60 drainage schemes helping fight flooding

The National Trust staff look after the estates of grand country houses across the north of England and the midlands, but had travelled to Sheffield because we’re seen as national experts in the field of sustainable urban drainage schemes, or SUDS.

And SUDS often are fields: on the former Deep Pits waste ground of the Manor, the landscaping over twenty years ago included drainage channels and landscaped wet areas in the new park fields that would collect rainwater run off from nearby estates.

So now the park itself collects dirty surface water off nearby roads, and then cleans it as it runs through the park, passing through reeds, plants and microorganisms that help break down oil and hydrocarbons. The ponds and their plants also capture pollution like oil spills and particles of rubber and metal from car tyres and brakes, and keep them out of the river far below.

There are more than 60 SUDS sites across Sheffield, says Roger Nowell, the city council’s Natural Flood and Water Management Coordinator, who’s been working on the schemes since Manor Fields Park was built in the late 1990s. Many are in parks and green spaces, built thanks to funding from nearby developers who have to pay to handle the drainage of a new estate.

The Grey To Green scheme in the city centre is also a SUDS, retrofitted to help clean surface water and reduce flooding from city streets, as well as improving the look of the city centre with lots of plants and flowers. It’s won praise from around the UK for its aesthetic qualities, says Roger.

Often a natural SUDS option can be cheaper than the alternative of pipes and storage tanks underground, which in a hilly city like Sheffield may often lead to costly drilling through bedrock.

SUDS that are wet parks or green spaces bring in all kinds of biodiversity too, including butterflies, birds, dragonflies, and native water plants like reeds that help clean the water.

A small pond near Pipworth recreation ground is a four year old SUDS where locals see ducks and wild flowers when they walk their dogs. Nearby, there’s a large grassy depression in the ground, which is actually a 6,000 cubic metres surface water storage facility that will help reduce flooding in the lower Don Valley.

The two are linked by drainage channels: in heavy rain the pond grows (and plastic bottles that drifted down in the heavy rainfall of a few months ago can still be seen a few metres from the current pond edges) and in very heavy and continuous rain, the linked grass bowl will become a temporary lake, and reduce flooding downstream.

Hopefully, the recreation ground won’t turn into a lake too often. But these days, water engineers have to plan for extreme events. The recent heavy storms resulted in a ’1 in 244 years’ event at Redmires, that is, in theory the colossal amount of rainfall is unlikely to happen again at Redmires for another 244 years.

The government has already asked developers and engineers to build in a 30% extra capacity in SUDS for the increased risk of extreme weather due to climate change, and Sheffield is already raising that capacity to 40%, says Roger.

And on Manor Fields Park, a new pond is being landscaped now, to provide extra SUDS capacity. It will be planted up over this year and will become an ‘ephemeral pond’ says Ted Talbot of park managers Green Estate, meaning a pond that will grow to a small lake or shrink to a wet wildlife area depending on rainfall.

He’s now inviting the Sheffield public to come up with a name for the pond, by posting ideas on the Green East social media. Deep Pits Pond and Queen Mary’s Marsh have already been floated, so to speak, but all reasonable ideas welcome, says Ted.