Updated 16 November 2020
"The purpose of this section is to manage activities related to flood hazards from intense rainfall, so that risk is not increased and is reduced over time.
The nature of risk and appropriate mitigation for rainfall related flooding can vary depending on the nature of the flood area. Council has therefore defined three types of flooding areas from intense rainfall events: floodplains, overland flowpaths and flood prone areas.
The purpose of these categories is to enable targeted control of activities which may introduce risk or negative effects, while allowing activities which may be appropriate in or adjacent to the flood area. This section adopts the 1% AEP rainfall event taking into account climate change and sea level rise to give effect to the Bay of Plenty Regional Council Regional Policy Statement.
Floodplains are situated next to a river or stream. They carry out the important function of water storage and flood flow conveyance during a flood event. Development within a floodplain can cause an increase in flood risk, by either placing more people and assets within an area likely to be affected by flooding, and/or by increasing flood flows through loss of storage and conveyance function and diversions of flows such that additional adverse effects occur.
Overland flowpaths are part of the stormwater system to safely convey flood flows, which cannot get into or cannot be conveyed by the primary stormwater system and need to be protected in order to reduce nuisance or damage caused by flooding. Overland flowpaths have been delineated into following categories:
- Minor overland flowpath: has a contributing catchment of less than 2ha.
- Major overland flowpath: has a contributing catchment of 2ha or more, meaning that the flowpath function serves a larger area. There is potentially greater onsite risk in a major overland flowpath and the possibility that the major overland flowpath will affect larger upstream and downstream land area than a minor overland flowpath.
Flood prone areas are areas which are flooded in a 1% AEP event, however, unlike floodplains and overland flowpaths, the flow of the water is much slower. Therefore, it is possible to develop in flood prone areas in certain circumstances provided flood risk to life and property is mitigated.
Council holds publicly available information showing floodplains, overland flowpaths and flood prone areas, which identifies the locations and extent of these flood types."
Plan Change 27 – Legal effect
Definitions in this section
"flood prone areas"
"major overland flowpath"
"minor overland flowpath"