Should we fear floods like July 2021 due to the passage of ex-Hurricane Kirk in Belgium?

In anticipation, the Royal Meteorological Institute has also placed the provinces of Luxembourg, Liège and Namur on orange alert until late Thursday morning. Hainaut, Walloon Brabant and Brussels are under yellow vigilance.

Storm Kirk: ten rivers could overflow in Wallonia, the alert phase initiated preventively

The number 1722 has also been activated for non-urgent firefighter interventions in the event of storm damage or water damage.

Floods: what steps should you take for your insurance?

What do we know about Storm Kirk? Should we fear floods like those of July 2021? When will the peak precipitation occur? When will the situation return to normal? We take stock of the situation with Xavier Feittweis, professor of climatology at ULiège.

What do we know about this Kirk storm?

It’s an old hurricane that crossed the Atlantic and is dying as it reaches us. The main problem is not the wind. There will barely be any. It is rather the almost continuous precipitation that we will experience for 24 hours.

Why does it fall in the form of continuous rain?

The ex-hurricane brings with it an atmospheric river, an air mass very loaded with humidity. You really have to see it as a river on the ground, but in the atmosphere. This mass of air transforms into precipitation here, upon contact with the colder continent.

The atmospheric river, instead of crossing our country in width, crosses it in length. It extends over several hundred kilometers. It will therefore take time to pass through Belgium. Which explains why we will experience almost continuous precipitation for 24 hours.

Why is the southeast mainly affected?

The storm is coming to us from the south. The Ardennes, with its reliefs, will block precipitation. The regions south of the Hautes Fagnes and the province of Luxembourg will be copiously watered, followed by the other Liège regions. The regions to the left of the Meuse should be affected to a lesser extent. Beyond Brussels, there should not be much precipitation.

Is there a risk of flooding?

Thunderstorms are likely to develop in this front, as this air mass is very unstable. Between 50 and 100 l/m² are expected. This is not exceptional, but it is enough to generate localized flooding.

In places where 100 l/m² falls, it will be the equivalent of a month of precipitation in 24 hours. In these areas, it is certain, there will certainly be flooding. This will especially be the case for small rivers and in small valleys, because the rains will fall quickly over time. In areas where 50 l/m² will fall, the risk of flooding should be less.

Should we fear floods like those of July 2021?

Rest assured, the situation has nothing to do with the floods of July 2021, where we had 200 l/m² over three days. Here, it will be a maximum of 100 l/m² over 24 hours.

In July 2021, the depression was stuck in place. The front no longer moved. There was no wind. Here, the situation is more dynamic, since it is a former hurricane. But, problem: the front crosses the country along the length, and not across the width, otherwise the precipitation would have passed in a few hours and we would not have had much.

Despite this long crossing, there should not be any major flooding, except in the event of major storms. At that time, there could be significant flooding locally. In any case, it will not have the magnitude of July 2021, when the entire Vesdre valley was flooded.

What will be the most critical moment?

The peak of precipitation will occur tonight. The risk of flooding will be at its maximum Thursday morning. This is when small streams will be at their most problematic. A priori, the Meuse, for example, should not be too impacted.

Then things will calm down. The depression will shift and our country will move into anticyclonic conditions, with good weather.

Are we likely to see other storms soon?

Cyclone activity has just started quite strongly in the North Atlantic. There have been two hurricanes recently, Helene and Milton. All these hurricanes always end up dying in one way or another towards our regions. We are therefore not safe from a future storm. But which one and when? It’s still too early to tell.

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