Sustainable Urban Drainage Systems [SUDS] is an approach to drainage that recognises the wider consequences of urban development. In built-up areas, rainfall has little or no natural drainage route, and so must rely heavily on drainage infrastructure.

While conventional urban drainage can capture and transport surface water, there is a limit to its capacity. As expansion of residential and commercial areas continues, with extra roads to serve them, the existing drainage network’s margin of ‘spare’ capacity shrinks.

When major storms occur – with sudden and significant downpours of rain – the system may not be able to cope. Localised flooding and damage to property may be the consequences. This situation is clearly not “sustainable”.

Natural drainage
The majority of rain falling on natural, undeveloped land will soak into the ground and slowly infiltrate through to streams, rivers and groundwater. A small proportion of the water that soaks in will be removed by evapotranspiration through plants.

In green field areas, only about 20% of rainfall runs directly off the surface into watercourses.

The need for Sustainable Drainage
When any previously undeveloped site is built on and paved over, the majority of the water quickly runs off the impermeable surfaces into drains and then into nearby streams and rivers.

In developed areas, only about 20% of rainfall infiltrates into the ground and watercourses.

Reducing the risk of flooding and pollution
In times of very heavy rainfall, the concentrated volume and velocity of surface water place excessive pressure on existing watercourses and local drainage infrastructure. There is an increased risk of flooding, both locally within developed areas,
and also downstream.

The sudden heavy volumes of water can also pick up pollutants
from impermeable urban surfaces and carry them into natural watercourses, to the detriment of water quality and the environment.

SUDS is dedicated to reducing and eliminating these risks.

SUDS: 3 principal aims
In summary, the three key aims of SUDS are therefore:

• To limit run-off from developed areas to similar levels
  that were usual pre-development
• To improve the quality of the run-off
• To improve amenity

Two fundamental elements of SUDS systems are:

Attenuation Crates

Permeable Paving

Please contact us for further information.