London scoping - ukcip

Final Report
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requirement for future flood protection. Once major new infrastructure is constructed, then
there is a large new asset base which needs to be protected and this in some senses limits (or
renders less attractive) other options, such as using land for green areas which can serve a role
in flood water storage. The issue is, in part, one of how long a time scale is adopted in
analysing urban development and regeneration plans. If one were to adopt a timeframe of 15-20
years ahead (as used in traditional planning), then flood risk would probably not feature as an
impediment to riverside development. Over a 50-100 year timeframe, the evaluation process
would have to change because of the need to take account of the change in level of flood
protection provided by the Thames tidal defences beyond 2030 (hence requiring use of a
scenario planning approach).
An even longer timeframe, i.e. beyond 2100, would require yet another assessment, because of
the accumulated effects of sea-level rise. Depending upon global greenhouse gas emissions and
the uncertain response of the oceans and ice-caps, etc., sea-level rise over the next several
hundred years could challenge the technical capacity to provide adequate levels of flood
protection in parts of London. No thorough assessments of the risks of sea-level rise and
extreme rainfall affecting the river level on these longer time-scales have yet been conducted.
Another issue for the Thames is the potential need to store large amounts of water up and downstream
of the Barrier depending on whether the issue is increased rainfall (up-stream) or higher
sea-levels plus surge events (down-stream), or perhaps both. Re-channelling water out of the
Thames upstream, and into other waterways is one option for coping with large amounts of
accumulating river water. Down-stream water storage is required when the barrier is closed
and this could, potentially, have an adverse impact upon fisheries and cockle beds, which are
protected by EU legislation. Using the river and estuary for water storage purposes to avert
flood risk could, therefore, collide with its natural ecosystem role and functions (Naylor,
pers.com. 2002).
Several of the Strategic Zones of Change which have been identified within the Thames
Gateway for London have included nature reserves, country parks and visitor centres, e.g.
Havering Riverside and Rainham Marshes (a 1,400 ha reserve is proposed, with capacity for a
quarter of a million visitors per year) (MCA 2001). There is clearly a good opportunity here for
such set-aside land for biodiversity to double-up as land for flood water storage. The future of
Rainham Marshes as London’s biodiversity ‘jewel in the crown’, and one of the few remaining
remnants of the marshes that once fringed the River Thames, now seems more certain, with the
London Borough of Havering agreeing that the marshes should be protected (FoE 2002). In
1998, considerable concerns had been expressed when English Partnerships applied to Havering
to build on 50 hectares of the area (FoE 1998). Interestingly, the lack of proper management of
the site in the past had led the opinion to be expressed at that time that the Marshes were ‘not
worth protecting’.
The 142,000 new houses and 255,000 new jobs planned for the Thames Gateway (TGLP 2001)
have huge knock-on implications for the provision of water resource and suitable sewerage
treatment facilities, as identified by stakeholders in the course of the study. The design of the
sewerage system clearly needs to avoid the prospect of overflow at times of high rainfall
directly into the Thames. This high level of development also implies a quite massive urban
development, which could increase water run-off. Potential solutions to this are greater use of
sustainable drainage systems, permeable ‘soakaways’, and so on, though such methods are far
from having been fully proven in a range of situations.