A National Landslide Dam Database for New Zealand

As key components of multi-hazard, cascading slope-to-river systems around the world, landslide dams can have severe consequences. They form when landslides block a watercourse and can result in catastrophic flooding if they fail rapidly. Nonetheless, they are under-researched given the potentially high consequences of sudden dam breach and failure. Their formation, longevity, and breaching behaviour are not well understood, which is important information needed for effective risk management.

We present an Aotearoa New Zealand database of landslide dams, spanning pre-historic to historic natural dams compiled from several existing datasets and inventories. The database includes ~1030 landslide dams, as well as information for each dam such as catchment properties, landslide and dam dimensions, dam type, and dam stability where available. Where possible, quantitative attributes have been calculated automatically using arcpy (a Python site package that utilises ArcGIS processing tools), which allows consistency and repeatability in the database. A data quality ranking scheme has also been developed to assess the reliability of each dataset. The database will be available online on the OSF platform in mid-2023.

Several case studies, including the Hapuku, Stanton, Leader, Linton, and Conway landslide dams that formed during the 2016 Mw 7.8 Kaikōura earthquake, have been analysed in detail. Multiple field and remote sensing campaigns completed since 2016 – including field mapping, RTK surveying, drone photogrammetry, and LiDAR surveys – show the evolution of the landslide deposits and dams, providing high-resolution spatiotemporal data on their formation and breaching characteristics.

The database is currently being analysed to improve our understanding of dam formation potential and longevity, as well as breaching behaviour. These analyses will contribute to improved hazard management and avoidance.