Flood management

High flood hazard management areas (HFHMA) are identified in the Christchurch District Planning maps.

High hazard areas are defined in the Canterbury Regional Policy Statement as flood hazard areas subject to inundation events where the water depth (metres) x velocity (metres per second) is greater than or equal to 1, or where depths are greater than 1 metre, in a 0.2% AEP (1 in 500-year) flood event.

These are areas at risk in a very large flood (a 1-in-500-year flood event) due to the depth and/or speed of flood waters. They are generally low lying land near rivers and/or close to the coast.

The flooding can be due to a combination of high rainfall events, rivers breaking their banks and/or tidal inundation (due to storm surges and high tides).

The residential unit overlay applies to residentially zoned parts of the high flood hazard management areas where the main flooding risk in the future will be from the sea, when storm events coincide with high tides, rather than flooding from rainfall or rivers.

The risk of coastal inundation, or tidal flooding, will increase over time this century with sea level rise. This applies to parts of New Brighton, South New Brighton, Southshore and Redcliffs.

The Christchurch District Plan considers the level of risk when managing development, including subdivision, in areas subject to natural hazards:

• The plan’s approach is based on avoiding development in areas where the risks from natural hazards to people, property and infrastructure is assessed as unacceptable. This includes risks from flood events, cliff collapse, rockfall, and mass movement. In these areas, where risks cannot practically be reduced to acceptable levels, the plan discourages new development.
• In areas where the risk from a natural hazard may be able to be managed to acceptable levels, development is allowed where it can be shown that the risk is able to be appropriately mitigated.
• The plan does not manage areas where natural hazard risk is similar to the level of many everyday risks that people face and accept.

High flood hazard management area

The plan states that new development in high flood hazard management areas is to be avoided where it will increase potential risk to people’s safety, well-being and property. This means not increasing density of development and not allowing new development that would place more people and property at risk in the most flood-prone areas.

Most new buildings and subdivision are non-complying activities, meaning that resource consent is likely to be declined. There are some activities that are permitted such as repair of existing buildings, or replacement of buildings where they are a similar size and location as existing buildings.

Residential unit overlay

Within the residential unit overlay new residential buildings or additions require resource consent as a restricted discretionary activity.  In certain circumstances new development may be consented where appropriate mitigation can be provided to protect against unacceptable risk.

Some activities are permitted without a resource consent, such as replacement or repair of existing residential units. Subdivision is a non-complying activity and as with subdivision in the High Flood Hazard Management Area, any resource consent will be assessed against a policy direction to avoid where it will increase potential risk to people’s safety, well-being and property.

Check if a property is within a high flood hazard management area or the residential unit overlay.

If you’re looking to build, redevelop or alter a building on land that is within a high flood hazard management area or the residential unit overlay, we encourage you to contact our resource consent team or duty planner on 03 941 8999 to understand how these rules apply to the property. 

If you are looking at purchasing land or a property, we strongly encourage you to request a LIM(external link) and have it reviewed by a lawyer to check the land use rules on that property.