Mitigating flood risk – Rain water management

PDP_Rain Water Management

In a natural landscape, rain water is naturally absorbed and soaked into the ground, feeding water streams and rivers, supporting trees and vegetation as well as regulating ambient temperature by surface evaporation.

Construction and developments alter the water cycle, changing how, when and more importantly where our rain goes by increasing surface runoff and washing off pollution from our roads and hard surfaces. As the flow of water increases and drainage capacity is compromised, the risk of flooding is also higher. Permeable surfaces help to slow down water flow allowing watercourses to deal with excess water better decreasing the risk of flooding with the added benefit of proving better water quality to our watercourses.

Permeable surface can include:

  • Permeable paving
  • Rain gardens
  • Green roofs
  • Tree pits
  • Swales
  • Bio retention areas
  • Wet basins and Ponds
  • Dry basins
  • Wetlands
  • Underground water storage

Using permeable surfaces allow rainfall to soak into the ground, rills, channels and bio retention areas slow the flow, treat the water and store the rain. Vegetation also increases surface water runoff capture, providing biodiversity and ecology networks.

All of the above can be integrated into any project providing a great opportunity for the creation of great spaces for the community that are resilient and are able to adapt to a changing and challenging climate. A good example of this is the Strutts Centre and their Rain Garden retrofit project in Belper, which has no doubt helped to improve the local environment.

As we come to the spring and summer, if you are a keen gardener like me, you will be used to hearing about hosepipe bans and water restrictions in parts of the UK. A topic perhaps less discussed around here, is water demand in our developed environment. Just to bring an example from across the pond, in the western USA in years of normal rain fall, landscape irrigation can account for up to 43% of all residential water use, and perhaps closer to the UK, up to 26% in the wetter eastern USA.

Perhaps we all, architects, planners, designers, gardeners, citizens in general should open our eyes to a better water management approach from the outset on every project, however small they are and as simple and common as a new driveway.

Fernando Collado Lopez, Architect, Planning & Design

Top Images: With thanks to the Strutts Centre – Brick rain channel and linear rain garden in front of the old caretaker’s house.

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