InSAR monitoring of slopes to build back safer

Landslides are a significant natural hazard in Aotearoa New Zealand, causing major damage to property and infrastructure and, historically, more fatalities than any other natural hazard. Many parts of the country are vulnerable because of steep terrain, wet conditions, and land-use changes, yet slow-moving slope instability can be difficult to detect before failure occurs.

This report investigates whether satellite-based radar monitoring, known as InSAR, can help identify subtle ground movement across large areas and support better understanding of landslide risk in places such as Auckland and Gisborne.

Using satellite data from the European Space Agency’s Sentinel constellation, the project detected small-scale slope movements in all study areas, including Muriwai and Karekare in Auckland and suburban Gisborne.

The findings show that rainfall can temporarily increase slope movement, and that seasonal shrinking and swelling of clay-rich soils can also be detected from space. These results demonstrate the potential for InSAR to contribute to landslide monitoring, planning decisions, future early warning approaches, and practical guidance such as foundation design requirements in areas affected by unstable ground.