Coastal Erosion

Visit the Coastal Erosion Map to find out whether the latest information the Council holds indicates your property may be susceptible to coastal erosion.

The maps show areas that may be susceptible to coastal erosion in the present day and for future times (2050, 2080 and 2130) under different climate change scenarios.

Please note that the studies on which the mapping is based are of regional scale and are indicative only of coastal erosion affecting any individual site or property. If detailed information about a specific property is required, a qualified professional will need to carry out a site-specific assessment.

Natural hazard maps change as our environment changes and our knowledge evolves. This is the first time that a coastal erosion map has been produced for Council. It identifies areas that are potentially susceptible to coastal erosion and reflects our most up-to-date understanding based on the latest information available to us.

Please note that the studies on which the mapping is based are of regional scale and are only indicative of coastal erosion affecting any individual site or property. If detailed information about a specific property is required, a qualified professional will need to carry out a site-specific assessment.

Natural Hazards information is used to inform planning, building, and resource consent processes.

Before starting any development, check the Nelson Resource Management Plan (NRMP), National Environmental Standards developed under the Resource Management Act 1991, and the Building Act 2004 to confirm whether a consent is needed. If a consent is required, natural hazard information will be considered through the resource and building consent processes.

The studies on which the mapping is based are of regional scale and are only indicative of coastal erosion affecting any individual site or property. If detailed information about a specific property is required, a qualified professional will need to carry out a site-specific assessment.

It is possible that larger events than those mapped (such as beyond the 1% AEP scenario) could occur, or that future changes alter the likelihood of coastal erosion.

The natural hazards webmaps show the latest information we have on a range of hazards, including coastal erosion. This information can support planning and raise awareness of natural hazards in the region. As new information becomes available, our understanding of coastal hazards in Nelson continues to improve and this information can be used to inform updates to our website.

Meanwhile, maps/overlays and related planning provisions for natural hazards exist in the NRMP, but not specifically for coastal erosion. The NRMP is a statutory plan under the Resource Management Act 1991 and can only be updated through a formal plan change process. A future plan change may introduce provisions relating to coastal erosion or this could be included in a new plan that replaces the NRMP.

Coastal erosion hazard distances are calculated based on a number of factors that influence the overall erosion process. Information used in the analysis includes:

• Shoreline type (i.e. cliff, estuary bank, sandy beach, or gravel beach).
• Historical and current shoreline data from aerial photographs.
• The profile of the beach and land elevation (topography) sourced from LiDAR survey (land elevations) and depth of the nearshore seabed (bathymetry) sourced from hydrographic charts.
• Extreme water level and wave exposure modelling.
• Projected sea level rise from the NZ Sea Rise platform.

Coastal erosion distances are calculated and mapped for a range of timeframes and climate scenarios. Further information can be found here.

These areas are excluded as there is not yet enough understanding of how long-term coastal erosion may interact with structures such as the sea wall. This part of the coast has been significantly changed by land reclamation and protection structures. Because these changes are so extensive and have been in place for so long, we cannot use old data to estimate what the long-term erosion rate would be in the absence of these structures.

P50 means that there is a fifty percent (50%) chance that coastal erosion under the chosen sea level rise scenario and timeframe will be less severe, and a fifty percent chance the outcome will be more severe, than what is mapped. This can be considered a likely projection.

P5 (5th percentile) means that there is only a five percent (5%) chance that under the chosen sea level rise scenario and timeframe, the outcome will be more severe than the coastal erosion predicted, and a ninety five percent (95%) chance that coastal erosion will be equal to or less severe than this. This can be considered a more extreme though still possible, erosion projection.

These projections are provided on - NZ Sea Rise Our Changing Coastline and relate to sea level rise projections.

P50 means that there is a fifty percent (50%) chance that the sea level rise projection under the chosen climate scenario will be exceeded, and a fifty percent chance that sea level rise will be less than projected.

P83 (83rd percentile) means that there is an eighty-three percent (83%) chance that the sea level rise projection under the chosen climate scenario will be equal to or less than this, and a seventeen percent (17%) chance that the projected sea level rise will be exceeded. A P83 projection represents an unlikely though still possible, projection.