Page 140 - Bexley SuDS DESIGN & EVALUATION

Detailed Design The safety considerations in basin, wetland 3. Permanent pond depth need not exceed
600mm as this is a common depth of
and pond design should be considered
natural ponds and where most biological
carefully.
activity occurs. However, a depth 600mm
1. The profile of the structure should allow
without regular maintenance means that
easy and safe access for people and
vegetation will cover the pond in time.
maintenance machinery. Slopes should
Most wetland edge plants cannot colonise
not exceed 1 in 3 or 1 in 4 and in larger
beyond 1.2m depth of permanent water.
basins access ramps with a more gentle
slope should be considered. The idea of a
the pond, with surrounding shallower
series of slopes and level benches is now Therefore, an deeper area in the centre of
benches can be considered if open water
accepted as an appropriate detailing for
is desired. Effective storage of 600mm
SuDS basins and ponds.
over permanent water depth of 1.2m
2. The overall depth of temporary storage provides a total potential stored depth of
should not normally exceed 600mm as 1.8m and the design must take this into
this depth is critical for a feeling of safety account.
in water. The bottom of the temporary
storage dry basin should slope gently so
that most of the time the base is firm and
dry. Shallow micropools and wetland
habitat should be integrated carefully into
the basin as they will not be visible when
135 the basin is full of water.

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London Borough of Bexley SuDS D & E Guide © 2018 McCloy Consulting & Robert Bray Associates