The Mayor's draft water strategy - london.gov.uk - Greater London ...

62 The Mayor’s draft water strategy
gardens was a permitted development right,
and therefore could generally be carried
out without planning permission. Following
consultations in 2007, the government
accepted that, given the contribution of hard
standing to surface water flood risk, it would
restrict householders’ to porous surfaces.
Planning permission is now required for
impermeable surfaces in front gardens larger
than five square meters 63 .
4.12 The Draft Flood and Water Management
Bill will require developers to include
sustainable drainage, where practicable, in
new developments, built to standards that
reduce flood damage and improve water
quality 64 . It will also amend section 106 of
the Water Industry Act 1991 to make the
right to connect surface water run-off to
public sewers conditional on meeting the
new standards. It will give responsibility
for approving sustainable drainage systems
in new development, and adopting and
maintaining them where they affect more
than one property, to a SUDS approving
body, generally local authorities. The Mayor
supports the legislative changes proposed in
the Draft Flood and Water Management Bill
in respect of surface water management.
Proposal 8 The Mayor will encourage green
roofs rainwater harvesting, grey water
recycling and sustainable drainage through
planning policies in his new London Plan.
4.13 There are instances where surface water
drains have been connected to a foul sewer,
when connections to separate surface water
drains or watercourses were available and
would have been more appropriate. This is
discussed more fully in paragraphs 5.17 to
5.21. The proposed changes in the right
to connect to a public sewer will require
effective enforcement by Local Authorities.
Risks of flooding
4.14 In London, tidal and fluvial flooding presents
a significant risk. About 400,000 properties
are at risk from tidal flooding while about
100,000 properties are at risk from fluvial
flooding. Also at risk are the Underground
system, power supplies, telecommunications
and much other critical infrastructure. The
Thames Barrier and associated defences
protect those properties at risk of tidal
flooding to a very high standard so that
there is less than a 0.1 per cent chance
of flooding in any one year. Those at risk
from fluvial flooding are protected to only
a moderate standard, typically there is
between a one and five per cent chance
of flooding in any one year. The flood risk
from tidal flooding is therefore very low in
probability, but very high in consequence
and for fluvial flooding there is a moderate
to high probability, but with lower
consequences.
4.15 Flooding can have a significant effect on
people’s health and wellbeing. As well as
physical problems, such as colds and chest
infections, flooding can cause increased
levels of stress and anxiety, for example,
as a result of having to live in temporary
accommodation, paying for repairs and
dealing with insurers 65 .