Environmental Engineering Reference
In-Depth Information
25
Operational European Flood
Forecasting
Hannah Cloke 1 , Florian Pappenberger 2 , Jutta Thielen 3 and Vera
Thiemig 3
1 Department of Geography, King's College London, UK
2 European Centre for Medium-Range Weather Forecasts, Reading, UK
3 DG Joint Research Centre, Ispra, Italy
forecasts) can significantly contribute to flood prepared-
ness strategies for larger rivers (Golding, 2009; Thielen
et al ., 2009b). A recent study outside Europe indicated
clearly the potential of early warning systems to reduce
the economic impact of floods (Subbiah et al ., 2008).
However, predicting floods with sufficient lead times
to maximize the protective measures that can possibly
be taken, is not an easy task. The hydrological processes
that transform rainfall into river runoff are known to
be highly nonlinear (see Chapter 11) (Anderson and
McDonnell, 2005), and hydrological responses can be
said to be unique to particular catchments (Beven, 2001).
In order to forecast river flooding accurately, a great deal
of spatially and temporally distributed data is required
on future rainfall, catchment characteristics (such as soil
moisture conditions, topography, snow cover, soil per-
meability and depth, land cover type) and the movement
of the floodwave along the river (so-called flood 'routing',
see Chapter 11). The design of the best flood forecasting
system may differ from catchment to catchment, balanc-
ing data resolution, quality and availability with model
representation of atmospheric, surface, subsurface and
channel routing processes that contribute to flooding,
all of which is particularly challenging at larger scales
(Cloke and Hannah, 2011). In addition the requirements
of the end-users of the system who will be making deci-
sions based on the flood forecast must be considered
25.1 The problem: providing early flood
warning at the European scale
Europe has repeatedly encountered devastating floods
in recent years - for example, the historic floods that
affected the Elbe and Danube rivers in 2002 and 2006
and the floods in the UK in 2007. Many of the major
rivers in Europe cross national boundaries and transna-
tional fluvial floods are considered to be more severe
than non-shared rivers in terms of their magnitude, area
affected, death toll and financial damage (Bakker, 2007).
Widespread flood events, such as the May/June floods of
2010, which seriously affected more than five countries at
the same time, need coordinated preparedness and crisis
response not only on different levels within the country
but also on an international scale. Flood forecasting is one
of the most important mechanisms for flood prepared-
ness and reducing the damaging effects of flood events,
especially for larger rivers (Thielen et al ., 2011). With suf-
ficient warning a range of measures can be taken in order
to mitigate the effects of flooding (Penning-Rowsell et al .,
2000; de Roo et al ., 2003). These include operating river-
control structures, erecting temporary flood defences
such as demountable barriers as well as public warnings
and evacuations. In particular, forecasts of possible flood
events 2 to 15 days ahead (known as 'medium-range'
.
 
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