SECTION 19 FLOOD INVESTIGATION: SEPTEMBER 2024 FLOOD EVENT

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Decision / Minutes Document

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Democratic Services 
 
Location: Phase II 
Ext: 0185 
DDI: 01895 250185 
CMD No: 1543 
To: COUNCILLOR EDDIE LAVERY 
CABINET MEMBER FOR COMMUNITY AND 
ENVIRONMENT 
 
 
c.c. All Members  of th e Residents’ Services Select 
Committee  
c.c. Ian Thynne,  Head of Environmental Planning 
Specialists 
c.c. Dan Kennedy, Corporate Director – Residents’ 
Services 
 
 Date: 10 October 2025 
 
Non-Key Decision request                        Form D              
 
SECTION 19 FLOOD INVESTIGATION: SEPTEMBER 2024 FLOOD 
EVENT 
  
Dear Cabinet Members, 
  
Attached is a report requesting that a decision be made by you as an individual Cabinet 
Member. Democratic Services confirm that this is not a key decision, as such, the Local 
Authorities (Executive Arrangements) (Meetings and Access to Information) (England) 
Regulations 2012 notice period does not apply. 
 
You should take a decision on or after  Monday 20  October 2025 in order to meet 
Constitutional requirements about publication of decisions that are to be made. You may 
wish to discuss the report with the Corporate Director before it is made. Please indicate your 
decision on the duplicate memo supplied and return it to  me when you have made your 
decision. I will then arrange for the formal notice of decision to be published. 
   
 
Liz Penny 
Democratic Services Officer 
 
 
Title of Report: Section 19 Flood Investigation: September 2024 Flood Event 
 
Decision made:  
 
Reasons for your decision: (e.g. as stated in report) 
 
Alternatives considered and rejected: (e.g. as stated in report) 
 
Signed ……………………………………………………… Date…………………….. 
 
Cabinet Member for Community and Environment 
 


 
Cabinet Member Report – 10 October 2025  Page 1 
(Part 1 Public) 
SECTION 19 FLOOD INVESTIGATION: SEPTEMBER 2024 FLOOD EVENT 
 
Cabinet Member & 
Portfolio  
 Cllr Eddie Lavery 
Cabinet Member for Community and Environment 
   
Responsible Officer  Dan Kennedy, Corporate Director – Residents' Services 
   
Report Author & 
Directorate 
 Ian Thynne, Head of Environmental Planning Specialists 
   
Papers with report  Section 19 Flood Investigation Report: September 2024 
 
 
HEADLINES 
 
Summary 
 
 The Section 19 Flood Investigation is a statutory requirement where 
a flood event of a significant nature occurs.   
 
On 23 September 2024, the Borough received approximately one 
month’s worth of rain in a day.  This led to widespread flooding, 
predominantly in Ruislip but also across other areas in the north of 
the Borough.   
 
The Section 19 Flood Investigation considers the causes of the 
flooding and makes recommendations about future actions that 
could help reduce the risk of flooding in the future.   
 
Officers are seeking Cabinet Member approval for the publication of 
the report and to pursue the recommendations.   
   
Putting our 
Residents First 
 
Delivering on the 
Council Strategy 
2022-2026 
 
 This report supports our ambition for residents / the Council of: 
Be / feel safe from harm 
 
This report supports our commitments to residents of: 
A Green and Sustainable Borough 
 
The Local Flood Risk Management Strategy 
   
Financial Cost  There is no immediate additional financial cost associated with the 
investigation.  The report was put together by the Flood and Water 
Management Team within existing budgetary resources.  
Recommendations for the Flood and Water Management team are 
expected to be undertaken as per statutory service arrangements.  
Recommendations for third parties would be subject to existing 
processes should those parties choose to carry them forward.   
   
Select Committee  Residents’ Services Select Committee 
   
Ward(s)  NA 

 
 
 
 
 
 
 
Cabinet Member Report – 10 October 2025  Page 2 
(Part 1 Public) 
 
RECOMMENDATIONS 
 
That the Cabinet Member for Community & Environment:    
 
1) Accepts the findings of the report and approve it for publication. 
2) Authorises officers from the Flood and Water Management team on behalf of the 
Lead Local Flood Authority to pursue the recommendations contained within the 
report.   
3) Authorises officers to notify the other Risk Management Authorities of the 
completed investigation in line with statutory requirements.   
 
Reasons for recommendation(s) 
 
Recommendation 1: 
 
The Section 19 Flood Investigation is a statutory requirement following significant flooding.  
Recommendation 1 seeks approval from the Cabinet Member to accept the findings of the report 
which follow from an extensive investigation carried out by Metis Consulting in partnership with 
Council officers.   
 
Recommendation 2: 
 
The Flood Investigation includes a number of recommendations of residents, communities and 
organisations.  Officers are seeking approval to adapt these into the existing strategy 
requirements in order to pursue flood risk reductions for people and property.   
 
Recommendation 3: 
 
It is necessary to notify other Risk Management Authorities (Thames Water, Environment Agency 
and Highways Authorities) of the investigation when it has been completed.   
 
 
Alternative options considered / risk management 
 
In this section: 
 
1) The Section 19 Flood Investigation is a statutory requirement and therefore ‘a do nothing’ 
scenario is not available.   
2) The Investigation sets out recommendations about future activity that relies on third 
parties.  There is a risk the report raises expectations that these activities will be carried 
out.  Officers will reduce this risk by improving the engagement and collaboration with these 
partners (e.g. Thames Water) in order to achieve shared objectives of reducing flood risk.   
 
Select Committee comments 
 
None at this stage. 
 

 
 
 
 
 
 
 
Cabinet Member Report – 10 October 2025  Page 3 
(Part 1 Public) 
SUPPORTING INFORMATION 
 
The Lead Local Flood Authority 
 
1. A Lead Local Flood Authority (LLFA) is the organisation designated under the Flood and 
Water Management Act 2010 to manage local flood risks in a specific area—typically a 
unitary authority or county council. In London, for example, each borough council (like 
Hillingdon) acts as the LLFA for its area. 
 
