A short while ago, a local resident got in touch to raise the issue of flooding on Chestnut Avenue. In heavy rain the drains reach capacity and overflow, causing flooding on the road, which often reaches people’s gardens and driveways.
Councillor Alexa Micheal raised this with the Neighbourhood Manager at Bromley Council our behalf, and we have received the following response.
Following a joint review with the Council’s Highways and Drainage teams, we have assessed the circumstances contributing to flooding in this location. The properties affected are situated at the bottom of a hill, where surface water naturally converges during periods of heavy rainfall. This places additional pressure on the local surface water sewer operated by Thames Water.
During intense rainfall events, the Thames Water sewer is known to become surcharged, resulting in water being forced back up through highway gullies and manholes – a condition referred to as hydraulic overload. In these situations, the constraint is not the number of gullies or drains on the highway, but the limited downstream capacity of the sewer network itself.
Officers have therefore advised that installing additional gullies or highway drainage assets would not resolve the flooding issue in Chestnut Avenue. As the receiving sewer is already operating at capacity during heavy rain, further connections would not meaningfully reduce flood risk and could, in some circumstances, exacerbate surcharge during peak events.
The Council continues to maintain its highway drainage assets in line with its routine inspection and cleansing programme. Gullies in Chestnut Avenue were last fully cleansed in October 2025, with a further visual inspection undertaken in March 2026 confirming that the system was operational, with only minor surface detritus present.
Given the nature of the problem, the primary constraint remains downstream sewer capacity rather than local highway drainage provision. Where manholes are observed to surcharge during storm conditions, residents are advised to report these incidents directly to Thames Water, as the statutory sewerage undertaker responsible for the network. However, it should be recognised that increasing sewer capacity is a complex undertaking, and improvements are unlikely to be deliverable in the short to medium term.
In light of this, residents have previously been advised to consider proportionate property-level flood protection measures, which may help reduce the risk of water entering individual homes during severe weather events.
The Council will continue to monitor drainage performance in the area as part of its routine maintenance responsibilities, but it is important to be clear that additional highway drainage assets alone cannot resolve flooding that is fundamentally driven by sewer capacity limitations.
While it’s not fantastic news, at least they are continuing to monitor the situation. Please do report issues to Thames Water, and let us know if you would like us to do this too, on your behalf.
Coney Hall Village Residents' Association (CHVRA) 