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hould we stop building in some places, or should

we actually be building dikes? Or is it better to

set aside flood-prone areas for agriculture and

fishing? The unpredictability of climate change

makes it difficult to predict the best approach to

infrastructure for the long term, particularly if an

area under threat is economically important.

Ad Jeuken, a climate adaptation expert, believes that this

requires greater flexibility in decision-making about local and

regional water management. ‘We should be concentrating

less on getting everything arranged for generations to come,

and more on taking different scenarios and the interactions

between them into account. That includes demographic and

socio-economic scenarios.’

Agencies managing water systems have to

take decisions about infrastructure that will be

in place for fifty or a hundred years. How do you

go about achieving that?

‘To start with, you try and decide what you want to achieve

during that time and which developments can undermine

your objectives. Then you select a range of possible climate

scenarios. You try to combine those as well as possible

with the data that you already have about floods and water

shortages. For example, let’s say that heavy rain now results

in flooding once every twenty years. You combine that with

data from the climate scenarios and you may find that the

flood frequency for 2050, for example, increases to between

once every ten years and once every five years. That means

you need to take action.’

Doesn’t that just mean building or raising


‘That is very much the question. You also have to keep

demographic and economic developments in mind. A flood

frequency of once every five years may be acceptable in

sparsely-populated agricultural areas. In that case, a warning

system and damage repair may be enough. However, a lot of

urban development is actually located in flood-prone deltas

because it is there that the trade centres have traditionally

been located. The trick is to strike exactly the right balance.’

Different climate scenarios often produce

a picture that isn’t clear or straightforward.

That makes adaptation even more difficult.

‘What matters is to develop a strategy for the long term that

is flexible enough to respond to unexpected developments.

The traditional planning approach comes up short because

you don’t know what you need to keep in mind. So that

requires what we call an adaptive planning approach. That

factors in not only different futures but also the different

pathways leading to those futures. On the basis of the

present scenarios for precipitation patterns, the first step

will be, for example, to try to raise the discharge capacity

of a river by creating overflow areas. If the river discharge

increases more than expected, you can always decide to

strengthen the dikes later. But you can also ensure that

specific urban areas under threat are protected from flooding,

depending on economic and spatial developments. The trick

is to enhance your administrative and policy flexibility so

that you can respond to change without pushing up costs,

and also without taking more risks.’

It’s a long-term business. How do you get the

public and politicians on board? You can’t

maintain a permanent sense of urgency.

‘That’s right. That’s why it’s important to combine flood

risk management with other objectives. Jakarta is a case

in point. As a result of land subsidence – and not even an

actual increase in the sea level – the flood risk there has risen



Increased flood risks and longer dry periods require changes in infrastructure.

‘But climate change is so unpredictable that administrative flexibility is

really stretched’, says climate adaptation expert Ad Jeuken.