LANDSLIDES

For better or for worse Gisborne/Tairawhiti is the landslide capital of New Zealand. This is the result of a combination of a range of factors including its young weak sediments, steep slopes, severe high intensity storms and rapid tectonic uplift. The region is adjacent to the Hikurangi plate boundary where the Pacific crustal plate is pushing under the region causing frequent earthquakes (see below) but is also resulting in the land uplifting. The hills are not getting higher, however, as the landsliding is a natural response. 

Landuse is also having an impact, however, and where the natural indigenous ground cover remains we see few landslides and those that do occur are generally smaller in scale than in areas of other landuse. Recent experience has shown us that landslides are severe in exotic forested areas that have been recently harvested. Ironically, since many of those exotic forests were planted for land stabilisation purposes after Cyclone Bola. Pastoral farmlands on steep hill country is also prone to shallow landslides. Many of these will be quite small but in severe storms such as Bola or Gabrielle, many landslides will still occur.

The main triggers for landslide activity are severe storms but also large local earthquakes but sometimes some larger landslides such as the very large valley damming landslide at Mangapoike in 2018 or the Te Kuri a Paoa/Young Nicks Head landslide in 2024 have occurred without any obvious triggering event.

Slope instability can be caused by heavy rain, earthquakes, vegetation removal, leaking pipes and earthquakes. Slope instability can cause landslides to occur when the strength of the slope is overwhelmed. Landslides can damage land, property and infrastructure such as roads, railways and communication systems.

If you know you are in a landslide hazard area:

Keep an eye out for the warning signs on your property. Contact your Council or engage a geotechnical engineer if you notice:

• Small slips, rock falls and subsidence at the bottom of slopes.
• Sticking doors and window frames or gaps where frames are not fitting properly.
• Steps, decks and verandas moving or tilting away from the rest of the house.
• New cracks or bulges on the ground, road, footpath, retaining walls and other hard surfaces
• Tilting trees, retaining walls or fences.

What to do if a landslide is happening:

• If a landslide is happening, or you think a landslide is going to happen, get out of the way quickly. 
• Evacuate if your home or the building you are in is in danger — take your Grab Bag and pets with you if you can do so quickly. 
• Warn neighbours and help others if you have time. 
• Look to connect with emergency services or your local council for updates and information.