Agenda item

Ian Thynne, Head of Environmental Specialists, was in attendance to respond to Members’ questions in relation to the Section 19 Flood Investigation report included in the agenda pack.

Members asked what lessons had been learned from the recent increase in flooding incidents, noting that these had been significantly more frequent than in previous years. The Head of Environmental Specialists responded that the primary lesson learned was that flooding had worsened as the climate had continued to change. He stated that the September 2024 events had been among the worst the Borough had experienced, with devastating impacts on residents in areas such as Ruislip and Northwood. Flooding remained an emotive subject because residents could go years without incident and then suddenly face displacement, property loss, and severe distress.

It was explained that the Council had struggled to keep pace with flood?risk management due to ageing drainage infrastructure, limited funding, and complex interactions with Thames Water. As a result, the Council had shifted toward innovative approaches using green spaces to reduce flood risk. Thirteen projects were being delivered through external Environment Agency funding, a significant achievement given the small size of the team. However, much of the Council’s work necessarily remained reactive, given the impossibility of predicting exactly where future flooding would occur. It was noted that, while proactive projects were being implemented in areas identified as vulnerable, flooding often had to occur before intervention could begin. When incidents did occur, the Council acted quickly; for example, after more than 100 properties were flooded at Ruislip Gardens, a flood action group had been established and a project identified to reduce future risk.

Members enquired whether improved funding and monitoring would enable better preparedness and risk prediction. It was confirmed that, while additional information and funding would be helpful, flooding ultimately depended on unpredictable weather conditions. Officers described the extreme rainfall of 2024, equivalent to a month’s worth falling in a single day, which exceeded the design capacity of many local schemes. It was emphasised that forecasting precise impacts was extremely difficult because outcomes depended on seasonal conditions, infrastructure state, and unpredictable variables. It was noted that residents needed clearer information about their flood?risk status and greater encouragement to undertake their own resilience measures.

The Committee Members asked specifically about situations where blocked gullies and drains were contributing to local flooding. They queried whether the Council could recharge Thames Water for the administrative time spent chasing the company to resolve issues for which it was responsible. In response, it was explained that responsibilities were highly fragmented: Council gullies drained into the Thames Water sewer network, which then flowed into rivers managed by the Environment Agency. In practice, disputes frequently occurred over ownership of drainage systems beneath carriageways or at property boundaries. Reports were often passed back and forth between agencies, creating inefficiencies.

It was believed that costs for reporting or chasing Thames Water were not recovered and it was acknowledged that residents often did not understand which authority held responsibility. Engagement with Thames Water was described as difficult because it was required to prioritise spending its customers’ money carefully, while the Council also had statutory duties. The national “common reporting tool,” intended to streamline processes, remained some distance away from implementation.

Councillors sought further clarifications as to whether, in cases where the Council had undertaken work that later proved to be Thames Water’s responsibility, cost recovery was pursued or could be expanded. The Head of Environmental Specialists agreed that this was an important issue and stated that he would raise the matter with the Highways team to provide a more detailed answer on cost?recovery mechanisms. He noted that Thames Water’s operational teams had often been helpful in clearing networks when asked, although strategic cooperation remained challenging.

Councillors queried whether the growing use of concrete in new developments—and the resulting reduction in natural drainage—was being addressed through planning requirements. They proposed measures such as mandating that residents retain part of their front gardens as permeable surfaces. In response, it was clarified that new developments were already required to achieve Greenfield runoff rates and to incorporate sustainable drainage systems. The greater issue was existing dwellings, many of which had paved front gardens and numerous dropped kerbs. These longstanding changes had reduced infiltration capacity across the Borough and formed part of the legacy issues contributing to current flood problems. The Council was therefore focusing on encouraging residents to adopt measures such as water?butt installation to reduce runoff at household level.

Members enquired who was responsible for cleaning canals and rivers, given that residents often dumped large items such as mattresses and pallets in local waterways. It was explained that canals were managed differently from rivers: canals did not generally have floodplains because their water levels were artificially controlled, whereas rivers were managed by the Environment Agency. It was noted that dredging, often requested by residents, was costly and only provided short?term relief before silt re?accumulated. River maintenance responsibilities depended on ownership, and many residents were unaware that they legally owned and were responsible for maintaining sections of watercourses adjoining their properties. This complexity was part of the wider challenge the Council faced in managing local flood risk.

The Chair asked for clarification regarding a historical flood reference in the report and requested that wording be updated. He also sought further clarification as to how flood action groups (FLAGs) would be engaged in a manner that ensured expert voices were heard without overshadowing residents who had concerns but less technical knowledge. The Head of Environmental Specialists stated that flood action groups served as the frontline link with affected communities and that residents’ lived experience was crucial to understanding local flood mechanisms. The value of working with these groups was highlighted, noting that different areas had different histories and patterns of flooding. It was confirmed that engagement would continue to be strengthened to ensure balanced representation and effective collaboration.

Members thanked the Head of Environmental Specialists for his report and for providing acronyms and abbreviations for ease of reference

RESOLVED: That the Residents’ Services Select Committee:

1.    Noted the findings of the Section 19 investigation and the scale of impacts across priority catchments; and

2.    Noted the programme of actions for 2025/26, including targeted drainage improvements, community Flood Action Groups (FLAGs), and collaborative schemes with EA and TWUL.