“History can help maintain the memory of risk”

The whole country, on both sides of the shore, is, so to speak, a vast sheet of water.“. “The Vesdre has taken on the appearance of a river, and an angry river“. These quotations do not date from last July. They date respectively from 1878 and 1880. Paul Delforge, historian at the Destree Institute (and also Calidifontaine), found them in the press of the time.

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Following the floods of July 13 and 14, 2021, he undertook to list all the floods that occurred in the Vesdre valley. And, as often, this plunge into the past can help illuminate the future. The historian is convinced of this. He told us how, during this interview.

The first conclusion of your research is that there have always been floods?

Yes, for the Vesdre, we can say that, since the middle of the 19th century, there has been on average one flood per year. There are years when there are 3-4, and others when there are none. But of course, their magnitude can vary. And it is in this, I think, that the historian’s approach is original. We have had rainfall and hydrometric measurements for a few decades, but we don’t have much information on older times. As a result, flood recurrence forecasts (‘it’s a flood like there are every 5 -20-100 years…’) are often based on recent figures. The historian’s approach aims to try to work over longer periods in order to be able to refine our assessments of the phenomena that may await us.

Flood recurrence forecasts are often based on recent figures. The historian’s approach aims to try to work over longer periods.

Have you already been able to draw conclusions at this level?

Not yet, because, with regard to the Vesdre valley, I realized that no study had yet been made on the subject. So I had to start with the quantitative aspect, that is to say by identifying all the floods – I have listed around a hundred since 1840 – and that took a long time. So the qualitative aspect, that is to say analyzing the importance of these floods in terms of overflow, will be for a second phase of research.

It’s a real investigative work, what are your sources, what did they tell you?

Sometimes you just have to look up. In the Meuse basin there are 260 flood markers. These are metal plates, placed on facades, which mark the maximum height reached by the waterways at different times. There is in particular one in Namur which shows the levels reached in 1880, 1926, 1740. These are memory elements which were used to warn people, to indicate to them, for example, that it would be preferable not to place their boiler in such place.

Other sources are postcards, photos, or old engravings, which show, for example, bridges built with buttresses, indicating that the river was impetuous. There are other clues: in Verviers, the houses have 3-4 steps to access the ground floor, which therefore means that we knew that there would regularly be 50 or 60 cm in the streets .

There are also urbanization plans. The historic heart of Verviers is on a hill which is 15 meters above the level of the Vesdre, so the first dwellings took shelter from the river. For the 19th and 20th century, the daily press is also a good source.

You speak of “memory elements” of these floods. However, we know that, unlike the heart of Verviers, much has subsequently been built in a flood zone. Have we somehow lost our memory?

Yes, we have forgotten, we have not learned the lessons of the past. We have lost the memory of risk. We have lost the memory of a very concrete relationship with the river.

We have not learned the lessons of the past. We have lost the memory of risk.

I often cite the example of Vaux-Sous-Chèvremont in 1998, where a resident complained of not having been warned of the rising waters. His neighbor, who died, was no longer there to raise the alarm: the latter had installed a siren on his roof, when the water rose, he switched it on and the inhabitants then knew that they had to bring up the furniture, etc.

So there are habits that have been lost. I think we are losing awareness of the dangers around us. It’s quite human, when you have a bad memory, you try to bury it, and after a while you forget its contours.

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Historical flood markers are signs in the landscape that inform all generations about phenomena that have occurred. This relationship to the river, this relationship to the flood, this relationship to risk, history must allow us to rediscover it.

But the floods of last July were all the same exceptional.

Yeah, when I see the vintage photos where the levels sometimes seem very, very high (but I can’t quantify them), I find it hard to believe the old timers who say they’ve never seen this. They probably, as I said, buried some memories.

But it’s true that, from a historical point of view, the July floods are exceptional in terms of their duration (normally the level drops after 9 or 10 hours, this time it lasted at least 48 hours) and the number of victims.

Going through the gazettes, since the middle of the 19th century, the greatest catastrophe that I have identified is the flooding of the Meuse in 1880, with 12 victims. Here we have about forty. The cause, is it the event itself or the loss of awareness of the risk, it is part of the reflections to have on risk prevention in the future.

What other insights have you been able to draw from your research?

For example, there are places that appear on a recurring basis. The place called La Brouck, which was much talked about in 2021, for example, appears systematically with each flood since the 19th century. This is also the case of the rue de la station in Chênée, or the meadows upstream of Verviers, near Dolhain.

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We thus have a series of places of which we can find traces. This should help to anticipate, to try to develop a culture of risk, to take into account a long past if we build or if we undertake an activity in such and such a place. So do we assume, do we not assume… It is not for me to comment but as a historian, I think I can bring to the public decision to come a certain number of elements.

Are there also lessons to be learned in terms of possible solutions to be implemented to fight against floods?

At the level of the Gileppe and Eupen dams, I was able to verify that indeed, as has been said, during their design, their main purpose was not to fight against flooding. For the Gileppe dam, the aim was mainly to regulate the river to prevent the textile industry from running out of water, and for the Eupen dam, the aim was above all to supply drinking water, to produce some electricity and also to regulate the river. But in use, we realized empirically that the Eupen dam, above all, could retain a little water during floods, and therefore we asked it to fulfill this function during the 20th century.

Otherwise, there have been major investments by the public authorities on the Ourthe, the Amblève, the Vesdre, or the Meuse. And we cannot say that they were useless. The works carried out in the 1960s on the Ourthe, for example, generated a certain satisfaction among local residents.

Afterwards, the question is to know if we can do something in the face of events that visibly exceed the standards, and if these events are likely to come back or not?

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