Special Section on Landslides: Setting the Scene and Outline of Contributing Studies

Abstract

Landslides generally impose a considerable threat to human life, infrastructure, and the environment, especially in alpine areas. Landslides belong to the phenomena of mass movements, such as rock falls, avalanches, and debris fl ows. Although landslides and debris fl ows have much in common at fi rst sight, they diff er strongly with respect to underlying physical processes, as elaborated in Armanini and Michiue (1997) and Wang et al. (2004Wang et al. ( , 2007.Landslides are categorized as shallow or deep seated. Shallow landslides have a vertical extent up to a few meters and horizontal extent up to a few hundred square meters. Formation of shallow landslides mostly occurs in response to extreme rainfall events (Terlien, 1998; Delmonaco and Margottini, 2004) and depends on near surface structures and processes. Understanding and predicting shallow landslides is a more straight forward exercise, when compared to deep seated landslides, although it is by no means simple. Deep seated landslides have a vertical extent up to several tens of meters and spread horizontally from a hundred to a few thousand square meters. Th ey are distinguished into fast moving and creeping landslides. Fast moving, or active, landslides, such as the "Super-Sauze" in the French Alps (Malet et al., 2003), exhibit movement rates of up to tens of meters per year. Creeping landsides move several centimeters or decimeters per year; a prominent example is Sibratsgfäll/Rindberg in Vorarberg Austria (Jaritz et al., 2008). Understanding the cause-and-eff ect relationships of deep seated landslides is much less straight forward than those of shallow landslides because: (i) they are controlled by multiple structures that in turn aff ect multiscale interactions and feedbacks between hydrologic, geohydraulic, and soil mechanical processes, and (ii) both short-and long-term triggers aff ect soil deformation, shear band formation, and thus movement of the creeping hillslope body. Short-term triggers are heavy rainfall events, vadose zone and groundwater fl ows, and pressure dynamics, but they can also include river bank or hillfoot erosion during fl ood events, depending on site conditions. Long-term triggers include seasonal changes of the self-load, due to seasonal soil moisture variations and snow cover, and the contribution of trees and infrastructure to the self-load.Although creeping, deep seated landslides appear less spectacular than the active landslides, they cause steadily increasing damage to buildings and infrastructure in the long term. Creeping landslides can furthermore be regarded as the ideal and "safe" environment to learn:• Whether and how do most recent measurement technology and experimental design allow assessment of information on dominating structures, processes, and their feedbacks that is suffi cient for understanding how fl ow and creeping deformation processes within large and heterogeneous systems respond to the abovementioned short-term and long-term triggers?• Whether and how can we develop and implement a coupled mod...

Upscaling the shallow water model with a novel roughness formulation

“…The incorporation of these effects into the shallow water equations can be found in, e.g. Hinkelmann (2005).…”

“…Extensive numerical simulations of surface and subsurface runoff for this domain were carried out in Simons et al (2014), Stadler et al (2012) within Research Unit 'Coupling of flow and deformation processes for modelling the movement of natural slopes' funded by the German Research Foundation (Hinkelmann et al 2011). During these simulations, the model was calibrated with a runoff coefficient W ¼ 0:3 in combination with a linear reservoir model to account for the slower discharge component in the subsurface, which was identified as a crucial contributor to the discharge at the outlet of the domain.…”

Connected flow paths as first order control on critical zone water flows: coincidence or self-organized optimality?

“…Evaporation is however strongly reduced during rainfall events and evaporation fluxes are two orders of magnitude slower than rainfall intensities that can reach up to tens of mm h −1 . If rainfall did accumulate only at the land surface and in the top soil this would imply fast rising potential energy gradients, high mechanical loads and a reduced shear stability of the soil (Lindenmaier et al, 2005;Wienhofer et al, 2011;Hinkelmann et al, 2011;. Depletion of these large gradients and mechanical stressors is only possible by means of fast mass flows that redistribute water in soil and export "excess water" from the system.…”

Soil Moisture Assessment over an Alpine Hillslope with Significant Soil Heterogeneity

“…Information about soil water content and its temporal dynamics is fundamentally required to understand or predict various processes related to human welfare going on in the near‐surface underground, for example, groundwater recharge, soil chemical processes, or vegetation development. Furthermore, soil water distribution and variation, for example, in response to heavy rainfalls or snow melt, may trigger hazardous mass movements in mountainous regions, that is, in the form of shallow landslides or debris flows (e.g., Delmonaco and Margottini, 2004; Hinkelmann et al, 2011). Thus, a wide variety of geoscientific or related disciplines have been interested in assessment of soil water content in near‐surface porous media.…”