To many eyes, plants look too simple to do anything but plants can remove most of our stormwater, lower council spending by 20% and store carbon, and everyone gets more real green-space too. But tradition and fear of the unknown mean few are rushing to do this. Also it is SO easy to dismiss planting designs as just aesthetics and those who design planting schemes as only gardeners – a loss to all of us.
This is where it all comes together – Sustainable Stormwater Systems*
*SuDS goes by lots of names: a word-war which weakens the original idea. SuDS suggests water – and the association is apt and useful. That said, these principles have broader application than just urban systems so I tend to use Sustainable
urban Drainage Stormwater Systems (SSS) to encompass urban stormwater and rural run-off.
Why do something different with stormwater? What’s wrong with pipes?
Water is a very strong solvent and stormwater is too. As rainfall turns into stormwater and then run-off, it dissolves and gradually erodes the surfaces it flows across and carries off loose particles. Some particles attract further particles and the whole flow ends up in a stream and then the sea. Due to our lack of thought this is a wasteful and destructive process that ignores natural cycles – we’re destroying the Earth.
A natural system (forest, grassland, wetland or even a river) conserves nutrients as they are scarce; it puts nutrients ‘in the bank’ all the time through plant uptake and growth. For instance nitrate – N, phosphate – P, and potassium – K are elements essential to plant growth, even water is held tightly.
But our technical society produces many complex chemicals that don’t break down and that accumulate in soils, groundwater, rivers, the sea and in us. We also mine some (e.g. phosphate) and make others (e.g. urea) and then use them wastefully where their levels far exceed natural systems’ ability to handle them (plants, soils, rivers). From this we get algal blooms, blue babies, and unswimmable rivers. With the complex chemicals (synthetics, plastic softeners, compounds with mercury, lead, cadmium, tin…) we experience chronic medical conditions and wildlife population crashes.
Our artificial surfaces shed water faster and in greater quantities than natural sites, with these volumes rising to such levels that no amount of engineering can reduce their impact.
But bad habits have a habit of catching us unawares…
Currently approx. 30% of a city’s spending is stormwater-related. Climate change has resulted in a shift from stable seasonal weather to (for instance) flood events interspersed with droughts. Seasonal rains are a thing of the past for many regions – ask a farmer, ask yourself, ask the Earth, not the MSM.
At the same time we’re living in a new ‘now’ where the fuels that’ve enabled our society are now threatening both society and human life itself. As it takes many decades to introduce a new fuel we need to design systems that either self-maintain or that can be built and maintained manually.
What is SUDS?
The best way of solving stormwater (lowest-investment / real-results ratio) is to look at how forests, grasslands, wetlands and rivers handle storms and see where we can use their solutions to hold on to nutrients, destroy toxic agents and slow-and-reduce water flows … how far can we emulate nature and bring natural processes into the city?
SUDS can be very simple; it’s about doing three things repeatedly:
- Intercept – stop and slow raindrops before they hit the ground
- Detain – hold water so it evaporates (blue colour in image above)
- Retain – keep some to give our plants the fuel they need, and
— let a tiny bit go to the river
… keep repeating from plants up to cities. We aim to create a multiply-redundant network. Redundant? yes, redundancy has been frowned upon but the natural world (and thoughtful engineering) have layers of fail-safes and apparent duplication. Redundancy means no part of the system is over-stressed and when it needs to work hard – in a storm or through a pandemic – it can and does, every time, with less input from us. You can easily see how the stormwater system works and problem-solve, fix and extend as needed – no digging (for buried pipes) required!
SUDS is open-source (like some software). Literally we need to see the water all the way from source – where it falls as rain and snow – to sea where it re-enters the water cycle.
By keeping the water above-ground we maximise water contact with air (and plants) to increase the rate of water loss to air. By doing this from single houses up to the whole town, severe storm run-off doesn’t occur and a piped network becomes unnecessary. This is where the monetary savings kick in big-time; for a single industrial site stormwater system savings of 20% to 50% are reasonable; for a subdivision or city, savings of 15%+ are normal.
Where conventional drainage is impossible this can make worthless land valuable.
Some SUDS – by least to most complex
– Lot parcelling to match with water flow (new developments)
– Rainwater barrels on downpipes, and rain chains
– The right plants … all plants have different abilities to transpire water
– Many small shallow water basins / rain gardens to detain the flow
– Rough surfaces
– Planted gravel drives (and parking lots) to detain and allow water to infiltrate
– Raintanks for car washing and non-drinking use
– Houses on piles not slabs … to protect existing natural water flow
– Porous concrete and asphalt (also provide much quieter roads)
Imagination is the only limit with SUDS
Plants Really Work by Nigel Cowburn April 14, 2020
What goes around comes around by Nigel Cowburn April 21, 2020