2. LLFAs have a major role in the coordination of flood risk management especially in relation 
to surface water flooding.  The LLFA has no operational remit in managing surface water 
and this is predominantly the function of Thames Water and the Highways Authorities (i.e. 
Hillingdon Council Highways Department).   
 
Section 19 Flood Investigation Requirements 
 
3. Under Section 19 of the Flood and Water Management Act (FWMA), the London Borough 
of Hillingdon, as the Lead Local Flood Authority (LLFA), has a statutory duty to investigate 
flood incidents deemed ‘significant’. A flood is considered significant when spec ific 
thresholds are met —for example, internal flooding to five or more properties, or when 
essential infrastructure such as major roads, hospitals, or utilities is disrupted or damaged.  
The purpose of a Section 19 Flood Investigation Report in Hillingdon is to: 
 
a. Examine the sequence of events that led to the flooding 
b. Record the number and types of properties affected 
c. Identify the Risk Management Authorities (RMAs) with responsibilities related to the 
flood 
d. Determine whether those RMAs have exercised, or intend to exercise, their flood 
risk management functions in response 
 
4. In compiling the report, Hillingdon Council has  actively engaged with residents, 
businesses, and stakeholders impacted by the event. Eyewitness accounts, local 
knowledge, and community -led suggestions have been considered to ensure the report 
reflects both the technical and lived experience of the flood. 
 
5. Once authorised, the Council will publish the findings and formally notify the relevant 
RMAs. As the investigation is carried out in collaboration with these authorities, the final 
report should provide an accurate and transparent account of the incident and the actions 
taken or proposed. 
 
23 September 2024: The Flood Event 
 
6. On 23 September 2024, parts of the north of the B orough experienced heavy rainfall 
amounting to a month of rain in one day.  The rainfall hit localised catchments as can be 
seen on the image below (the blue line shows rain falling at RAF Northolt and the green 
line at Pinner Cemetery).   
 

 
 
 
 
 
 
 
Cabinet Member Report – 10 October 2025  Page 4 
(Part 1 Public) 
 
 
7. The data, presented in Figure 3- 1, shows that the rain began just before 21:45 on the 22 
September, peaked around 00:30 on the 23 September, then stopped by 09:00. At the 
peak, 10.8mm of rain was measured within a 15-minute interval at the RAF Northolt gauge. 
Over a period of 11 hours and 15 minutes, a total of approximately 47.8mm of rain was 
received in RAF Northolt and 27.0mm was received in Pinner Cemetery. 
 
8. Reports of flooding began to be received throughout the early morning of 24 September 
2024, largely across locations in Ruislip.  There is no single flood reporting system in the 
Country, so reports were received by various first responders, including the London Fire 
Brigade, Environment Agency, Thames Water and the Council.   
 
9. A number of reports of internal property flooding were received which triggered the need 
for a post event Section 19 Flood Investigation.   
 
The Investigation 
 
10. As part of the investigation, the Council, in its role as the LLFA, undertook a ‘call for 
evidence’ towards the end of 2024 and into 2025.  The aim of the call for evidence was to 
secure information on what flooded and where, and importantly to get an understanding of 
the real-world flood experiences. 
 
11. There were 172 flood incidents reported in total as a result of the rainfall event. This 
included 123 reports of internal flooding and 49 reports of external flooding. Most of  the 
flood incidents were located in Ickenham and Ruislip.   
 
Findings 
 
12. The principal cause of flooding is that the drainage network failed to accommodate all the 
surface water from the heavy rainfall event.  The drainage network largely drains west to 


 
 
 
 
 
 
 
Cabinet Member Report – 10 October 2025  Page 5 
(Part 1 Public) 
the River Pinn (in Ruislip and Ickenham) and to the Yeading Brook (Eastern and Western 
branch) around Ruislip. 
 
13. These main rivers take surface water runoff from much further north in the catchment in 
Harrow.  The cumulation of surface water runoff  in such a short time frame meant the 
drainage network could not discharge and became ‘locked’ resulting in water backing up 
through gullies and manhole covers causing flooding.   
 
14. In Ruislip Gardens where flooding was widespread, the investigation found that the 
drainage network was defective and likely contributed to the flooding.   
 
Recommendations 
 
15. As a consequence of the investigation, a number of recommendations have been made 
across the impacted catchments [NB the areas have been established through previous 
flood risk strategy plans  and are linked to drainage catchments .  These cover a broad 
scope and have been given identification markers specific to this investigation for 
reference.  A map of the catchments is included in Appendix A of the Investigation]: 
 
 
Catchment 2 – Bessingby Park Area 
1 Hillingdon Council Flood Officers should conduct a review of the flood alleviation works in 
Bessingby Park, ensuring that the basins are working as designed. 
2 Hillingdon Council Flood Officers should facilitate the formation of a Flood Action Group 
(FLAG) at Whitby Road which may increase community flood resilience. 
3 Hillingdon Council Flood Officers should further investigate the mechanisms of the fluvial 
flooding along Whitby Road and undertake remedial action if necessary. 
4 
Hillingdon Highways Team should consider reprofiling works and the installation of 
additional gullies along Beech Avenue to reduce the risk of flooding to properties from the 
highway. 
5 
Flood-affected residents should consider installing Property Flood Resilience (PFR) 
measures to reduce the amount of floodwater entering their property during a flood event. 
The National Flood Forum has a six-step guide to navigate the process of installing PFR 
measures. 
6 
Hillingdon Council Flood Officers should investigate options for further flood alleviation 
works in Bessingby Park and bid for future funding opportunities (where available) should a 
feasible option be identified. 
 
Catchment 4 – Breakspear Road South, Ruislip 
7 
Flood-affected residents should consider installing PFR measures to reduce the amount of 
floodwater entering their property during a flood event. The National Flood Forum has a six-
step guide to navigate the process of installing PFR measures. 

