Liquefaction map

We’ve developed a liquefaction map viewer which classifies areas in the District according to the following liquefaction vulnerability categories:  

• Liquefaction Damage is Possible – areas where the geologic setting suggests that the underlying sediments may contain units that are susceptible to liquefaction. 
• Liquefaction Damage is Unlikely – geological units considered not susceptible to liquefaction based on their geologic description and/or depositional setting. 
• Very Low Liquefaction Vulnerability – where there is sufficient conclusive geological information that the underlying deposit is not susceptible to liquefaction (e.g. shallow rock and fractured rock comprising landslide deposits in mountainous areas). 

Methodology 

The methodology used to develop the liquefaction information shown on the liquefaction map viewer is described in the accompanying report:  Tasman Regional Liquefaction Assessment (2021) (pdf 24 MB) 

The mapping was undertaken at a regional level (‘Level A’ criteria)  following MBIE’s 2017 Guidance. It is based on published geological information as well as LiDAR ground elevation data and groundwater level data.  The mapping does not include site specific subsurface investigations which are part of more detailed assessments (Level B-D mapping criteria). 

Read more about the planning and engineering guidance for potentially liquefaction-prone land on MBIE’s website.  

The areas mapped as ‘liquefaction is possible’ do not necessarily mean liquefaction will occur across all these areas. In fact, the gravelly nature of Tasman’s alluvial plains are such that incidences of liquefaction will be much more limited in extent, but there could be “pockets” of liquefiable fine grained sands and silts within these areas (such as an old, infilled and buried river channel). The uncertainty of where such areas are located results in them being mapped as ‘liquefaction is possible’.  Estuary and coastal margins are often vulnerable to liquefaction. 

See the tips below on how to get the most out of the map. You can open the map viewer in a new window.