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DELTARES, FEBRUARY 2016
13
B
risbane, January 2011:
the two reservoirs in the
largest river in South-East
Queensland, Australia, can
no longer accommodate
the rain that has fallen. A series of
floods batter the capital and ninety
other cities in Queensland. The result:
35 dead and damage amounting to
between 3.5 and 4.5 billion Australian
dollars. ‘And,' predicts risk researcher
Ferdinand Diermanse, 'it could happen
again tomorrow.’.’
Critical population
Although it was very tempting to
take action immediately, the state of
Queensland decided to draw up a sound
plan first. How probable is extreme
weather of this kind? How high will the
water be, and where? Where we can
build, and where not? ‘A thoroughly
researched and costed plan can not only
save a lot of money, it can also reassure
a critical population that wants the
authorities to consider all the options.’
At the request of the Queensland
authorities, Ferdinand Diermanse
ran the calculations for a range of
scenarios, looking at 309 kilometres
of river in an area abounding in
farmland and urban regions. The work
involved taking all possible variations
in natural processes into account, as
in more traditional approaches. ‘The
di£erence between a lot of rain and
too much rain, for example, is highly
dependent on the wind direction,
where the rain falls exactly, and rainfall
in the previous days. That makes risk
assessment particularly complex.’
Skype
A unique feature of this research is
the close partnership with Australian
experts. ‘Quite oen, a job comes in
and you make a report. In this case,
we delivered all our calculations to
the Australians as open-source data,
together with the models. If they
decide, for example, to build a third
reservoir, they can make adjustments
to the model and see how the level of
risk is a£ected.’
In addition, independent experts
evaluated all the results and Ferdinand
Diermanse explained the numbers
in person during local meetings with
the press and residents of Brisbane.
‘I regularly spent nights sitting at our
kitchen table to attend meetings on
Skype.’
Saving money
The calculations for the Brisbane
River in Queensland were done in Del
FEWS, flood warning soware that is
also used by the Environment Agency
(UK), the National Weather Service
(US) and the Bureau of Meteorology
(Australia). The modular system can be
easily tailored to local conditions and
requirements.
‘It's an investment. But you can use the
system to decide whether to intervene
and where you won't be doing any
building at all. That can produce
enormous savings in the long term.'
Aer the floods of 2011, the authorities of Queensland in Australia need
measures that have been thoroughly researched. People had to be sure the
right steps will be taken. Ferdinand Diermanse of Deltares did the calculations.
BY PJOTR VAN LENTEREN
FLOOD-SENSITIVE BRISBANE
MAPS OUT THE FUTURE
PHOTO: HOLLANDSE HOOGTE
CASE
STUDY