SuDS: the solution to our urban flooding problem?

14th January 2025

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Contents

What are SuDS?
Why choose SuDS?
Rain gardens
Benefits of rain gardens

It is hard to ignore the signs. Extreme weather events are becoming more frequent and are having a greater impact on our lives. Storms Dudley, Eunice and Franklin in February 2022 caused devastation to communities across the UK. As a result of the extreme weather conditions, London was issued with a rare ‘Red Weather Warning’ by the Met office, and people were told to prepare for potential flooding[1].

As increasing numbers of people move to urban areas combined with the widespread use of impermeable surfaces such as concrete for pavements, driveways, and roads; as well as a lack of greenery and vegetation, communities are more vulnerable to flooding. Almost a quarter of London constitutes gardens, but this is disappearing under paving slabs, decking and concrete. We are losing gardens at the rate of an area two and a half times the size of Hyde Park every year[2]. This is not sustainable and exacerbates flooding.

[3]

So what can we do to make our towns and cities better protected from flooding? SuDS are one solution.

What are SuDS?

Sustainable drainage systems (SuDS) provide a way of effectively managing the drainage of surface water. The aim of SuDS is to manage water as close as possible to where it falls. They offer a way to manage rainwater that mimics natural drainage in nature[4]. In urban areas, hard impermeable surfaces such as concrete, asphalt and stone prevent natural infiltration. SuDS will aim to direct and slow down surface water runoff into underground aquifers to recharge groundwater supplies. Permeable layers including soil and vegetation ensure the water is not captured or redirected to another location.

Why choose SuDS?

SuDS can[5]:

· Manage water quantity

· Improve water quality

· Provide amenity

· Enhance biodiversity

Maintenance costs for SuDS are 20-25% lower than traditional drainage schemes. SuDS can speed up the approval process by helping to meet local planning requirements.

Rain gardens

Rain gardens are a type of SuDS that are small depressions in the ground that can act as infiltration points for roof water and other ‘clean’ surface water. Through the incorporation of native vegetation, rain gardens not only help to reduce the risk of flooding but are also a way of greening our grey towns and cities. This type of SuDS is also a great way of getting communities involved, especially with the planting and maintenance.

Benefits of rain gardens

Low maintenance garden
Can absorb up to 30% more water than grass
Opportunity to create a nature garden incorporating a wide range of plants and trees
Reduces erosion by slowing heavy rainfall
Increased planting attracts insects and birds
Flexible layout to fit into the landscape

Community Rain Gardens - children and adults getting involved with the planting of the rain gardens in Waltham Forest

Other SuDS features include:

Green roofs
Swales
Nature ponds
Wetlands

Our towns and cities need to be better prepared for flooding.

As the size of our urban areas increase, and more people move to these areas, we need to put in solutions that reduce the impact of flooding whilst adding nature and greenery. SuDS are a great solution: they reduce flooding by mimicking natural drainage in nature, add native plant species, improve biodiversity levels, make our streets more attractive and greener the grey. It would be great if we could have more rain gardens and other types of SuDS across London and all towns and cities. Multifunctional in nature, SuDS are certainly a solution to our urban flooding problem.