 
 
 
 
 
 
 
Cabinet Member Report – 10 October 2025  Page 6 
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8 Hillingdon Council should continue to review HS2 plans, ensuring that the development 
does not increase the risk of flooding to surrounding properties. 
 
Catchment 5 – East of Ickenham 
9 
Flood-affected residents should consider installing PFR measures to reduce the amount of 
floodwater entering their property during a flood event. The National Flood Forum has a six-
step guide to navigate the process of installing PFR measures. 
10 Breakspear School should investigate the installed drainage of the artificial playing pitch to 
confirm the system is working in line approved drainage plans. 
11 
Hillingdon Council Flood Officers should investigate options for SuDS at Breakspear School 
and bid for future funding opportunities (where available), such as SuDS in Schools grants, 
should a feasible option be identified. 
 
Catchment 6 – West Ruislip Depot Area 
12 
Flood-affected residents should consider installing PFR measures to reduce the amount of 
floodwater entering their property during a flood event. The National Flood Forum has a six-
step guide to navigate the process of installing PFR measures. 
13 
Hillingdon Council Flood Officers should investigate options for SuDS at Glebe Primary 
School and bid for future funding opportunities (where available), such as SuDS in Schools 
grants, should a feasible option be identified. 
14 The EA should consider installing river level or flow gauges on the Ickenham Stream as there 
is no gauge currently within this river. 
 
Catchment 12 – Ruislip Gardens 
15 
Hillingdon Highway Team should review the way the highways drain along Stafford Road, 
Trevor Crescent, Bedford Road, Clyfford Road, and Lea Crescent and consider installing 
additional gullies, rain gardens, or drainage channels along the route to reduce the risk of 
flooding to properties from the highway. 
16 TfL should explore the installation of additional gullies along West End Road to reduce the 
risk of flooding to properties from the highway. 
17 Hillingdon Council should continue to develop the surface water sewer daylighting scheme 
at Bridgewater Road Playing Fields with support from TWUL. 
18 Hillingdon Council Flood Officers should facilitate the formation of a FLAG at Clyfford Road 
and surrounding area, with the aim of increasing community flood resilience. 
19 
Flood-affected residents should consider installing PFR measures to reduce the amount of 
floodwater entering their property during a flood event. The National Flood Forum has a six-
step guide to navigate the process of installing PFR measures 

 
 
 
 
 
 
 
Cabinet Member Report – 10 October 2025  Page 7 
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20 Hillingdon Council Flood Officers should continue to work in partnership with the EA to 
develop the Ruislip Gardens flood alleviation scheme towards implementation. 
 
Catchment 17 – Victoria Road Area 
21 TWUL should investigate a possible misconnection in their network upstream of Bourne 
Primary School. 
22 
Hillingdon Council Flood Officers should engage with Bourne Primary School’s maintenance 
team to conduct a drainage survey in order to better understand the drainage issues at the 
site. 
23 
Hillingdon Council Flood Officers should engage with Bourne Primary School to develop a 
flood action plan based on findings from the drainage survey and an understanding of how 
the site floods. 
24 
Flood-affected residents should consider installing PFR measures to reduce the amount of 
floodwater entering their property during a flood event. The National Flood Forum has a six-
step guide to navigate the process of installing PFR measures. 
25 
Hillingdon Council Flood Officers should investigate options for drainage improvements at 
Bourne Primary School and bid for future funding opportunities (where available), such as 
SuDS in Schools grants, should a feasible option be identified. 
26 Hillingdon Council and Harrow Council should collaborate to investigate opportunities for a 
flood alleviation scheme within this catchment. 
27 Lead Local Flood Authority officers should support investigate and support authorities with 
the implementation of flood resilience measures at Queensmead School. 
28 Lead Local Flood Authority officers should continue to work in partnership with the EA and 
TWUL to develop the Victoria Road flood alleviation scheme towards implementation. 
 
Catchment 26 – Brook Drive, Ruislip 
29 
Lead Local Flood Authority officers should continue to work in partnership with the EA to 
develop the Pinn Meadows and Park Wood SSSI Natural Flood Management schemes 
towards implementation. 
30 
Flood-affected residents should consider installing PFR measures to reduce the amount of 
floodwater entering their property during a flood event. The National Flood Forum has a six-
step guide to navigate the process of installing PFR measures. 
 
Catchment 44 – West End Road 
31 Hillingdon Highways Team should consider installing additional gullies along Cherry Close 
and Eversley Crescent to reduce the risk of flooding to properties from the highway. 

 
 
 
 
 
 
 
Cabinet Member Report – 10 October 2025  Page 8 
(Part 1 Public) 
32 TWUL should investigate their surface water sewer system at Cherry Close and rectify any 
blockages and consider improvements in capacity. 
33 
Flood-affected residents should consider installing PFR measures to reduce the amount of 
floodwater entering their property during a flood event. The National Flood Forum has a six-
step guide to navigate the process of installing PFR measures. 
34 Hillingdon Council and TWUL should collaborate to investigate opportunities for highway 
drainage improvements within the catchment. 
 
16. A number of these actions have already been commenced as part of the day -to-day 
services of the Lead Local Flood Authority.   
 
Status of the Investigation 
 
17. The Investigation has been compiled by the LLFA based on evidence collated including a 
call for evidence from the public and through interviews with key partners .  It is not a 
consultation document.  It sets out recommendations which officers will continue to liaise 
with the various parties identified.   
 
Financial Implications  
  
There are no direct financial implications to the Council associated with the recommendations in 
this report.  
 
RESIDENT BENEFIT & CONSULTATION 
 
The benefit or impact upon Hillingdon residents, service users and communities? 
 
The Investigation is intended to ensure that residents can be better protected from flooding in the 
future.  It identifies actions and work that can be undertaken to achieve that and forms a 
framework for better flood risk management.   
 
