communications team; External Relations; the Resilience Unit; the Communities team and the Migration team (working together to consider the private rented sector and the specific needs of migrants in basement dwellings); and the London Resilience Group. We are also working with external partners: last year we worked with the National Flood Forum, Age UK and British Red Cross, who have various channels where they can share the leaflet with Londoners. We aim to do the same again this year. 
1.10.    The basement properties have been identified through various data sources. In 2022, the Ordnance Survey AddressBase Plus dataset identified just under 30,000 properties. Working with Geoplace, the central source of information for all UK addresses and streets, we identified nearly 14,000 more addresses using energy performance certificates. Another 1,200 were identified from the GLA planning team’s Datahub; and 1,900 were identified from the GLA’s building stock model. In 2023, we identified up to 1,000 further addresses from an AddressBase Plus update in March of that year. We also worked with partners to find additional addresses. 
1.11.    In 2024 we found significantly more addresses from updated datasets, taking the total to just over 55,000 addresses. In 2025, we will repeat last year’s exercise to see if any more basement properties have been identified. A secondary benefit of identifying these addresses is that this data can be shared with boroughs, to use in their flood risk plans. Many boroughs have requested the data, and used it to plan targeted work in areas with many basement properties. 
1.12.    We also received many orders for leaflets from community groups, some of which we could not fulfil as the high level of demand was not anticipated. This year we plan to make more leaflets available for community distribution, to fulfil requests from these groups.  
 

2.1.    The objectives of the campaign are to:
•    raise awareness about the risk and what to do if a flash-flood event is forecast 
•    reach as many basement properties as possible through this leafleting campaign 
•    encourage individuals and communities to take low/no-cost actions before a flash-flood event, and explain what to do during a flood.
2.2.    The expected outcomes of the campaign are: 
•    basement residents are more aware of their potential risk from flash flooding, and what to do if one is forecast in their area 
•    Londoners generally are more aware of their risk from flash flooding through the wider communications work.
 

3.1.    Under section 149 of the Equality Act 2010, as a public authority, the Mayor of London must have ‘due regard’ of the need to eliminate unlawful discrimination, harassment and victimisation; and to advance equality of opportunity, and foster good relations, between people who have a protected characteristic  and those who do not. This involves: having due regard to the need to remove or minimise any disadvantage suffered by those who share a relevant protected characteristic; taking steps to meet the different needs of such people; and encouraging them to participate in public life or in any other activity where their participation is disproportionately low. 
3.2.    Climate change will disproportionately affect those least able to respond to and recover from it. Poorer Londoners will find it more difficult to recover from flooding. Extreme events will have a greater impact on older people; very young children; socially isolated people; and people with existing health conditions and disabilities. This campaign aims to inform people of their potential risk and what they can do to help themselves.
3.3.    This campaign is specifically trying to target those more vulnerable to the effects of flash flooding, and those living in basements. As part of the wider communications around the leaflet, the campaign will target older and disabled Londoners, to make sure they receive the information to help reduce their risk. As community groups and other organisations will have to request leaflets, we can monitor how many are distributed.
 

4.1.    The key risks and issues for leaflet campaign are outlined in the table below: 

4.2.    The basement leaflet campaign will contribute towards the Mayoral mandate to Delivering a Greener, More Climate-Resilient London. It also supports the London Environment Strategy’s aim to make Londoners resilient to severe weather and longer-term impacts of climate change, including flood, heat and drought.  
4.3.    None of the GLA officers involved in the drafting or clearance of this form are aware of any conflicts of interest with the proposed programme. 
4.4.    The address data that will be used contains no personal information; no names are used as part of the address. The letter will be addressed to “basement resident”.
 

5.1.    Approval is requested for expenditure of up to £50,000 towards the flash-flooding basement leafleting campaign. 
5.2.    Expenditure will be funded from the Adaption budget within the Environment unit’s approved 2025-26 budget.
5.3.    All expenditure will be incurred within the 2025-26 financial year.
5.4.    The programme is linked to the Delivering a Greener, More Climate-Resilient London delivery plan and there is budget within the delivery plan for this programme.
 

6.1.    The project will be delivered according to the following timetable: