Horo whenua Landslides

A landslide (sometimes called a “slip” or “landslip”) is formed by ground falling, sliding or flowing down a slope. Landslides may be made up of natural rock or soil, or artificial fill.

Landslides can range in size from a single falling rock to a very large avalanche of debris—with huge amounts of rock and soil spread across many kilometres.

Some landslides slip downslope in seconds without warning and can result in a loss of life, as there is not enough time to evacuate. Other landslides move slowly over many years, only causing damage to property and infrastructure.

Many landslides are caused by intense or prolonged rainfall, or the ground shaking in earthquakes. Increasing population, changing land-use and intensification increase the impact and costs associated with landslide events.

Landslides are one of the more common natural hazards to affect New Zealand homes and properties. They occur in rural and urban areas. Cyclone Gabrielle impacted the North Island of New Zealand in February 2023 triggering more than 800,000 landslides—this is one of the most extreme landslide-triggering events ever recorded.

Landslides cause more loss of life than any other geological hazard in New Zealand.

Landslide hazards can be divided into two broad categories: slippage and landslide runout.

• Slippage is the movement or loss of land from a slope when a landslide occurs beneath it (the landslide source area). 
• Landslide runout is the inundation of an area by rock, debris, soil, and other material that is travelling downslope from the landslide source area. This debris inundation can crush cars, buildings, and people, and move heavy objects.

The hazard associated with landslides is determined by its size, travel distance (runout) and speed of movement.

Landslides can also create secondary hazards. If landslides block streams and rivers, they can dam waterways. This may lead to the development of lakes upstream of the dam, and these can rapidly fail, releasing flood waters and debris down their catchments. This hazard is often referred to as a “dam-break flood”. Landslides that fall into water bodies, such as lakes, fiords and the sea can also generate tsunami.

Homes on or around unstable slopes and hills can quickly become damaged or unsafe if the ground moves. Damage can occur over time, as a result of slow-moving land instability, or quickly because of rapid slippage following an earthquake or intense rainfall.

Slow moving landslides can be disruptive and cause:

• cracks in your foundations, floors and walls
• uneven floors
• doors or windows to no longer close easily
• cracks or damage to retaining walls
• damage to outside features such as pulling away from the building, or diagonal cracks in plaster, brickwork, solid walls or foundations
• damage to underground infrastructure such as pipes

• Learn how to make your home saferopen_in_new
• Search your address in the Natural Hazards Portal to find out which hazards may affect your property.
• Read more about landslidesopen_in_new and how they can affect people and places.
• Check that you have the right insurance in placeopen_in_new, including home insurance that may qualify you for natural hazards cover.
• Check your local council website for information about local hazards and emergency planning in your area.