Consultation & Engagement carried out (or required) 
 
The Investigation is not a consultation document.  However, it has been compiled on the back of 
a collation of evidence directly from residents and other statutory bodies.  It has only been 
possible due to the engagement from impacted residents.   
 
Officers are fully aware of the stress and disturbance to residents and communities.  Officers are 
therefore extremely grateful to all those who inputted into the investigation despite, in many 
instances, the impacts of the flooding still being felt so forcibly.   
 
 
 
 
 
 

 
 
 
 
 
 
 
Cabinet Member Report – 10 October 2025  Page 9 
(Part 1 Public) 
CORPORATE CONSIDERATIONS 
 
Corporate Finance 
 
Corporate Finance have reviewed this report and concur with the Financial Implications set out 
above, noting there are no direct financial implications associated with the recommendations 
contained in this report. 
 
Legal 
 
Legal Services has considered the content of this report and is satisfied that section 19 of the 
Flood and Water Management Act 2010 (“the Act”) confers a duty on the Council as a lead local 
authority to investigate flooding incidents within its area. However, the Council is also afforded 
discretion as to the extent to which it may consider it necessary or appropriate to investigate 
incidents of flooding in its area.  
  
The Act confers a further duty on the Council to publish the results of its investigation and notify 
any other risk management authorities.  
  
In considering publication of data within its flood investigation report, the Council must adhere to 
data protection legislation (UK GDPR and Data Protection Act 2018) and where necessary obtain 
advice from the Council’s Information Governance Legal Services Team. 
 
BACKGROUND PAPERS 
 
NIL 
 
TITLE OF ANY APPENDICES 
 
NIL 

23 September 2024 Flood Event   1 
 
 
Section 19 Flood Investigation 
 
23 September 2024 Flood Event 


23 September 2024 Flood Event   2 
 
Acknowledgements 
We would like to extend our heartfelt thanks to all those who participated in the recent 
flood investigation, especially the residents who experienced flooding firsthand.  Flooding is 
a deeply distressing event, bringing disruption, damage, and emotional strain. We recognise 
the significant impact it has on individuals, families, and communities. 
We are especially grateful to those who, despite the stress and difficulty of their 
circumstances, provided valuable input to the investigation. Your contributions are essential 
in helping us understand the effects of flooding and to inform improved flood risk 
management for our communities. 
Executive Summary 
This flood investigation report was written as part of the London Borough of Hillingdon 
Council’s (Hillingdon Council) duty as a Lead Local Flood Authority (LLFA) under Section 19 of 
the Flood and Water Management Act 2010 (FWMA). Heavy rainfall on the 22 and 23 
September 2024 caused flooding and disruption across the south-east of England and 
London, including the London Borough of Hillingdon (Hillingdon). There were 172 flood 
incidents reported in total as a result of the rainfall event. This included 123 reports of 
internal flooding and 49 reports of external flooding. The majority of the flood incidents 
were located in Ickenham and Ruislip.  
The investigation aims to identify the sources and causes of the flooding, as well as the flood 
management responsibilities of the Risk Management Authorities (RMAs) and other relevant 
stakeholders involved. Based on these details, this report includes recommendations with 
the aim of reducing the risk of future flood events. 
As part of this investigation, the reported flood incidents were mapped within the 
hydrological catchments set out in Hillingdon Council’s Catchment Plan 2022. The flood 
mechanisms of catchments that contained more than one internal flooding event were 
analysed to identify the sources and causes of flooding on the 23 September 2024. This 
included the use of available data from Thames Water Utilities Limited (TWUL), the 
Environment Agency (EA), and British Geological Survey (BGS), and a site visit to each 
location. The analysis also considered actions taken by each RMA before, during, and after 
the event up to March 2025.  
During the event, the River Pinn, Ickenham Stream, and Yeading Brook experienced high 
water levels that rose above surface water drainage outlets. This reduced the surface water 
sewer network’s ability to discharge into the rivers, limiting its capacity to accommodate 
more flows. The result was that the drainage network became overwhelmed and caused 
surcharging. Locations at the low topographical points were particularly susceptible to 
surface water accumulation. Some of the flood incidents were caused or worsened by fluvial 
flooding from the River Pinn or the Yeading Brook.   

23 September 2024 Flood Event   3 
 
List of Recommendations 
Catchment 2 – Bessingby Park Area 
1 Hillingdon Council Flood Officers should conduct a review of the flood alleviation works in 
Bessingby Park, ensuring that the basins are working as designed. 
2 Hillingdon Council Flood Officers should facilitate the formation of a Flood Action Group 
(FLAG) at Whitby Road which may increase community flood resilience. 
3 Hillingdon Council Flood Officers should further investigate the mechanisms of the fluvial 
flooding along Whitby Road and undertake remedial action if necessary. 
4 Hillingdon Highways Team should consider reprofiling works and the installation of additional 
gullies along Beech Avenue to reduce the risk of flooding to properties from the highway. 
5 
Flood-affected residents should consider installing Property Flood Resilience (PFR) measures 
to reduce the amount of floodwater entering their property during a flood event. The National 
Flood Forum has a six-step guide to navigate the process of installing PFR measures. 
6 
Hillingdon Council Flood Officers should investigate options for further flood alleviation works 
in Bessingby Park and bid for future funding opportunities (where available) should a feasible 
option be identified. 
 
Catchment 4 – Breakspear Road South, Ruislip 
7 
Flood-affected residents should consider installing PFR measures to reduce the amount of 
floodwater entering their property during a flood event. The National Flood Forum has a six-
step guide to navigate the process of installing PFR measures. 
8 Hillingdon Council should continue to review HS2 plans, ensuring that the development does 
not increase the risk of flooding to surrounding properties. 
 
