Natural hazards

Acid sulphate soils are naturally occurring, having been deposited when the sea level was around 5 metres higher than it is at present, 5 to 10 thousand years ago.

While the land was under the sea, salts in the seawater mixed with this land. Now that the sea level has dropped this land which was under the sea and mixed with salty sea water is now available for use. 

Areas that are known to have acid sulphate soil are shown on our GIS maps. You can read more about this phenomenon on the following page:

Acid sulphate soil planning policy

Erosion, landslips and sea water flooding are the dominant natural coastal hazards along the District's coastline.

Coastal erosion is either a long-term trend or a significant short-term shoreline fluctuation, especially on sand dune-backed coasts. 

Landslips are directly associated with coastal erosion where the geology is relatively weak and prone to slope failure.

Severe coastal storms or tsunamis produce waves which can temporarily flood low-lying coastal areas. The effects of climate change are likely to increase hazards in the coastal zone.

Coastal hazards reports

Coastal Management Strategy

Review of Coastal Hazard Zones for Eleven Selected Beaches(PDF, 2MB)

Coastal Hazard Risk Zone Assessment for Pataua and Matapouri Bay(PDF, 4MB)

Coastal Erosion Hazards Review - One Tree Point to Waipu Cove(PDF, 597KB)

Projected Sea Level Rise - Ruakaka and Marsden Point(PDF, 2MB)

Coastal Hazard Zone Assessment for One Tree Point and Marsden(PDF, 1MB)

Coastal flooding and coastal erosion

The Northland Regional Council manage the coastal hazard maps for coastal flooding and coastal erosion.  

In April 2021, the Northland Regional Council released a new update to the coastal flooding and coastal erosion maps.   

Update to coastal hazard maps (nrc.govt.nz)

Tropical storms and high rainfall intensities  expose many areas to flooding. There are obvious floodway areas plus areas that are susceptible to ponding. 

The flood mapping is used in the assessment of applications for resource consent and / or building consent.

Flood Susceptibility Mapping Report 2001(PDF, 1MB)

Waipu Cove Flood Management (2015)(PDF, 2MB)

Northland Regional Council update to river flood maps 

In November 2021, the Northland Regional Council released a new update to the Northland's region-wide river flood maps. 

Update to river flood maps (nrc.govt.nz)

Region-wide river catchments analysis - technical reports (nrc.govt.nz)

Geological characteristics and soil types in the District mean that some areas some areas should be developed carefully, and may require substantial works to avoid, remedy or mitigate land instability hazards. 

Inappropriate earthwork activities and / or the removal of vegetation also contribute to land instability. 

Land stability reports

Urban Land Stability Hazards for Kamo, Maunu, Onerahi, Otaika and Tikipunga(PDF, 386KB)

Urban Land Stability Hazards for Hikurangi, mid-Kensington, Whangarei City Centre and East Kamo(PDF, 836KB)

Urban Land Stability Hazards for Kensington, Morningside and Port(PDF, 203KB)

Coastal Slope Instability Hazards for Oakura to Langs Beach(PDF, 549KB)

Landslide Susceptibility Technical Report 2020(PDF, 8MB)

Liquefaction is a natural process where earthquake shaking increases water pressure in the ground in granular soils, resulting in temporary loss of soil bearing capacity. Liquefaction commonly leads to buildings ‘sinking’ on their foundations during the shaking – in line with that experienced in the 2011 Canterbury earthquakes.

Tonkin & Taylor Ltd (T+T) was engaged by us in April 2020 to undertake a liquefaction vulnerability assessment. The work comprises risk identification and analysis of liquefaction hazard in accordance with the Ministry of Building, Innovation and Employment (MBIE) and the Ministry for the Environment (MfE) Planning and engineering guidance for potentially liquefaction-prone land (MBIE/MfE, 2017) to help inform decisions about future development of land and buildings.

Building Consent applications must include consideration of the liquefaction risk of the subject property as part of the site suitability report.

Liquefaction hazard mapping report(PDF, 27MB)

Coal mining was formerly a major industry in Northland and major coalfields were located at Kamo and Hikurangi, both of which are now urbanised. Hazards such as subsidence, sink hole formation and unstable fill restrict development in these areas.

A geotechnical report is required for development withing areas of mining subsidence.

Mine zone reports

Mine Subsidence Hazard - Hikurangi Area(PDF, 242KB)

Mine Subsidence Hazard - Kamo Area (2013)(PDF, 2MB)

Mine Subsidence Hazard - Kamo Area (2005)(PDF, 307KB)

Kamo Mine Zones Map (March 2005)(PDF, 1MB)