flood warnings seem to be a regular feature
of our winter weather forecasts. Weve
become accustomed to the sight of towns and
cities under water, of householders
despair, submerged cars, and the messy aftermath
of mud, gravel, sodden furniture and ruined
carpets. University researchers have been
finding out whats to blame.
where to lay the blame is not always clear:
is it inadequate flood defences, climate change
or a combination of the two? Or are floods
just natural phenomena, which only seem more
frequent because theyre more consistently
reported in the news? Researchers at Leeds
have been studying the figures and found that
the reasons for this watery misery are not
what they might seem.
its an obvious cause and effect: it
rains more, so it floods more. But the increase
in flooding which is real, not imagined
is not matched by an increase in rainfall.
Professor of physical geography, Stuart Lane
(pictured left) , is heading a major
research project to identify what other factors
are causing the flooding, and what action
needs to be taken to reverse the trend.
An example close to the University shows the
size of the problem. Flooding in York has
increased from between ten per decade at the
turn of the 20th century to nearly 50 between
1991 and 2000. Yet there has been no noticeable
change in rainfall patterns during the last
Professor Lane said: Weve taken
dry summers out of the equation and looked
only at only winter rainfall. Weve looked
at the frequency of extreme rainfall events,
but there is still no major change in the
rainfall patterns since 1900 which can adequately
explain the dramatic increase in floods. Something
other than rainfall is causing the flooding,
something which affects how the water drains
off the land, where it can go and at what
speed. That something is the land
itself, and how that land is managed.
The research project is using Upper Wharfedale
as the case study, to look at land management
in the uplands where the rivers begin their
journey and where the rainfall is high. Changes
in agricultural practices have a knock on
effect many miles downstream, in lower-lying
areas where rivers can do a lot of damage
in large towns and cities.
Blaming land management is not just speculation;
the theory is borne out by the figures. The
numbers of floods in York, for example, increase
sharply first in the 1940s and then in the
1980s, and both of these relate to significant
changes in land use.
the 1980s, the European Union started subsidising
farmers per head of livestock. There was a
massive increase in stock density in the uplands.
Sheep and other livestock trample the ground,
reducing infiltration and increasing the speed
of run off, which has a direct impact on the
amount of water getting into the rivers quickly
following periods of rainfall, and so increases
the likelihood of flooding, said Professor
the increase in floods in the 1940s appears
to be directly linked to the digging of drainage
ditches, or grips, in the peat bogs, which
was started at that time to create more grazing
land. There is also a theory that worsening
erosion is increasing the amount of sediment
added to the river bed, raising the bed level,
clogging up the river channel, and so reducing
the amount of water needed to cause a flood.
But water isnt just a problem; its
also a resource. Many of the rivers also provide
drinking water for local populations and support
complex ecological systems, all of which are
also affected by changes in land use. The
research project in Upper Wharfedale is also
bringing water colour and quality, and environmental
impact into the equation.
Hundreds of pieces of equipment are already
in place in Upper Wharfedale measuring water
level, colour and sediment discharge. Certain
grips have been blocked to analyse the effect
on where the water goes, and how quickly.
Hydrology specialist Dr Joe Holden said: Very
little is currently known about what is happening
in these upland areas, despite their crucial
role in what happens further downstream. Data
collected over the next three years will allow
us to start to fill in the blanks.
data will be used to help develop a model
for assessing the impact of different kinds
of land management, not just on flood prevention,
but on water quality, agriculture and the
ecology of the area. Dr Chris Brookes is helping
to develop the model which, although created
for Upper Wharfedale, can be adapted for any
kind of upland environment, whether forestry,
peat bog or pasture.
effects of climate change are starting to
be felt, but the true impact will take a while
to show up in overall patterns of rainfall
and flooding, said Professor Lane. While
many of the decisions over changes in behaviour
to tackle global warming may be out of our
hands, how we use the land around us is in
our control. Our model will enable people
to have an effect at a local level, rather
than waiting for others far removed to make
those decisions for them.