Catchment 5 – East of Ickenham 
9 
Flood-affected residents should consider installing PFR measures to reduce the amount of 
floodwater entering their property during a flood event. The National Flood Forum has a six-
step guide to navigate the process of installing PFR measures. 
10 Breakspear School should investigate the installed drainage of the artificial playing pitch to 
confirm the system is working in line approved drainage plans. 
11 
Hillingdon Council Flood Officers should investigate options for SuDS at Breakspear School 
and bid for future funding opportunities (where available), such as SuDS in Schools grants, 
should a feasible option be identified. 
 
Catchment 6 – West Ruislip Depot Area 
12 
Flood-affected residents should consider installing PFR measures to reduce the amount of 
floodwater entering their property during a flood event. The National Flood Forum has a six-
step guide to navigate the process of installing PFR measures. 

23 September 2024 Flood Event   4 
 
13 
Hillingdon Council Flood Officers should investigate options for SuDS at Glebe Primary 
School and bid for future funding opportunities (where available), such as SuDS in Schools 
grants, should a feasible option be identified. 
14 The EA should consider installing river level or flow gauges on the Ickenham Stream as there is 
no gauge currently within this river. 
 
Catchment 12 – Ruislip Gardens 
15 
Hillingdon Highway Team should review the way the highways drain along Stafford Road, 
Trevor Crescent, Bedford Road, Clyfford Road, and Lea Crescent and consider installing 
additional gullies, rain gardens, or drainage channels along the route to reduce the risk of 
flooding to properties from the highway. 
16 TfL should explore the installation of additional gullies along West End Road to reduce the risk 
of flooding to properties from the highway. 
17 Hillingdon Council should continue to develop the surface water sewer daylighting scheme at 
Bridgewater Road Playing Fields with support from TWUL. 
18 Hillingdon Council Flood Officers should facilitate the formation of a FLAG at Clyfford Road 
and surrounding area, with the aim of increasing community flood resilience. 
19 
Flood-affected residents should consider installing PFR measures to reduce the amount of 
floodwater entering their property during a flood event. The National Flood Forum has a six-
step guide to navigate the process of installing PFR measures 
20 Hillingdon Council Flood Officers should continue to work in partnership with the EA to 
develop the Ruislip Gardens flood alleviation scheme towards implementation. 
 
Catchment 17 – Victoria Road Area 
21 TWUL should investigate a possible misconnection in their network upstream of Bourne 
Primary School. 
22 
Hillingdon Council Flood Officers should engage with Bourne Primary School’s maintenance 
team to conduct a drainage survey in order to better understand the drainage issues at the 
site. 
23 
Hillingdon Council Flood Officers should engage with Bourne Primary School to develop a 
flood action plan based on findings from the drainage survey and an understanding of how the 
site floods. 
24 
Flood-affected residents should consider installing PFR measures to reduce the amount of 
floodwater entering their property during a flood event. The National Flood Forum has a six-
step guide to navigate the process of installing PFR measures. 
25 
Hillingdon Council Flood Officers should investigate options for drainage improvements at 
Bourne Primary School and bid for future funding opportunities (where available), such as 
SuDS in Schools grants, should a feasible option be identified. 
26 Hillingdon Council and Harrow Council should collaborate to investigate opportunities for a 
flood alleviation scheme within this catchment. 

23 September 2024 Flood Event   5 
 
27 Lead Local Flood Authority officers should support investigate and support authorities with 
the implementation of flood resilience measures at Queensmead School. 
28 Lead Local Flood Authority officers should continue to work in partnership with the EA and 
TWUL to develop the Victoria Road flood alleviation scheme towards implementation. 
 
Catchment 26 – Brook Drive, Ruislip 
29 
Lead Local Flood Authority officers should continue to work in partnership with the EA to 
develop the Pinn Meadows and Park Wood SSSI Natural Flood Management schemes 
towards implementation. 
30 
Flood-affected residents should consider installing PFR measures to reduce the amount of 
floodwater entering their property during a flood event. The National Flood Forum has a six-
step guide to navigate the process of installing PFR measures. 
 
Catchment 44 – West End Road 
31 Hillingdon Highways Team should consider installing additional gullies along Cherry Close 
and Eversley Crescent to reduce the risk of flooding to properties from the highway. 
32 TWUL should investigate their surface water sewer system at Cherry Close and rectify any 
blockages and consider improvements in capacity. 
33 
Flood-affected residents should consider installing PFR measures to reduce the amount of 
floodwater entering their property during a flood event. The National Flood Forum has a six-
step guide to navigate the process of installing PFR measures. 
34 Hillingdon Council and TWUL should collaborate to investigate opportunities for highway 
drainage improvements within the catchment. 
 
 
  

23 September 2024 Flood Event   6 
 
Contents 
1 Introduction ........................................................................................................................ 8 
2 Risk Management Authorities .......................................................................................... 12 
3 Flood Incident Details ....................................................................................................... 16 
4 Flood Event Analysis ......................................................................................................... 26 
5 Catchment 2 – Bessingby Park Area, Ruislip .................................................................... 28 
6 Catchment 4 – Breakspear Road South, Ickenham .......................................................... 36 
7 Catchment 5 – East of Ickenham ...................................................................................... 42 
8 Catchment 6 – West Ruislip Depot Area .......................................................................... 49 
9 Catchment 12 – Ruislip Gardens ...................................................................................... 57 
10 Catchment 17 – Victoria Road Area ............................................................................. 66 
11 Catchment 26 – Brook Drive, Ruislip ........................................................................... 74 
12 Catchment 44 – West End Road, Ruislip ...................................................................... 82 
13 Post Flooding Observations ......................................................................................... 91 
14 General Recommendations ......................................................................................... 93 
15 Flooding Incidents Outside the Section 19 Criteria ..................................................... 95 
16 Before, during and after the Event .............................................................................. 96 
17 Appendix A ................................................................................................................. 100 
 
 
 
 

