24 January 2014

Floods alert in South-Est of France : interview to Emphoux and Aicardi (City of Antibes)

Floods, landslides, mudslides, fallen trees: southeast of France was hit hard by last weekend weather. Between 17th and 19th January it rained the equivalent of two months in several municipalities of the Var County.

In the nearby Alpes-Maritimes County, precipitations were monitored in real time by a dual polarisation X-band radar located on Mont Vial (Malaussène). We asked to Valérie Emphoux and Jean-Marie Aicardi from the City of Antibes Juan -les-Pins how this emergency was handled.

What were the consequences of these strong rainstorms in your territory and how your service has responded to this emergency?

Var coastal rivers have experienced significant flooding (Gapeau Argens, ...), but the County of Alpes-Maritimes was relatively spared. Here the severe weather conditions caused numerous landslides with roads cuts, but relatively few overflows and urban runoff.
Before and during the storms, we set up our standard procedure: Weather surveillance, triggering of mass phone calls server to inform the inhabitants in flood-prone areas during orange alert by Météo- France, alerting municipal teams, field monitoring, preparation of possible evacuations, etc.

In the end, there was no need to close roads or evacuate people last weekend (FYI a camping was evacuated during heavy rain a few days earlier).

A dual polarisation X-band radar provides the City of Antibes Juan-les-Pins detailed information on precipitations. What is the added value of this device in the management of flood risk, in particular during the recent rainstorm event?

As it was presented at the RainGain symposia in October 2013, this device is used to monitor rainfall evolution in real time (storm cell tracking, total rainfall, instantaneous intensity , ... ), and also with a 1 hour forecast lead time. It enables us to refine the hydrological analysis we do in real-time with our field observations (soils saturation, urban runoff, loading of stormwater sewer networks, ...) and measurement networks, and to better establish the decisions on urban civil protection response. After the rain event, it allows us to do a quick hydrological analysis.

You noticed a tendency of the residents to underestimate the risk of flooding. How a better perception of risks can support prevention and what is the role of communication and education?

Before the flood, the knowledge of phenomena (possible height and extent water rates ...) allows to study the mitigation measures to be implemented by the inhabitants. During the floods, a better perception of risks would allow residents to think about the safest course of action they should take, and to comply with the minimum safety precautions. After the flood, we can imagine that the "psychological" shock is less violent.

Communication and education are key components of prevention, but which require people involvement to inform and educate: this is the main difficulty. Certainly, there are many projects and ideas to be tested in this field, which is currently probably poorly understood if we consider witness statements after each flood.

To learn more about experience in urban flash-floods management from the City of Antibes read the presentation held on 23rd October 2013 by Valérie Emphoux and Jean-Marie Aicardi: Alerte et gestion des crues éclairs sur les petits bassins versants urbains.