flooding hazard notice building consent assessment process[1]
DESCRIPTION
New document from CouncilTRANSCRIPT
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Floor levels in residential homes in Christchurch Guidance.
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Guidance on Building Consent assessment process, of rebuilds in
the Flood Management Area to ascertain:
If a Flooding Hazard notice is required?
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Overview Only• This Powerpoint is an overview only.• We are more than happy at the end of
this presentation to answer any questions that you may have.
Got any sandbags?
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Terminology• Interim Floor Level – the minimum floor
level for a new building or if significant extensions are required.
• Average (mean) Ground Level – average ground level on the site as determined by the latest ground surface information.
• Building Platform- Is the 1:50 yr ground level without the 400mm freeboard added.
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Terminology-cont• Min Ground Level – minimum ground level on
the site as determined by the latest ground surface information.
• Max Ground Level – maximum ground level on the site as determined by the latest ground surface information.
• Freeboard- 400mm added to the 1:50yr or 1:200yr level. Freeboard is a provision for construction tolerances, waves, bend effects, etc
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Terminology-cont• Floor Level Control Areas - are within and
adjacent to the 50 year and 200 year flood extents. The Council applies a 400mm freeboard to floor levels in these areas.
• Water levels and ground levels - are expressed in metres above the Council’s datum level. This datum level is about nine metres below Mean Sea Level. So a level of 10m above the Council’s datum is about one metre above Mean Sea Level.
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Full Foundation Repair and RebuildAnnual Excedence Probability (AEP)
In Flood Management Area, (FMA).City Plan RMA (0.5%AEP)1:200yr).
&In the Flood Zones, Building Code
E.1.3.2 (2%AEP) 1:50yr).
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Building Act. (E.1.3.2)
• 2004 Building Act Flood Zones(2%AEP) 1:50yr). Annual Excedence Probability.
• Flood extent (50 year) – estimated water level in a rainfall event with an average return interval of 50 years or a likelihood of 1/50 (=2%) in any one year.
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Resource Management Act. (City plan)
• Resource Management Act, (City Plan) (0.5%AEP)1:200yr).Annual Excedence Probability.
• Flood extent (200 year) – estimated water level in a rainfall event with an average return interval of 200 years or a likelihood of 1/200 (=0.5%) in any one year. This return interval is used in the City Plan Flood Management Areas (FMA) to provide extra protection to areas which are otherwise vulnerable.
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Flooding Website.
• The Flooding website address is http://maps.cera.govt.nz/advanced-viewer/?Viewer=Ccc-Floor-Levels
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Flooding website screen shot
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Consent in an FMA, or Flood Zone-Conthttp://maps.cera.govt.nz/advanced-viewer/?Viewer=Ccc-Floor-Levels
• E.G. (example from website)• Interim Floor level 12.27M• Average Ground Level 10.78M• Modelled 50 year Flood Level 11.72M(1:50yr without freeboard is Building Platform level).• Modelled 200 year Flood Level 11.87M• Subtract 10.78m – 11.72m=
940mm flooding to land.
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To avoid a hazard notice?• You need to do two things E.G.• One: Build/ Raise the house to
a set Finished floor level. • Two: Mitigate the flooding to
land.• Mitigation: can be done by filling the site,
damming the site boundary, water retention tanks & pumps, stop banks, etc.
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To avoid a hazard notice-Cont(using the example)
• You need to do two things E.G.• One: In the FMA, Build the house with a
Finished floor level of 12.27M• Two: Mitigate the 940mm of flooding to
land.• Mitigation can be done by filling the site,
damming the site boundary, water retention tanks & pumps, stop banks, etc.
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Processing a Consent in an FMA,or Flood Zone.
• If you are Building a house in the FMA or Flood Zone as indicated in the Development report or PIM.
• Please check that the proposed floor level for rebuilds or new housing are at the required level & then check the flooding to land by subtracting the 1:50 year (building platform level with-out the freeboard), from the average ground level.
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Consent in an FMA, or Flood Zone-Cont
• If you then find that the flooding to land is close to of more than 400 mm then a Hazard notice under Section 71 to 74 of the Building Act 2004 may apply.
• Hazard notice, if flooding to land can not be mitigated.
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Areas over 400mm of flooding
In Red areas of flooding over
400mm
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Building Act.– What is Section 71-74?
• Building on Land subject to natural hazards.• Natural Hazard means
– Erosion (including coastal erosion, bank erosion, & sheet erosion).
– Fall debris, subsidence & slippage.– inundation (including flooding, overland flow,
storm surge, tidal effects & ponding.
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Building Act.-Cont– What is Section 71-74?-cont
• Section 71 of the Building Act 2004, provides that a building consent must be refused for work on land subject to certain natural hazards unless the Council is satisfied that the land, building work, or other property will be protected.
• An application required to be refused under s71 must nevertheless be granted under s72.
• If the building work will not accelerate, worsen, or result in a natural hazard on the land on which the building work is to be carried out or any other property.
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Building Act.-Cont
– What is a Hazard notice & when may that apply?
• A hazard notice is issued under section 73 of the Building Act.
• The registrar-general of Land must record , as an entry on the certificate of title to the land on which the building work is carried out.
• The natural hazard concerned must be identified.
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ANY QUESTIONS ?HELP