23 September 2024 Flood Event   7 
 
Acronyms and Abbreviations 
Abbreviation  Definition 
BGS British Geological Survey 
CDA Critical Drainage Area 
DfE Department for Education 
DWMP Drainage and Wastewater Management Plan 
EA Environment Agency 
FLAG Flood Action Group 
FWMA Flood and Water Management Act 
LFB London Fire Brigade 
LFRMS Local Flood Risk Management Strategy 
LiDAR Light Detection and Ranging 
LLFA Lead Local Flood Authority  
MAFP Multi-Agency Flood Plan 
Harrow London Borough of Harrow 
Hillingdon London Borough of Hillingdon 
Hillingdon Council London Borough of Hillingdon Council 
HS2 High Speed 2 
PFR Property Flood Resilience 
RMA Risk Management Authority 
RoFSW Risk of Flooding from Surface Water 
SuDS Sustainable Drainage Systems 
TfL Transport for London 
TWUL Thames Water Utilities Limited 

23 September 2024 Flood Event   8 
 
1 Introduction 
1.1 Background Policy and Information 
1.1.1 This flood investigation report has been prepared by Metis Consultants Ltd on behalf of the 
London Borough of Hillingdon Council (Hillingdon Council) as part of their duty as a Lead 
Local Flood Authority (LLFA). Under Section 19 of the Flood and Water Management Act 
2010 (FWMA), LLFAs are required to investigate significant flooding incidents and publish 
the results. 
1.1.2  As stipulated by Section 19, Hillingdon Council must, to the extent that they consider it 
necessary or appropriate, investigate: 
• which Risk Management Authorities (RMAs) have relevant flood risk management 
functions, and 
• whether each of those RMAs has exercised, or is proposing to exercise, those functions in 
response to the flood. 
1.1.3 After completing the flood investigation, Hillingdon Council must publish the results of its 
investigation and notify the relevant RMAs. 
1.1.4 The criteria of flooding that triggers a Section 19 investigation is set by each LLFA for their 
area. At the time of writing, the criteria for Hillingdon Council are where more than 10 
properties suffer internal flooding. 
1.1.5 The flooding event on the 23 September 2024 triggered a Section 19 investigation, as there 
was internal flooding to more than 10 properties. A total of 172 flood incidents were 
reported regarding this flooding event, including 123 internal flooding incidents and 49 
external flooding incidents. 157 of these flood incidents were reported directly to 
Hillingdon Council, with the Environment Agency (EA) sharing two additional reports of 
flooding, and the London Fire Brigade (LFB) sharing 13 additional reports of flooding. The 
majority of the flooding reports came from either Ickenham or Ruislip.  It is possible more 
properties flooded given there is an acknowledged under reporting of flood incidents.   
1.2 Methodology 
1.2.1 To conduct the investigation, data was collected from the relevant RMAs through a series 
of emails and interviews. The source and data received is outlined in Table 1-1.  
 
  

23 September 2024 Flood Event   9 
 
Table 1-1: Data sources. 
Source Data 
Hillingdon Lead Local Flood 
Authority officers 
• Flooding reports 
• Photographs and videos of the event 
• Historical flood records 
• Hydrological catchment mapping 
Hillingdon Highways Team • Actions taken before, during or after the event 
• Formal view on the causes of the flooding 
Hillingdon Emergency 
Planning and Response Team 
• Actions taken before, during or after the event 
• Formal view on the causes of the flooding 
Thames Water Utilities 
Limited (TWUL) 
• Actions taken before, during or after the event 
• Flooding reports 
• Sewer network data 
• Formal view on the causes of the flooding 
Internally flooded schools  
• Actions taken before, during or after each event 
• Photographs and videos of the event 
• Formal view on the causes of the flooding 
EA 
• Actions taken before, during or after each event 
• Flooding reports 
• Rainfall data 
• Flood Alert data 
• Detailed River Network data 
• Mapping of flood risk from different sources 
• River level data 
• Light Detection and Ranging (LiDAR) data 
• Formal view on the causes of the flooding 
LFB • Actions taken before, during or after each event 
• Flooding reports 
London Borough of Harrow 
(Harrow) LLFA 
• Actions taken after the event 
• Formal view on the causes of the flooding 
 
Community Engagement and Evidence Collection 
1.2.2 To support a comprehensive understanding of the September 2024 flooding event, the 
Council launched a public-facing questionnaire, which was made available on the Council’s 
website from 3 December 2024 to 12 January 2025. The purpose of this survey was to 
gather first-hand accounts from residents affected by flooding, enabling the Council to 
collect qualitative and quantitative data to inform its investigation. 
1.2.3 The questionnaire included structured questions regarding the timing, location, and 
severity of flooding, as well as open-ended sections for residents to describe their 
experiences in more detail. Crucially, respondents were also given the opportunity to 
upload photographs and videos, which provided valuable visual evidence of flood impacts 

