As our population grows our demand for natural resources increases, which in turn puts enormous pressure on our land and our natural soils. Soils act as a natural sponge and can attenuate rainfall at the source. Heavy and storm event rainfall can wash away this valuable resource, and in turn depleting nutrients and growing medium. To help prevent soil erosion, areas of unvegetated soil can be sown with grass or wildflower seed. This can help to prevent erosion and slow down surface water runoff in times of heavy rainfall.

There are several ways in which landscape can help alleviate local flood risk. The planting of trees with large canopies can help slow the rate of rainfall reaching the ground. The force of raindrops hitting the ground is greatly minimised by canopy cover, allowing water to be absorbed into the ground at a more steady rate, with the leaves of the tree also providing some attenuation capacity. The tree itself can also absorb water, with rates varying depending upon weather conditions, evapotranspiration rates, and even species.

Creating rain gardens such as those in Grangetown, Cardiff, helps to reduce pressure on existing drainage systems. The use of trees and plants that are tolerant of wetter conditions can help to slow the rate of rainfall reaching the surface, with only the overflow being released into the wider attenuation system. This method also has the added benefit of increasing the biodiversity of the area and beautifying streetscapes, creating a more idyllic neighbourhood for people to enjoy.


Grangetown rain garden


Permeable hard surfacing across a development can be utilised to provide surface water attenuation, and are often used as part of a site-wide sustainable drainage system (SuDS). It is important to maintain areas of permeable hard surfacing to ensure that they continue to offer that measured functionality. Regular weed removal and de-silting operations are required to ensure that the system efficiently functions.

Blocks of apartments within developments are often required to provide amenity spaces. The design of roofs can be modified to provide amenity space, attenuate water and provide biodiversity for wildlife. This helps to ensure the efficient use of space and can negate the requirement for swales and attenuation basins.

At home, rain gardens can be created at a low point in a garden using plants that are tolerant of wetter conditions, or if there is space a tree can be planted to help attenuate rainfall and absorb more groundwater. Installing a green roof on a garden shed will not only help to improve biodiversity in your garden but will also help to attenuate rainwater. Any excess can be channelled into the rain garden.

ACD Environmental is proud to work alongside multi-disciplinary design teams, to offer bespoke solutions that can help address flood risk on development sites. For more information please contact us.


Rain garden