Page 131 - Updated SuDS Design & Evaluation Guide-Newham V3 Spreads

Detailed Design Green & blue roofs 2. Most green and blue roof substrates have Raingardens Key aspects of raingarden design include: Detailed Design

Recent examples in the UK have focused on a
The raingarden concept was pioneered in
a water storage capacity of between
shallow depth of growing medium with a
Prince George’s County, Maryland, USA in
1. gentle side slopes with water collected at
30-40% void ratio.
1990 when small stormwater basins were
Sedum (fleshy leaved, drought tolerant plant)
the surface
based vegetation. This approach is driven by
proposed for individual houses to replace
3. A simple orifice control together with
2. a free-draining soil, sometimes with an
overflow arrangements provides an ideal
larger regional stormwater ponds.
cost and the idea of minimum maintenance.
underdrain to avoid permanent wetness
opportunity to retain water on the roof
There are now many examples of failure of
3. a minimum of 450mm improved topsoil
Raingardens are designed to collect and
meaning that it does not have to be
planting on this type of green roof due to
with up to 20% course compost
lack of drought resillience.
arrangement is particularly important for
and low risk drives and pathways, has been
urban redevelopment where the building
submersion and wet soil – this includes
1. A minimum 100mm soil depth is stored again at or below ground level.This manage reasonably clean water from roofs 4. garden plants that can tolerate occasional
used where community or private care is
recommended for drought resilience and footprint may take up all of the site. This available to maintain these potentially most garden plants other than those
this design is particularly suitable for a would be referred to as a blue roof. attractive site features. particularly adapted to dry conditions
natural dry grassland vegetation. 5. an overflow in case of heavy rain or
impeded drainage.

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Newham Council SuDS D & E Guide © 2020 McCloy Consulting & Robert Bray Associates Newham Council SuDS D & E Guide © 2020 McCloy Consulting & Robert Bray Associates