Geography Reference
In-Depth Information
compares the costs of such works with the benefits
that they generate (Penning-Rowsell
et al
. 1994).
The issue at stake here is whether a major
scheme can be justified given the relative poverty
of the population in this somewhat deprived area
of northern Britain and the fact that such cost-
benefit analysis favours protecting richer people
and more valuable property since their more
valuable assets at risk from flooding generate
higher calculated benefits against which to
compare costs.
Table 7.2 gives the results from this survey,
and these are not untypical of similar
calculations in other major urban areas. Up to
4823 properties could be damaged by a flood
with a return period of 250 years, and up to
1000 properties could be affected by the fifty-
year event. Damage to these properties would
be £94.5 million and £13.6 million,
respectively. The majority of damage in the 250-
year event here would be suffered by
householders (48 per cent) rather than the
industrial concerns (11 per cent). For the fifty-
year flood, 73 per cent of the damage would be
residential, since most of the industry is located
at the upper margins of the floodplain.
insurance is often not taken up by those with
lower than average incomes. A flood warning
system is already in place, and the additional
solutions proposed are limited to engineering
schemes. However, these can be implemented at
different standards and costs:
Scheme A:
Two flood storage basins in the
floodplain, plus river channel works
designed to give protection to 3269
properties against the 100-year event,
costing £11.3 million.
Scheme B:
A single flood storage basin and the
same river channel works, protecting
approximately 2000 properties against
the 74-year event and costing £7.1
million.
Scheme C:
Just the works to contain flood waters
within a dredged and thereby enlarged
channel, giving only a 1 in 39-year
standard of protection, to only about
800 properties, but at a cost of only
£2.9 million.
Which gives better value for money? As part of
government moves in Britain to control public
expenditure, which in turn are a part of moves to
rein back the role of the state, these schemes are
subject to rigorous economic appraisal.
Application of the decisions rules developed by
the British government in association with
Middlesex University (MAFF 1998) gives the
results inTable 7.3.
Engineering options and standards
By any standards, this is a serious flood problem,
with over 4000 houses and probably 12,000
people at risk. Many would not be insured, since
Table 7.2
The potential flood damage to different land uses in the River
Irwell floodplain.
