Land Instability

Land instability encompasses a range of ground movement hazards — landslides, slips, rockfalls, subsidence (ground sinking), and creep (slow downslope movement). New Zealand's steep terrain, seismic activity, volcanic soils, and high rainfall make land instability one of the most widespread natural hazards affecting property.

Many desirable properties in New Zealand are built on hillsides with views, but slopes bring inherent stability risks. Heavy rain events regularly cause slips across the country, damaging homes, roads, and infrastructure. The risk is heightened during earthquakes and after vegetation removal.

Councils map areas of known or suspected land instability in their district plans and LIM reports. Properties in these zones may face building restrictions, requirements for geotechnical assessments, and engineered foundation solutions. Even properties outside mapped zones can be at risk if they're on slopes, near watercourses, or on fill (imported soil used to level a site).

Land instability can cause catastrophic damage to buildings — from cracked foundations and tilting floors to complete destruction if a major slip occurs. Remediation of slip damage is extremely expensive and sometimes impossible. Properties on unstable land may be difficult to insure and hard to sell.

For any property on a slope, near a cliff face, or on filled ground, check the LIM report for land instability hazard overlays. Consider getting a geotechnical assessment, especially if you plan to build or modify the property. Look for visible signs of movement: cracked retaining walls, tilting fences, doors that don't close properly, or uneven floors.

The LIM report will flag known land instability hazards. Council GIS hazard maps show areas of identified slope instability. A geotechnical engineer can assess the specific risk for a property by examining the soil, slope angle, drainage, and geological conditions. During physical inspections, look for signs of past movement: stepped cracks in walls, misaligned door frames, retaining wall failures, and ground surface irregularities.