Supplementary memorandum submitted by
the Flood Hazard Research Centre, Middlesex University (FL 113a)
Is it easier to justify flood defence protection
for well-off households and urban areas than poor or rural areas?
Decisions about flood risk management measures
(including flood defence) are guided by a benefit cost analysis.
Such analyses have also dominated the Priority Score system that
Defra has had in place to "sieve" out those schemes
that are to be funded. There is evidence that, within the "block
grant" system of funding to the Environment Agency from Defra,
the Agency's funding decisions remain dominated by the benefit
costs tests.
WELL-OFF
HOUSEHOLDS RATHER
THAN POOR
HOUSEHOLDS
The benefits of flood defence are the flood
losses thereby avoided. The higher these potential losses, the
more worthwhile will be investment to reduce these losses.
Thus, for one residential property defended,
it will be worthwhile to spend more on flood defence if that property
is large and full of valuable contents. In these circumstances
it will indeed be "easier to justify flood defence protection
for well-off households'.
But flood defence projects traditionally do
not protect just one property; indeed there are substantial economies
of scale in flood defence works such as embankments, so that most
(if not all) state funded flood defence projects protect land
on which a number of properties are built. And the larger the
area of land (other things being equal) the more cost-effective
will be most flood defence schemes (because cost is related, very
approximately, to the length of the perimeter of the area affected).
Poor households tend to live in small houses
packed closely together. Thus for any given area protected (and
any given length of perimeter embanked) there will be more poor
households protected.
Taking examples from the Thames catchment, in
affluent Maidenhead there might be just five households per hectare
of land protected, living in large detached houses, whereas in
one hectare on the Osney Island area of Oxford there might be
100 households occupying small terraced dwellings. The potential
flood damage to one house in Maidenhead is not 20 times the flood
damage in a house in Osney Island, so in that case it is not "easier
to justify flood defence protection for well-off households (rather)
than poor ... areas". Indeed, other things being equal,
the reverse is the case.
So, it all depends on the density and type of
each development, rather than just the affluence or poverty of
the households.
URBAN AREAS
OR RURAL
AREAS
By definition, rural areas are less densely
developed than urban areas. Therefore flood defences there are
less easy to justify, in that fewer households and businesses
are likely to be defended per unit area of land or per unit length
of embankment or river works.
But there may be other factors that influence
decisions. Rural flood defences may be cheaper than urban flood
defences. This can be because rural areas can accommodate earth
embankments whereas urban areas may have to have concrete walls,
owing to the lack of space for building the flood defence works.
The one may be cheaper than the other. And land purchase costs
for these works may be lower in rural areas than in urban locations
although, since land purchase involves a transfer between buyer
and seller, there is no economic gain/loss to the nation (which
is what benefit-cost analysis counts).
In general, however, it is easier to justify
flood defence protection for urban areas than for rural areas.
Edmund Penning-Rowsell
Flood Hazard Research Centre
Middlesex University
December 2007
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