Why landscape architects are the future for sustainable urban drainage

Landscape architects hold the keys to sustainable urban drainage of the future.

For decades we have been putting pipes under the ground, topping them with impermeable surfaces and encouraging water to run off as fast as it falls from the sky.

In our quest to build new homes we have cut down trees and given little consideration to how deforestation impacts on our environment, causing issues like flooding.

In Wales, all new developments are required to include Sustainable Drainage Systems (SuDS) features that comply with national standards. This means that they need to reduce the risk of surface water flooding while creating opportunities for improved water quality and bio-diverse rich habitats.

SuDS, which replicate nature and manage rainfall close to where it falls, can be designed to move surface water, slow it down and provide water storage areas to encourage water to soak into the ground and dissipate slowly into the surrounding river network.

In Wales, construction work cannot start unless the drainage system for the work has been approved.

This is the future for building projects – and landscape architects are leading the way.

It’s all about creating an integrated and holistic outdoor environment that slows water down, enhances bio-diversity and provides spaces for physical and mental well-being.

When we are brought into a new development scheme we work with the natural landscape and look at ways we can naturally enhance drainage.

For us, it isn’t about putting more pipes into the ground or increasing the amount of impermeable hard surfacing.

Instead we take a natural drainage approach that has been around for centuries and make it fit for the 21st Century. We do this by using plants, the soil and sub-soil to help store water when it lands. The water can then be released slowly.

Instead of half an hour’s rainfall hitting hard ground and rushing off a road surface into a gully and straight into the water course or drainage network at speed – effectively creating flooding – we slow it all down.

We are working on a range of schemes from residential developments to visitor attractions where we have used sustainable urban drainage techniques in the new gardens, the public spaces and the car parks.

Water is encouraged to run off from the car park into planted beds which are full of plants that love damp conditions. From the beds there are outlets where water can drain slowly into the wider drainage network containing swales and retention basins.

We are using the same principles at a new natural burial ground we have designed the landscape for. We specified that the hard surfacing is permeable so water is allowed to run into a series of swales – shallow, broad and vegetated channels designed to store runoff and remove pollutants.

These swales are conveyance structures which naturally slow the runoff to the next stage where soil and groundwater conditions allow. From the swales we are recommending a filtration bed downstream and, from there, the water either filters into the ground or gets released very slowly into the drainage network.

It works. And there are huge amounts of benefits – less flooding, it’s better for the environment and biodiversity, it is more cost effective and far less complex and easier to maintain than installing networks of pipes with their high carbon footprint.

And we’re not the only ones doing it.

The National Trust recently bought a tract of land in the lake District where they are considering natural management methods to slow the River Derwent’s flow to reduce the risk of downstream flooding in places such as Keswick and Cockermouth.

Research has shown that reforesting just 5% of the upland landscape in the Lake District could reduce flood peaks by up to 30%.

The principles of rewilding - the large-scale restoration of ecosystems where nature can take care of itself - are also growing in popularity.

When I started my career, landscape architects were perceived as the people brought in to add some planting around the architects design. Because of climate change, people’s awareness of the outdoors and the environment has shifted and our role has become more important than ever in building projects.

Building for the future needs to be landscape driven – it’s what we should have been doing for years.

·         In response to this change, Land Studio is looking for a forward thinking civil engineer to join its growing team and forge new ideas and approaches for the integration of drainage solutions into the built environment.