Floods constitute a major risk over the national territory as well as Europe and the entire world.
In France, flood risk affects one in three towns (i.e. approximately 14,000 towns) on various scales, including 300 large conurbations. For 160,000 km of major rivers, a surface area of 22,000 km2 is considered a flood risk area: four million residents are concerned. The damage caused by floods represents a little over half of the cost of the damage due to natural hazards, i.e. over €300 million each year. Half of this amount relates to economic activities.
Due to economic, social, land or political pressure, rivers have often been developed, covered or diverted, thereby increasing the vulnerability of people and assets.
To remedy this situation, improving flood forecast and prevention remains the State’s primary tool, who should focus on improving the provision of information to the population exposed and reducing the vulnerability of assets located in flood risk areas, especially when certain sites need to be near water to operate. Amongst existing challenges, high-risk industrial installations under the legislation on classified installations should not be neglected as they can be strongly affected by floods, in particular sites in the Ile-de-France region, by the river Rhône, in the Gard department, on the Ambès peninsula etc. In addition to the malfunctions and internal damage to the facilities caused by flooding, there is also a risk of triggering cascading events within the facility, the combination of which would result in an industrial accident aggravating the consequences of the flood for the population.
The law relative to classified installations of 19 July 1976, reiterated in the environmental code, and its implementing decree of 21 September 1977, requires the establishment by the operators and under their own responsibility of a risk assessment. The risk assessment constitutes the basis for the prevention of industrial accidents. In this report, the operator must examine the status of his installations with regard to flooding hazards and determine and implement all necessary and sufficient measures to control the risk of accident due to flooding.
2Risk analysis / Risk assessment / Best available technologies2
The method used to take account of flood hazards in a risk assessment is similar to the one used by the operator to take account of any event likely to contribute to an industrial accident scenario.
Operators methodically begin their risk assessment by characterising all potential hazards, listing those inside as well as outside the facility, in particular natural dangers including floods.
During this inventory, operators should not prejudge the results of the risk assessment process leaving out any information liable to contribute to the risk analysis. They must therefore specify, more than by a mere statement, the information relative to the site’s flood risk. In their risk assessment, operators must explicitly specify the water level that the basic-stage flood may reach in different areas of the site. The basic-stage flood therefore constitutes an entry data which, although inaccurate, is available resulting from the analysis of previous floods. It represents the reference parameter to assess the risks of industrial accidents associated with a flood in classified installations.
On the grounds of this entry data, operators must determine whether the installations of their plant are located in areas which may be affected by flooding.
If, based on this entry data, operators determine that their site may be subject to flooding, they must include flood hazards as entry data in their risk analysis.
The establishment of the risk assessment then follows the methodology and logic mentioned in the guide of the Ministry for Ecology, Sustainable Development and Spatial Planning.
Operators should use the technical information published by Ineris for greater efficiency, as it constitutes a good scientific summary. It is also of practical use as it provides background information for the detailed analysis of the risks as well as tools for adapted prevention and protection measures.
Following this evaluation approach, operators should determine, in their risk assessment, all technical and organisational safety barriers to reduce and control the risk of accident due to flooding.
Environmental code: art. L. 512-1 (risk assessment)
Article R512-6 of the environmental code (risk assessment)
Ministerial order of 10 May 2000 relative to the prevention of major accidents involving hazardous substances or preparations present in certain categories of permit holding classified installations for environmental protection
Ministerial order of 2 February 1998 relative to the water withdrawal and consumption as well as all types of emissions of permit holding classified installations for environmental protection, in particular chapter II
Sectorial ministerial orders reiterating the general requirements of the ministerial order of 2 February 1998.