FLOOD-PROOFING MEASURES APPLICABLE TO STRUCTURES, UNDERTAKINGS AND WORKS IN FLOODPLAINS
Authorized structures, undertakings and works must comply with the following flood-proofing standards, adapted to the specific context of the infrastructure concerned:
1. no opening (window, cellar window, door, garage, etc.) may be lower than the 100-year flood elevation;
2. no ground floor is allowed at a level that is lower than the level of the 100-year flood elevation;
3. drains must have a non-return valve;
4. for any structure or part of a structure built below the 100-year flood level, a study must show the structure’s resistance to flooding and must include calculations relating to:
— structural stability;
— reinforcement necessary;
— seepage water pumping capacity; and
— resistance of the concrete to compression and tension;
5. the filling of land should be restricted to protecting the area immediately around the structure or undertaking concerned and should not extend to the entire landsite; the average slope downward from the top of the fill next to the protected structure or undertaking should not be less than 33⅓% (vertical to horizontal ratio of 1:3).
When implementing flood-proofing measures, if the 100-year flood elevation was not established at the time the limits of a mapped floodplain were delineated, the elevation of the highest reference floodwater level should be used to replace the 100-year flood elevation in determining the limits of the floodplain, to which 30 cm should be added for safety reasons.