Improving the quality of landslide events recorded in the Norwegian database

The national database of mass movements includes more than 90000 landslide and snow avalanche events from the year 900 up to present. The main processes registered are landslides, snow avalanches, slushflows, ice falls and submarine landslides. The Norwegian Water Resources and Energy Directorate (NVE) has run the database since 2014 and can be accessed at www.skredregistrering.no and downloaded NVE - Nedlasting av kartdata

Some of the recorded landslides, like debris avalanches, debris flows, and shallow soil slides have been used to define landslide thresholds and create a landslide index that is used in the operational landslide forecasting and warning service. The poor quality of landslides registered in the database (uncertainty about landslide type, date and time and location) has limited the further analyses of thresholds and delayed the automatic updating of landslide thresholds. Controlled data could not be sent into the database; therefore, a new download of data and new control is necessary every time thresholds are to be updated. Could it be possible to give a quality score to each landslide, so it will be easy to automatically download data into threshold analyses, instead of a manual selection? Could it possible to perform the control directly into the database, to avoid a new control? 

In recent years, procedures for quality control of historical landslides have been proposed at NVE, initially for weather-induced landslides, but later extended to other landslide types, like rock avalanches and clay slides, quick clay slides and slushflows. The quality control activity has been implemented more systematically since 2018 using all sources of information available: newspapers, aerial photos, technical reports. Four quality levels have been proposed, and quality criteria have been described. In this work it is presented how the quality control process is organized, which quality criteria are in use for the different landslide types, and which lessons we have learned.

The systematic quality control process is providing spatially and temporally improved dataset to be used not only in landslide threshold analyses, but also to be used in hazard mapping and the calibration of landslide models that simulate initiation areas and runout, used for susceptibility and hazard maps, as well as in other research projects. The control process has contributed to a better description and mapping of certain landslide types (like debris flows and debris avalanches, clay slides) and slushflows, and improved the overall registration and controlling tools.