The Council sets minimum floor levels to protect buildings throughout the city from the risk of flooding. If you are building, rebuilding or extending, your building may need to be built to the new floor level requirement.
The floor levels have been assessed based on the best available flood model information with the addition of a margin known as freeboard. Freeboard is the term given for an allowance in floor levels above the modelled flood level, which allows for modelling inaccuracies, construction tolerances, network failures and natural environmental factors such as wave and wind effects. All local authorities have a freeboard level; this tends to vary from 300 millimetres to 500 millimetres . Freeboard in Christchurch has been 400 millimetres above the flood level for many years. If you wish to propose a different freeboard for your building this will require a technical justification to be processed.
It is important to remember Christchurch is a generally flat, low-lying city and there have always been areas prone to flooding. The Council has always set minimum floor levels in these areas and updates these as new information becomes available. The Council is also working to mitigate the risk of flooding, having already raised stop banks in the worst affected areas close to the rivers, and has a land drainage recovery programme in place.