Thom A. Bogaard

 ABSTRACT

The management of landslide risk and, more generally, natural risks is an essentially interdisciplinary task, as the contribution of many knowledge fields is required. In fact, a modern approach to landslide risk management involves the deployment of a layered strategy, including not only structural measures such as building defense structures or slope stabilization works, but also non-structural measures which require setting up on-site monitoring networks, remote sensing monitoring schemes, fast and reliable transmission of data and its quality control, development of models and decision support tools to assess the risk in real-time.

Rainfall-induced landslides is an interdisciplinary topic that requires knowledge from geomechanics, geomorphology, hydraulics and hydrology fields, to name a few. More specifically, the representation of hydrological processes in the models used for assessing the stability of slopes is often incomplete. Landslide hydrology, however, is not simply putting together hydrological calculations (modeling) with the knowledge coming from the above mentioned disciplines. In fact, the main challenge is embedding our increased understanding of hydrological processes in hillslopes and catchments in a physically correct but also parsimonious manner for landslide hazard assessment. The focus hereto, should be on inclusion of the non-linear behavior of hydrological response on precipitation due to complex water storage in soil layers as well as in the entire catchment. This boils down to an issue in matching processes occurring at very different time and space scales. Special attention should be given to the boundary conditions around the domain considered for slope stability analysis.

The small scale hydrological processes (e.g., infiltration and snowmelt) directly affect the stress state of soil (at pore scale), leading to landslide trigger. The catchment scale processes create the preconditions for the trigger to take place, so they are landslide causes but in our modelling domain often only visible as boundary condition. Uniquely and interestingly, the hillslope scale hydrological processes, developing in the same domain considered for slope stability assessment, make causes and triggers meet. Therefore, past and current research on landslide hydrology can be usefully regarded into this cause/large scale and trigger/small scale concept.

The lecture will address the work done in the field of landslide hydrology and shed light to important knowledge gaps that urgently need to be addressed in order to arrive at improved landslide mitigation and early warning systems.