Geography Reference
In-Depth Information
Box 7.2
House raising as a flood alleviation strategy: an example from Australia
Most attention is given by engineers and governments to
flood alleviation strategies that involve major
construction, but in many cases the individual can make
adjustments to their property and behaviour to minimise
flood damage potential.
The example below shows a case of house raising
in Lismore, NSW, Australia. Many hundreds of the
town's properties have been raised in this way, thus
reducing the direct damage that the frequent flooding
brings. The frequency of this flooding has approximately
doubled in the fast fifty years along this north Australian
coastline, and many of the houses were originally
constructed at ground level during a period of
infrequent flood events.
Research has shown that this house raising is a
rational strategy for the individual house owner, in terms
of the costs of the raising compared with the benefits of
flood damage avoided (Penning-Rowsell and Smith 1987).
The main problem that remains is that the households are
isolated at times of flood, and this can cause distress and
the dislocation of the inhabitants' lives. They will also suffer
poor access to medical and other facilities that may be
needed in the days or weeks that the flood waters
surround the building.
Plate 7.1
House raising against
flooding in Lismore, NSW,
Australia. Both house were
originally at ground level; the far
one was raised 3 m to above
flood levels.
criticism of the former approach focuses on the
environmental damage that such works can bring,
and the way that certain strategies—mainly
levees— can create rising flood losses if they are
overtopped or breached. The structural approach is
generally reactive: a flood hazard has been created
by human occupancy of a flood-affected area and
needs to be tackled at the location of the hazard to
prevent future flood damage, either by major
engineering river works or with more minor
schemes such as protecting individual properties.
The non-structural alternatives are both
reactive —flood relief and flood insurance being
classic examples—and pro-active. The latter is
shown by land-use control measures either
designed to reduce runoff through controlling
flood flows high up in the catchments or by
controlling land use in floodplain areas to deter
'encroachment' there of damageable property and
vulnerable populations. In most circumstances,
what is optimal in terms of damage reduction and
the cost of the mitigation strategy is a combination
of several measures, such as structural flood control
backed up by warning and insurance systems, or
land-use control supported by emergency relief.
