By definition, floodplain represents the land surface that is submerged by a watercourse when it overflows its bed. "Many factors affect the flow of a river, and therefore the risk of flooding. Among the most important are the amount and type of rainfall, the nature and condition of the watershed, and the climate "(Government of Canada).
Damage to buildings
The floods cause considerable material damage to buildings in flood-prone areas.
Here are some examples of damage caused by floods:
- Slab on damaged soil due to high hydrostatic pressure;
- The appearance of star-shaped cracks in the slab on the ground;
- A structural movement in the foundations;
- The subsidence of the building;
- Rot in the wooden structure; etc.
Municipalities require foundations to be water-repellent when a building is located in a flood-prone area (floodplain). Water-repellent foundations imply that the concrete foundation must have thearmature necessary to resist the hydrostatic pressure that would cause a flood. The entire external surface of the vertical part of the foundation - located below the flood level - must be covered with a water-repellent membrane based on rubberized asphalt.
In addition, the floor of foundations must be built with a base counter-slab (cleanliness slab), the surface of which is covered with a water-repellent membrane based on rubberized asphalt.
In short, the foundations, the footings, the slab on the ground - in the system of water-repellent foundations - must be well waterproof and waterproof. This type of system must not allow water to enter the basement, despite the high hydrostatic pressure that is practiced against these elements.
After flooding a building, the authorities request that a civil engineer visit the property to assess the damage and propose the appropriate solution for the necessary corrections.