23 September 2024 Flood Event   10 
 
and water flow patterns. In total, 152 responses were received, representing a significant 
portion of affected communities and contributing to a more nuanced understanding of the 
event. 
1.2.4 The online surveys were supplemented by interviews and direct engagement with other 
risk management authorities and representatives from educational facilities that 
experienced flooding.   
Data Integration and Catchment Analysis 
1.2.5 To provide further context to the community feedback, the Council undertook a detailed 
mapping exercise using Geographical Information Systems (GIS). This involved the 
integration of historical flood records, topographical data, and drainage infrastructure 
information to identify potential sources of flood risk within each impacted hydrological 
catchment. 
1.2.6 Following this desktop analysis, a targeted site visit was conducted on 7 April 2025 to 
validate the mapped data and observe physical features that may have influenced flood 
behaviour. This included inspecting watercourses, culverts, surface water flow paths, and 
areas of known drainage constraint. The visit provided critical insight into the mechanisms 
that contributed to flooding, such as blocked assets, overland flow routes, and 
topographical depressions. 
Supplementary Site Investigations and Stakeholder Engagement 
1.2.7 Further site inspections were carried out during Summer 2025, focusing on sensitive and 
high-risk locations, particularly Bessingby Park and Ruislip Gardens, where flood impacts 
were notably severe. These visits allowed officers to assess seasonal conditions, vegetation 
growth, and any interim changes to land use or drainage systems that may affect future 
flood risk. 
1.2.8 In parallel, the Council maintained ongoing liaison with key stakeholders, including officers 
from the Environment Agency and Thames Water, to share findings, validate assumptions, 
and ensure alignment with statutory responsibilities. These discussions helped clarify asset 
ownership, operational responses, and future maintenance commitments. 
Review of Risk Management Authority Responsibilities and Actions 
1.2.9 As part of the investigation, the Council undertook a detailed review of the roles and 
responsibilities of each Risk Management Authority (RMA) under the Flood and Water 
Management Act 2010. This included evaluating the actions taken by each RMA before, 
during, and after the September 2024 flood event. 
Conclusions and Recommendations 
1.2.10 The findings of this multi-faceted investigation have been compiled and presented in this 
report. Based on the evidence gathered, including resident feedback, site observations, GIS 

23 September 2024 Flood Event   11 
 
analysis, and stakeholder input, a series of recommendations for flood risk mitigation have 
been developed.  These recommendations aim to: 
• Address identified vulnerabilities in drainage and surface water management. 
• Improve inter-agency coordination and emergency response protocols. 
• Enhance community awareness and preparedness for future flood events. 
• Support investment in infrastructure upgrades and natural flood management 
solutions. 
1.2.11 The Council will continue to work collaboratively with RMAs and local stakeholders to 
implement these recommendations and reduce flood risk across the borough. 

23 September 2024 Flood Event   12 
 
2 Risk Management Authorities 
2.1 Introduction 
2.1.1 There are multiple RMAs who hold responsibilities for managing the risks of flooding 
within Hillingdon. These are shown in Table 2-1. The responsibilities of other key 
stakeholders related to the flooding event are outlined in Table 2-2. 
Table 2-1: Relevant RMAs. 
RMA  Borough-specific 
authority 
Flood risk management responsibilities 
EA EA Main rivers and reservoirs 
LLFA Hillingdon Council Surface water, ordinary watercourses, and 
groundwater 
Water & Sewerage 
Company TWUL Surface water, foul & combined sewer systems 
Highway Authority Hillingdon Council Public highway drainage 
Highway Authority Transport for London 
(TfL) Highway drainage on A roads 
Highway Authority National Highways Responsible for the Strategic Road Network 
 
Table 2-2: Relevant stakeholders. 
Stakeholder  Flood risk management responsibilities 
LFB Responding to emergency calls related to flooding 
Hillingdon Emergency Planning and 
Response Team 
Responding to emergency calls related to flooding, 
produce a MAFP 
Harrow LLFA Surface water, ordinary watercourses, and groundwater 
within Harrow 
Bourne Primary School Maintaining the onsite surface water sewer network 
Queensmead School Maintaining the onsite surface water sewer network 
 
2.2 Environment Agency (EA) 
2.2.1 The EA is the national flood risk authority for England and Wales. They are responsible for 
managing the risk of flooding from main rivers, reservoirs, estuaries and the sea. In the 
borough, the EA has an important role in working with other RMAs to manage the risk of 
flooding from rivers and reservoirs and advising Local Planning Authorities on how 
development proposals may influence and be influenced by fluvial flood risk. They take 
part in emergency planning through issuing Flood Alerts and being a Category One 
Responder to flooding events under the Civil Contingencies Act 2004. 

23 September 2024 Flood Event   13 
 
2.2.2 The Main Rivers within Hillingdon that the EA have oversight of are shown within the EA’s 
Statutory Main River online mapping and listed below:  
• Duke of Northumberland’s River • Ickenham Stream • River Pinn 
• River Colne • Frays River • River Crane 
• Wraysbury River • Cannon Brook • Bigley Ditch 
• Yeading Brook (the West and East 
arms) 
• River Crane 
2.2.3 The River Pinn, Ickenham Stream, and Yeading Brook run through the catchments that 
were affected by the September 2024 flood event.  
2.3 Hillingdon Council 
2.3.1 Hillingdon Council has multiple duties to perform as an RMA due to its role as a LLFA, 
Highway Authority, and Category One Responder. The LLFA leads on managing the risk of 
flooding from surface water, groundwater, and ordinary watercourses. Other duties of the 
LLFA are outlined below under the different acts: 
• Flood and Water Management Act 2010 
• Develop, maintain, apply, and monitor a Local Flood Risk Management Strategy (LFRMS) 
(Section 9) 
• Carry out flood risk investigations upon coming aware of a flood in its area (Section 19) 
• Establish and maintain a register of structures or features which are likely to have a 
significant effect on a flood risk in its area (Section 21) 
 
• Land Drainage Act 1991 
• Carry out flood risk management work if the work is considered desirable with regards to 
the LFRMS for the area, and the purpose of the work is to manage flood risk in the 
authority’s area from surface runoff or groundwater (Section 14A) 
• Regulate the flow of ordinary watercourses by prohibiting obstructions on ordinary 
watercourses and requiring works for maintaining the flow of an ordinary watercourse 
(Sections 23 and 25) 
 
• Town and Country Planning Order 2015 
• Undertake a statutory consultee role on surface water drainage proposals for major 
developments 
 

