Surface water flooding poses a significant threat to property and infrastructure in London. The government think-tank, London Councils, states on their website that: “London is at risk of flooding from several sources, including rivers (fluvial flooding), ground water and surface water. Of all these sources, surface water poses the greatest risk to properties in the city.”

Surface water (or pluvial) flooding occurs when extremely heavy rainfall saturates drainage systems and the excess water can’t be absorbed. In recent years there have been numerous cases of significant surface water floods affecting various parts of the city. We have documented five real-life examples below, comparing the documented floods to flood maps generated by our own Flowroute-i™ flood modelling software. We have also used our software to analyse popular sites in London which, despite no recent documented cases, are at high risk from surface water flooding according to our data. This includes the Bank of England and King’s Cross Station.

The video above shows the chaos caused by surface water floods in Cricklewood, London. The map below shows surface water accumulation areas around Cricklewood station, as modelled by our Flowroute-i technology. The nearest river to Cricklewood station is over 1km away.

Fig. 1 Cricklewood, London – 75yr return period flood event

Major floods affected large parts of the country in 2007. The video above illustrates the disruption caused to roads, shops and residential areas around Croydon that year. Our flood map below, showing the Wandle Park area of Croydon, highlights the significant threat posed by surface water flooding. Again, Wandle Park is almost 1km away from the nearest watercourse.

Fig. 2 Wandle Park, Croydon – 75yr return period flood event

The short video above shows surface water flooding in Bromley, South East London. Our flood map below shows that large residential parts of Bromley, particularly off Queen’s Mead Road, are vulnerable to surface water flooding.

Fig. 3 Bromley, London – 75yr return period flood event

The video above shows the disruption on a major road near Brent Cross, London, caused by surface water flooding. Our flood map below shows that the A41 sits on a surface water floodplain. It also shows that Brent Cross Shopping Centre and the North Circular are also vulnerable to surface water floods.

N.B. Brent Cross also sits on a river floodplain, but our analysis of this video and our data suggests that this particular event is attributable to surface water flooding

Fig. 4 Brent Cross, London – 75yr return period flood event

Although Epsom sits just outside Greater London in Surrey, the case of the Ashley Shopping Centre is worth mentioning as our flood map below shows that only a small area to the south of the centre is at significant risk. However, this is based on a 1 in 75 year return period, meaning the areas identified have a 0.75% chance of being affected by surface water floods in a given year. 2007 saw some of the most extreme flooding to affect the UK in decades, resulting in major surface water floods in areas generally considered to be at lower risk.

Fig. 5 Epsom, Surrey – 75yr return period flood event

We have identified the following five sites in London as vulnerable to surface water flooding, despite no recent documented cases of flooding in these areas.

Our flood maps show that much of the North facing side of the Bank of England sits in a surface water accumulation area.

Fig. 6 Bank of England, London – 75yr return period flood event

Our flood maps show the areas around King’s Cross Station most likely to be affected by surface water flooding. Pancras Road and York Way are particularly vulnerable.

Fig. 7 King’s Cross, London – 75yr return period flood event

Our flood maps show surface water accumulation areas around the North West and East side of the Royal Albert Hall.

Fig. 8 Kensington Gore, London – 75yr return period flood event

The largest commercial centre in London, our flood map below shows significant areas within and around Westfield at risk from surface water flooding.

Fig. 9 Shepperd’s Bush, London – 75yr return period flood event

Extreme and sustained rainfall can potentially disrupt London’s important community services. Our flood map below shows the south and north parts of The Portland Hospital are at risk.

Fig. 10 Portland Hospital, London – 75yr return period flood event

Many people believe that only buildings sitting close to rivers, reservoirs or the sea are at risk from flooding. However, 4 of our 5 documented case studies show multiple surface water flooding events affecting areas which are not close to any watercourses. Our flood data appears to corroborate the fact that these areas are vulnerable to flooding.

Using our Flowroute-i data, we also identified a further 5 sites in London sitting on or very close to surface water accumulation areas. We assume that major public buildings will have adequate flood protection measures in place, however, for private residents living in these areas this may not be the case. To check if your property is at risk from surface water flooding, you can run a fast, free check at: riskcentral.co.uk

If you are interested in accessing our flood data for commercial or non-commercial use, please contact us.