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SuDS Myth Buster Series
03 Aug 2021 12:55     A+ | a-
We’ve gathered together some of the most common misconceptions about Sustainable Drainage Systems (SuDS) that were included in Chris Griffith’s webinar on SuDS myths (hosted by our very own Bill Blackledge, for the Landscape Institute – The full recording is now available on LI Campus).

Chris Griffiths and Bill Blackledge

Image credits are to Chris and Marshalls, who have undertaken some excellent research in this field, providing useful proof that some common SuDS myths are nonsense.

1. Permeable Paving...NO it DOESN'T Clog!

Permeable paving experiment

A layer of soil and dust WILL build up, BUT it doesn’t prevent infiltration, only slows it down. The rate of infiltration reduces by about 10% of the initial rate, and then plateaus. Due to the initial very high infiltration rates, the reduction doesn’t result in a point of failure. The systems are still more than capable of dealing with the maximum UK rainfall.

The worst performing, 19-year-old, paving in Chris Griffiths' test absorbed water at a rate of 223mm/h. The Met Office's heaviest recorded rainfall is 92mm/h.

Read Chris' research in detail here:

2.  Ponds/Basins...NO they are NOT death traps!

Chris Griffiths researched back 20 years, but couldn't find a single death in an attenuation basin. Even the Royal Society for the Prevention of Accidents (RoSPA) agrees that they are safe if well designed (low gradients, no fences).

3.  Permeable Paving...YES it DOES clean water!

Permeable Paving...YES it DOES clean water!

University of Coventry undertook extensive tests, simulating different pollutants and rainfall events.

Out of 300 tests, only 3 samples of water filtered through permeable paving wouldn't have passed World Health Organisation drinking water standards.

4 - Rain Gardens...NO they DON'T generate litter!

Rain Gardens...NO they DON'T generate litter!

Good design and attractive places encourage pride in the environment and discourage litter.

If there is litter near rain gardens, it's likely less than there would have been - and easier to clear because it collects in the low point!

5. Permeable Paving...YES it DOES take heavy loads!

Permeable Paving...YES it DOES take heavy loads!

The sub-base just needs to be designed appropriately, using both structural and hydraulic calculations to ensure both loading and water volumes are accommodated.

There's a British Standard 7533, which Marshalls have elaborated upon with additional categories to ensure 'horses for courses'.

6. SuDS...YES they DO provide Return on Investment!

SuDS...YES they DO provide Return on Investment!

Chris noted that a recent study has found properties increased in value £7.5k for being able to see water from the window.

A retrofit pilot project, on a school in Salford, got their money back within 3 years by not having to pay discharge rates; on top of all the other benefits that come from having SuDS.

5 pillars of SuDS

Check out our post on how one project could have saved over £100k by using SuDS at: (2019, but still as relevant as ever!)
We first ran the blog above as a series of posts on social media channels – follow us to be the first to get updates in future!
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