Flash floods last summer not made worse by drain issues, report finds

The flood caused an estimated £16million in damage to almost 250 properties
By Local Democracy Reporter Josh Mellor

Flooding in Brooke Road, Walthamstow (Credit: Twitter/@TheOneException)
Flooding in Brooke Road, Walthamstow (Credit: Twitter/@TheOneException)

A newly published report on the floods that devastated the borough last year argues they were not made worse by any problem with the drains. 

The report, published by Waltham Forest Council, examines the floods last summer, which caused a power cut at Whipps Cross Hospital and an estimated £16million in damage.

The report notes the worst flood, on 25th July, was caused by a “once in 170 years” storm that saw 80mm of rainfall in one day and flooded almost 250 properties.

It argues that the “fundamental problem” was that the amount of rainfall “substantially exceeded” the level Thames Water’s drains were designed to cope with, rather than any issue with the drains or their maintenance.

The report states: “Under normal rainfall conditions, highway gullies within the borough would collect surface water run-off and convey these flows into the Thames Water sewer system. 

“Given the sheer volume of rainfall that was received in such a short space of time, it is evident that both the surface water sewer system and the highway drainage would have reached capacity extremely quickly.

“It is also likely that there would have been increased overland flows in many places, where surface water could not access the drainage systems as it would normally.”

Although the report recommends a review of the council’s “gully cleansing operations and frequencies”, it does not explore whether blocked gullies could have made the floods worse.

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Plants growing out of a blocked street drain on Milton Road

However residents of Wood Street and Whipps Cross, whose views are included in the report, say some gullies and sewers in their areas were not “maintained sufficiently” and slowed drainage.

Peterborough Road residents add that their gullies were blocked and “prevented the water draining”, which resulted in higher water levels.

They said: “Gullies were blocked and ineffective, indicating they have not been maintained sufficiently by Waltham Forest Council.

“Main drains were operating at very limited capacity in West End Avenue, likely due to substantial blockage, indicating they had not been maintained sufficiently by Thames Water.”

Wood Street South Flood Action Group, meanwhile, claim there was only one documented maintenance in their area between 2016 and August last year.

Thames Water have commissioned their own independent review into the flooding, examining whether the company met its legal duty to keep London “effectually drained”. Its findings are expected in the first half of this year.

In a published internal review the water company has already recognised that it needs to improve its response to adverse weather warnings, incident response and customer service approach.

A Thames Water spokesperson said: “Since the flooding we have worked closely with Waltham Forest and provided detailed information to help with their report.

“We understand flooding of any kind is a horrible thing for residents and when sewer flooding is reported to us we will do all we can to support our customers.”

Residents can read the council’s full draft report here and are invited to give feedback on the findings by 7th March.

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