Modelling of mobility of Rissa landslide and following tsunami

Landslides in sensitive clays pose a major threat to life, property and the environment. The lack of warning signs and the extreme mobility of quick clays increase the risk. When occurring along fjords, lakes or large rivers, the landslides can generate destructive tsunamis. Historical records show that 45% of the shoreline landslides in marine sediments in Norway triggered tsunamis with run-up height of 1 to 15 m. To improve the management of the hazard and risk due to landslides in sensitive materials, the profession needs to develop tools for modelling the mobility of landslides and their tsunamigenic potential. The paper back-calculates the 1978 Rissa landslide, one of the largest quick clay landslides in Norway. Because of the quantity of data available, the Rissa landslide provides a unique benchmark to study the mobility of the quick clay, and the tsunami following the landslide. The paper describes a new approach to model landslide mobility and tsunami run-up, and presents the results of the analyses and a comparison of the results with the observations. The back-calculated mobility (runout distance, flow velocity and debris thickness) and wave run-up on the lakeshore agreed well with the measurements.

Automated summary

Landslides in sensitive clays can pose a major threat, especially when occurring along fjords, lakes, or rivers, as they can generate destructive tsunamis. Developing tools to model landslide mobility and tsunamigenic potential is crucial for improving hazard and risk management. The back-calculation of the 1978 Rissa landslide in Norway provides valuable insights into landslide mobility and tsunami run-up, with results showing good agreement with measurements.