Weather Alert: Red alert for floods and floods in Pas-de-Calais

From Monday November 6 at 4:00 p.m. to Wednesday November 8 at 6:00 p.m.

Situation

Oceanic disturbances have followed one another over the last few days over France under the influence of a very dynamic west to southwest regime. The cumulative rainfall was particularly abundant in Pas-de-Calais and New Aquitaine. The soils are saturated and no longer absorb the precipitation which will swell the waterways, causing floods and floods. Over the next few days, the disturbances will be more spaced out and less active but they will continue to circulate over the west and north of France, delaying the recession of the rivers.

According to the Vigicrues organization, the flood of the Aa is exceptional, potentially exceeding the historic flood of 2002. The safety rating of the Blendecques containment system risks being exceeded and a point of attention must also be paid to the dykes of the Haute Meldyck in the crossing of St Omer.
Damaging overflows are underway. The flood will spread downstream to Wizernes where widespread overflows are expected during the night from Monday to Tuesday.

Observation

This Monday at 6 p.m., the lull is confirmed in terms of precipitation in Pas-de-Calais. Only a few rare showers circulate in a very scattered manner, without consequences. The flood of the Aa continued with a rise in water of one centimeter per hour at the Flandres Aval station (level at 2.74 m at 5 p.m.). In Lumbres-Blequin a historic flood was observed at 2:15 p.m. with a level of the Aa at 1.86 m exceeding the reference flood of March 2002.
In the center-west, showers were still frequent, but generally of less intensity than in recent days. The rivers placed on orange alert showed a high water level but gradually stabilizing, or even a slight decline for some of them.

At 13h, a relative lull was observed on the precipitation front in Pas-de-Calais between the Opal coast and the Boulonnais hills after the heavy rains of the night and morning. Over the last 24 hours, 30 mm fell in Beighen, 32 mm in Attin, 37 mm in Le Touquet, 44 mm in Steenvoorde (59) and 27 mm in Nielles-les-Bléquin. These heavy rains cause flooding of the Lys, the Aa, the Hem and the Liane. Flooding is observed in places. In New Aquitaine, the showers continue to come one after the other, sometimes taking on a stormy character. Rainfall accumulations are heterogeneous but locally reach 25 to 30 mm in 24 hours. They come in addition to the significant accumulations of rain in recent days. Floods mainly concern the Charente, the Boutonne upstream, the Seugne, the Sèvre Niortaise, the Dronne and the Isle.

Evolution

This Monday, the weather remains unstable in Pas-de-Calais as well as in Nouvelle-Aquitaine with sometimes sustained showers. Total rainfall during the day can reach 10 to 20 mm in New Aquitaine and up to 30 mm in Pas-de-Calais.

Tuesday, new precipitation in the form of rain or showers concerns New Aquitaine and Pas-de-Calais with less rainfall totals than in recent days. The accumulations will generally be between 5 and 10 mm, locally 15 to 20 mm. Some rivers may begin to recede.

Wednesday, New Aquitaine will benefit from a respite and a few hours of dry weather, before the arrival of a new ocean disturbance at the end of the day. Pas-de-Calais will see the ocean disturbance arrive in the morning with moderate rain for a good part of the day this Wednesday. After a decreasing trend on Tuesday, new floods could occur from Wednesday afternoon.

List of departments concerned