Key proposed flooding changes for the new District Plan

12 March, 2020
  • Introduce newly mapped areas across the district that are at risk from flooding during a one-in-200-year flood event. These areas could have flooding at least five centimetres deep.
  • Show all mapped areas on a map in the Proposed District Plan as part of a Plains Flood Management Overlay. This means that for these areas in addition to the underlying zone rules, specific rules would also apply.
  • In line with the current practice, when there is a proposal to subdivide or build a new dwelling in an area at risk of flooding, a site-specific assessment would be required. The assessment would determine the required minimum floor height level of any new building.
  • The district-wide minimum building floor height would be 300mm above a 200-year flood level event (instead of the current requirement of 300mm above a 50-year flood level event). In practice this means the floor level for a new dwelling would need to be higher than is currently required, although the amount of that increase would vary from place to place, depending on local conditions. For the majority of properties, the increase is likely to be only a few centimetres more than what is currently required.
  • The site assessment would also look at whether the proposed building site meets the criteria for being in a ‘high hazard area’. If it does, then additional restrictions would apply. In some circumstances, where the flooding is particularly deep or fast-flowing, this may rule out building in that location.
  • For work on an existing dwelling in an area at risk from flooding, no resource consent would be needed, as long as any new floor is of the same height as the floor in the existing building, or is at least 300mm above a 200-year flood level.
  • For projects where the site assessment determines that the proposed building site is in a ‘high hazard area’, work on an existing dwelling would also still be permitted (ie no resource consent would be required), however the criteria would be slightly different:
  1. there is no increase in the floor area of the building;
  2. the building’s finished floor height is no lower than the finished floor height of the existing building; and
  3. any reconstructed or replacement building is in substantially the same position as the original.
  • To reflect the fact that a series of secondary stopbanks have been built along the Waimakariri River, the Waimakariri Flood Category A area would be amended so that:
  1. the land that is now protected by the secondary stopbanks is removed from the map, and
  2. the smaller area between the stopbanks where the high flood risk remains is renamed as the Waimakariri Flood Management Overlay.
  • Subdividing or building a new residential unit or other principal buildings within the Waimakariri Flood Management Overlay would continue to be a non-complying activity. This means that a resource consent would be required and would be difficult to get.

Categories: proposed changes, flooding, district plan review
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