23 September 2024 Flood Event   14 
 
• Flood Risk Regulations 2009 
• Prepare a preliminary assessment report in relation to flooding in its area (Section 10) 
• Identify flood risk areas (Section 14) 
• Prepare flood hazard maps and flood risk maps in relation to each relevant flood risk area 
(Section 19) 
2.3.2 Other RMAs have a duty to cooperate with LLFAs to undertake the above responsibilities. 
The LLFA can also carry out work in collaboration with other RMAs to help alleviate 
flooding within the borough.  
2.3.3 As a Highway Authority, Hillingdon Council are responsible for providing and managing 
highways assets that are not privately owned, nor managed by TfL or National Highways. 
TfL managed routes in Hillingdon are the A4, A30, A40, A312, A437, and A4180. National 
Highways managed routes in Hillingdon are the M4 and M40. As part of Hillingdon 
Council’s responsibilities for their highway assets, they must minimise the risk of highway 
flooding and maintain gullies and drains that run beneath the roads and footpaths. 
2.3.4 As a landowner, Hillingdon Council have a responsibility to safeguard their own land and 
property against flooding. Common Law also requires Hillingdon Council to carry out tasks, 
such as drain clearing and maintaining existing flood defences, so that they do not increase 
the risk of flooding to any neighbouring properties.  
2.3.5 As a Category One Responder under the Civil Contingencies Act 2004, Hillingdon Council 
plays a lead role in emergency planning and recovery after a flood event. The Council is 
required to produce a Multi-Agency Flood Plan (MAFP), outlining delivery of the 
emergency response to a flood and co-ordinates all relevant stakeholders, including other 
Category One Responders. 
2.4 Thames Water Utilities Limited 
2.4.1 TWUL are the sewerage provider for the borough, as well as a supplier of clean water in 
the borough along with Affinity Water. TWUL have responsibility for the management of 
flood risk in relation to the drainage network. Under Section 94 of the Water Industry Act 
1991, TWUL must construct and maintain their sewers ensuring sufficient performance 
under all normal local climatic conditions. This includes managing any potential failures of 
their infrastructure that may cause flooding and ensuring sufficient maintenance of public 
sewers is carried out to reduce the risk of sewer flooding. They are a Category Two 
Responder under the Civil Contingencies Act 2004.  
2.4.2 As part of their responsibility for ensuring flood resilience, TWUL have developed a 25 year 
Drainage and Wastewater Management Plan (DWMP) to reduce pressures on the service, 
including reducing the number of residential properties that are at risk of flooding. 

23 September 2024 Flood Event   15 
 
2.5 Key Stakeholders 
2.5.1 There are several other key stakeholders related to the flooding event, including 
landowners, Category One Responders, and Harrow LLFA, that do not act as RMAs for 
Hillingdon. 
Landowners 
2.5.2 Landowners have the primary responsibility of protecting their own land and property, 
including private roads, against flooding. Under Common Law, they are required to ensure 
any developments to their land or property do not increase the risk of flooding to a 
neighbouring property.  
2.5.3 Riparian landowners, meaning those who own land that includes a watercourse, are 
responsible for ensuring any structures within the watercourse are clear of debris and the 
watercourse is able to flow naturally. Riparian landowners are also responsible for 
maintaining the bed and banks of the watercourse.  
2.5.4 Hillingdon Council and TfL are major landowners that were impacted by the September 
2024 flooding event. They also act as riparian owners for stretches of the River Pinn, 
Ickenham Stream, and Yeading Brook. 
Category One Responders 
2.5.5 All local authorities and blue light emergency

View Decision / Minutes Text

Executive Decision Notice – 09 December 2025  
 
This notice is a public document also available to view on the Council's website www.hillingdon.gov.uk  
OFFICIAL EXECUTIVE DECISION NOTICE  
PUBLISHED BY DEMOCRATIC SERVICES 
 
 
Notice is hereby given that the following decision(s) have been made today by 
Cabinet Members at the London Borough of Hillingdon: 
 
Title of decision OUTCOME OF CONSULTATION ON A POTENTIAL 7.5T 
WEIGHT RESTRICTION ON HOWLETT’S LANE AND 
SURROUNDING ROADS 
Reference No. 1584 
Date of decision Tuesday 09 December 2025  
Call-in expiry date Tuesday 16 December 2025 
Relevant Select 
Committee 
Corporate Resources & Infrastructure Select Committee 
Relevant Wards Ruislip  
 
Decision made 
 
Cabinet Members making 
the decision 
Councillor Steve Tuckwell  - Cabinet Member for Planning, 
Housing & Growth 
Decision That the Cabinet Member for Planning, Housing & 
Growth: 
 
1) Noted the low response rate to the 
consultation of just 2.3%;  
 
2) Considered that all responses reported were 
for the introduction of the proposed 7.5T 
weight limit in the area, and generally positive 
feedback had been received as detailed in the 
report; and 
 
3) Due to the road safety and residential benefit 
of introducing the restriction, instruct ed 
officers to proceed with seeking HS2 funding 
for the implementation of the scheme.    
 
Reason for decision The recommendations set out in this report allow for the 
scheme to be progressed to benefit road safety and to 
improve environmental conditions for the residents.  
Alternative options 
considered and rejected 
None at this stage.  
 
Classification Part I – Public 
Link to associated report  Here 
 
Relevant Officer contact 
& Directorate 
Sophie Wilmot – Residents Services Directorate 


Executive Decision Notice – 09 December 2025  
 
This notice is a public document also available to view on the Council's website www.hillingdon.gov.uk  
Any interest declared by 
the Cabinet Member(s) / 
dispensation granted  
N/A 
 
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decision be 
implemented by 
officers? 
Officers can implement Cabinet Member decision in this notice only 
from the expiry of the scrutiny call-in period which is: 
 
5pm on Tuesday 16 December 2025  
 
However, this is subject to the decision not being called in by 
Councillors on the relevant Select Committee. Upon receipt of a 
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to Information) (England) Regulations 2012. 
 
This is the formal notice by the Council of the above executive 
decision, including links to the reports where applicable.  
 
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Democratic Services on 01895 250636 or email: 
democratic@hillingdon.gov.uk.  
 
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Council’s website.   
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Hillingdon Council Cabinet Member and Officer Decisions

SECTION 19 FLOOD INVESTIGATION: SEPTEMBER 2024 FLOOD EVENT

Report Document

Decision / Minutes Document

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