The various types of flood

There are three types of flood :

• The slow rise of water in plain areas. This occurs when a river slowly leaves its minor bed or when the water table rises after several rainy years.
• Run-off, which is frequently worsened by surface sealing (urban sprawl, agriculture). Surface sealing often causes the saturation and overflow of the drainage networks.
• The quick formation of torrential floods.

The effects of flooding on industrial facilities

In addition to the risk of personnel being drowned, the damage caused to personal belongings and real estate is often sizeable. Finally, the consequential damage (loss of activity, layoffs etc.) is often greater than the direct damage caused by flooding.

Neither must the risks of water and soil pollution caused by flooding be neglected, when the site involves the storage of hazardous substances :

• loss of confinement of storage tanks (under- or above-ground),
• overturned pallets stored on the ground or in racks,
• burst drain pipes,
• fires caused by flooding (for example due to short-circuits),
• explosion further to the loss of containment of flammable liquids/gases,
  hazardous exothermic reactions in the presence of substances incompatible with water,
• injuries caused to third parties by products or debris carried off by the floods
• etc.

Regulatory background

In accordance with article R 512-9 of the French Environmental Code, risks, including those of external origin, must be taken into account in the hazard studies. This is the case for the flood risk in particular.

For the classified installations subject to authorisation, a complementary hazard study can be prescribed pursuant to article R 512-31 of the French Environment Code if the flood risk is insufficiently taken into account.

Our initiative in the flood risk analysis