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DELTARES, FEBRUARY 2015
9
DOSSIER
Land subsidence
in peat areas
Land subsidence in peat areas in the Netherlands damages
housing and infrastructure. In other countries where peat
areas are located on the coast, these areas are increasingly
being submerged due to land subsidence, with all the
inevitable harmful consequences. Despite the high costs
of land subsidence in peat areas worldwide, this is still an
under-appreciated problem. A lack of familiarity with the
phenomenon is getting in the way of adequate counter-
measures. Raising awareness of the true cause of the damage
is the first step on the way to an answer. In technical terms,
there is no ‘one-size-fits-all’ solution. On all occasions, tailored
approaches are needed, and a willingness to invest in the future
of an area is essential. That is because counter-measures are
not cheap, and they produce results in the longer term only.
We need to develop them, and make them into
attractive alternatives to living on Java. All these
solutions cost time.’
As we talk, the rainy season in
Indonesia has just begun. Are you
prepared?
‘The main rivers have been dredged and we
have strengthened dikes. We have also been
collaborating with organisations including
Deltares and the Indonesian meteorological
service on the development of a warning system.
It is still not perfect, but people are now informed
by their district head when there is a flood risk in
their area.’
But is that enough to get through the
rainy season unscathed?
‘Work has not yet been completed on all the
river dikes because we are still negotiating land
purchases. Even so, flooding will not be as bad
as in previous years.’
Another problem is land subsidence,
which may allow sea water to flood
Jakarta. What are you doing there?
‘We are gradually tapering off the pumping up
of groundwater. New complexes are no longer
being given permission to use groundwater.
We are also trying to supply people with clean
water in different ways by treating river water.
And we will be injecting water into the ground
to replenish groundwater. A group of scientists
in Bandung is working with Deltares on the
development of a model to map out and stop
land subsidence.’
There are also plans for the construction
of a dam in the shape of an eagle offshore
Jakarta: the Great Garuda. Will that still
be needed if you manage to stop land
subsidence?
‘On the one hand, we are continuing to work on
the plans for the Great Garuda, but we are trying
to stop land subsidence at the same time. If we
are successful, construction of the Great Garuda
can go ahead, but there will be an open link to
the sea, preventing the potential accumulation of
river debris behind the dam.’
Indonesia asked the Netherlands for
assistance a few years ago. A consortium
of Dutch companies is now helping. Does
Indonesia not have the know-how itself?
‘We can learn a lot from the Dutch. Working
together with themmeans we don’t have to
start from scratch. With our coastal defences,
we were able to map out the problems quickly
using models and data, and so we were able to
establish a clear picture for everyone. We use
the Deltares open-source software for the flood
warning system, and that allows us to predict
water flows in rivers using simulations.’
Can the Netherlands learn something
from Indonesia?
‘We have teamed up on the development
and upgrading of a programme for river
management. Technology developed here can
also be used elsewhere in the world. Indonesia
has become the water world’s testing ground and
laboratory.’
‘Working together
with Deltares
means we don’t
have to start from
scratch.’
An impression of the Great Garuda offshore Jakarta
IMAGE: NCICD