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Detailed Design 9.4 Critical levels ■ ■ Areas contributing to a storage Detailed Design
Levels are important in any drainage system
component should not be situated below
and especially so for surface based SuDS.
the top level of storage as they may flood
The proposed surface levels should align with
prior to the storage being filled.
the modified flow route analysis in providing
a flow path across the site and storage
For storage components that are sloping,
volumes can be significantly affected by
inaccurate levels.
basins, the ‘effective’ storage should be
determined rather than the entire volume
The following levels should be evaluated such as permeable pavements or linear
when developing or reviewing a design: of the structure.
■ The flow control invert level relative to ■ A review of site levels should not identify
storage - the flow control should not be any obvious obstructions along
situated above the base level of the exceedance flow paths.
storage component unless there is a
Note :
requirement for permanent or semi-
permanent water. The LLFA will carry out a high-level review
of levels only - Liability for design is
■ The overflow level should demonstrate
retained by the designer in all cases.
that the required volume of storage is
contained between the flow control invert
level and the overflow level. Grey to Green project, Sheffield.
75 The 3 flow control criteria: low flow, overflow 76
Facing: Accurate levels were critical at Bewdley and exceedance are demonstrated
School Science Block. elegantly here.
Newham Council SuDS D & E Guide © 2020 McCloy Consulting & Robert Bray Associates Newham Council SuDS D & E Guide © 2020 McCloy Consulting & Robert Bray Associates
