Page 38 - Newham SuDS DESIGN & EVALUATION GUIDE

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Concept Design 7.4.4 Source Control - managing runoff at source 7.4.5 Conveyance of runoff between SuDS components Concept Design

Where runoff is conveyed below ground
Source Control features include pervious
Runoff should travel along the management
Source control also ensures that SuDS
train at or near the surface wherever
surfaces, filter strips, green / blue roofs, and
through a pipe, for example connecting one
components are less susceptible to erosion
further down the management train, as
SuDS component to the next to facilitate
some basins and swales. Source control
possible. The features commonly used for
crossing under a road or pathway, the invert
this purpose are swales or other vegetated
runoff is not conveyed at peak flow rates
features slow the flow of runoff, and remove
the worst pollution at the beginning of the
along the system, thereby increasing the
channels and hard-surfaced channels such as
level of the pipe should be kept as shallow as
management train.
potential for interception losses.
possible to re-connect flow into surface SuDS
rills, gutters or dished channels in a more
Source control features protect the remaining
short connectors, without inspection
through permeable pavement sub-base as
parts of the management train, enhancing
well as filter drains and under-drained swales.
chambers or bends, to reduce the risk of
amenity and biodiversity within the urban context. Conveyance is also possible features. Pipes should ideally only be used as
blockage and allow simple rodding or jetting
development. Surface conveyance can provide the when necessary.
following benefits:
The CIRIA SuDS manual (Page 876) notes
■ a reduction in infrastructure costs
that:
■ increased interception losses
■ treatment of pollution
“SuDS design usually avoids use of below-
■ ease of maintenance ground structures such as gully pots, oil
interceptors, and other sumps which are a
Design Note: ■ easily understood SuDS – legibility
Source Control features, such as pervious pavements and blue-green roofs, can be designed wildlife hazard, often ineffective and
to attenuate all of the 1 in 100 + CCA storage, with the introduction of a simple flow control ■ connectivity for wildlife expensive to maintain.”
33 device. ■ attractive landscape features. 34
Identification of surface or shallow sub-
A basin without source control can result in silt,
oil and litter pollution that reduces both the surface conveyance at the Concept Design
amenity and biodiversity value of the feature. stage is important to ensure that these
pathways are retained through the remaining
design process.

Conveyance swale at
Waseley Hills High
School, Worcestershire.

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