Sustainable Design
Swales can be incorporated into your design to collect rainwater directly from gutters. Providing a sustainable way to manage runoff and store rainwater as well as helping to prevent flooding and providing a source of water for wildlife.
Sustainable Design
Sustainable swales for water retention
These pictures come from a recent project where I've been working with Nick from www.nslandscapedesign.co.uk who has implemented the design with careful attention.
I re-designed the front garden of this client built eco-house, after they were left with a mix of rubble and stones, soggy compacted clay soil, a swale that had been dug too deeply and a previous planting plan that didn't work for the finished space they'd ended up with, post build.
Something had to be done and they needed a new design to bring it all together.
Form and Function
The new design features a sweeping path that narrows and widens, creating a natural desire line around the swale that directs you in another direction around the house.
A major part of design work is about form and function and utilising a space better. If this was left as lawn it would gradually get worn down as it would be too easy to take short cuts across the garden. This creates a new planned approach where you can move around the front garden with a natural flow.
The gravel path also frames the swale, allowing the planting to take centre stage but keeping it in it's zone. The path is purposefully edged with steel, which keeps the whole area looking sleek and tidy but with the planting being loose and natural.
Sustainable Design
The design has incorporated any of the left over materials from the main build; gravel from the driveway, York Stone from the main patio at the back of the house, and lime-stone boulders and rocks that were found on the site. All of these have been incorporated into design.
The swale itself is a sustainable drainage solution which collects all the rainwater from around the house.
Rain comes down the various gutters, into the drains, which then empty into the swale and is held there until it gradually seeps through the ground. It's a natural way of holding back the water to help prevent flooding but also serves our wildlife by providing a natural source of water and habitat for certain species.
Challenges of the site
• Builders had previously dug out the general swale area but it had been dug out too deeply, keeping it from being able to drain efficiently.
• The soil left on the site had building debris and lots of stones and rubble incorporated into it.
• There was a high clay content which did not aid drainage.
• The soil was also anaerobic where the water had been sitting for a while and not draining away.
• The budget was tight.
Solutions
Take out 100-150mm off the top of the original soil and rotavate what's left.
Raise the base of the swale by adding in shingle or gravel to the bottom, so the level of the bottom aligns with the drainage channels allowing the water to escape more efficiently
Add some larger boulders of limestone, rocks and pebbles these were available around the site but would aid drainage, help against soil erosion and create areas for invertebrates to hibernate in.
Add a porous membrane to the lower sides and bottom of the swale to help keep weeds at bay.
Add Rain Garden soil to the sides and top of the whole area at least 150mm to the top and sides.
Around the top, soil can be mixed in with free-draining top soil
Add plants suitable for a swale. The plants nearer to the bottom and lower sides needed to be moisture loving, or boggy plants. Plants can become more drought tolerant as they move up to the top of the swale.
Planting Palette
Shrubs Cornus sanguinea 'Midwinter Fire' , Euonymus alatus compactus and grasses Calamagrostis, Molinia give structure and colour throughout the year.
Also providing changing leaf colour through autumn to bring beautiful reds and golds at that time of year.
Other grasses are used for groundcover like Acorus ogon and Luzula nivea, these are good for fairly wet soils and evergreen/semi-evergreen, so will work well up the sides of the swale.
Ferns and Iris towards the bottom, where it's going to be fairly wet most of the time.
Perennials are both a mix of moisture and drought tolerant depending on where they sit on the swale. The client already had some Hydrangea's so I had to include those into the design. Otherwise it's blues and whites, Amsonia, Eupatorium, Lythrum salicaria 'Blush', Salvia ulignosa with some flashes of lemons coming from Rudbeckia 'deamii'