SLOWMOVE – A numerical model for the propagation of slow-moving landslides: a 1D approach and its application to the analysis of the Valoria landslide (Apennines, Italy)

Understanding the behavior of landslides often starts with a numerical simulation that accurately accounts for observed physical processes. This research proposes a method for the implementation of the dynamic SLOWMOVE model to a high-mobility, moderate velocity earth flow located in the northern Apennines. The Valoria landslide is 3.5 km long earth slide- earth flow that resumed activity in 2001. Landslide materials comprised of disaggregated Flysch, Marl and Claystones are mainly transported as earth slides in the upper slope, and as earth flows in the main track. Repeated acceleration events lasting several weeks occur seasonally since 2001 reactivation. During events it can reach velocities of about 10 m per hour with a cumulative displacement of hundreds of meters. Through this intermittent activity, more than ten million cubic meters have been transferred down-slope since 2001, changing significantly and several times the morphology of the slope

Applications of a numerical model for slow moving landslides to the Valoria landslide in the Italian Apennines, and the Super Sauze mudslide in the French Alps

ISBN 2-95183317-1-5This research demonstrates the applicationof the dynamic SLOWMOVE model onthe Valoria case study located in the northern Apennines (Italy) and the Super-Sauze landslide in the southwestern Alps (France). The SLOWMOVE model is based on the Navier-Stokes equations. The landslide is modeled as a one-phase material with homogeneous and constant rheological properties. The slow movements of landlside materials allow for the cancellation of the inertia term from the momentum equation. At the Valoria case study site a 3.5 km long earth slide/flow with materials comprised of disaggregated Flysch, Marl and Clay-stones resumed activity in 2001 after a suspended phase. The landslide is characterized as earth slides in the upper slope, and as earth flows in the main track following complete disaggregation of the materials in the source areas. During reactivations, the earth flows can reach velocities up to 10 m·h-1. Characteristic for the landslide activity are repeated acceleration events ascribed to seasonal climatic inputs. Through continuous activity since 2001, more than 15 million cubic meters of material have been transferred down-slope. The Su-per-Sauze landslide is triggered in Callovo-Oxfordian black marls and is composed of a silty-sand matrix mixed with moraine debris. It extends over a horizontal distance of 850 m with an average slope of 25° impli-cating a volume of 560,000 m³. The complex paleo-topography covered by the landslide is made by succes-sions of crests and gullies which play an essential role in the mudslide behavior by creating sections with dis-tinct kinematical, mechanical and hydrological characteristics. The mudslide kinematics is characterized by a spatially heterogeneous displacement field with velocities ranging from 0.01 to 0.40 m day-1. For the Valoria landslide, the performance of the 1D approach of SLOWMOVE was analyzed on a representative landslide cross-section from the main track zone down to the toe zone. Multi-temporal Lidar surveys in conjunction with a large set of surface displacement data obtained from continuous monitoring since March 2008 was used to calibrate and evaluate the SLOWMOVE model. The model is capable to simulate realistic velocities and displacements but failed to achieve an accurate topographic reconstruction of the morphologic changes between 2003 and 2007. For the Super Sauze mudslide, the 2.5 D approach is used to simulate the heteroge-neous displacement field of the mudslide. The performance of the model is evaluated on multi-temporal and spatially distributed datasets of landslide displacements for the period of summer 200