cudam
cudam
Line 1 - Hill slope hydrology and the formation of solid runoff
Responsable Riccardo Rigon

Aims and goals

  • To model the mechanisms of infiltration and water transfer along the Alpine slopes and alluvial cones by means of high resolution digital terrain maps, satellite data, field measures, and new-concept geomorphologic and hydraulic models of the hydrological cycle.
  • To identify the zones of possible basin-scale landslide triggering, the volumes transported, and the critical events.
  • To improve the procedures for digital terrain model reconstruction and land use classification, on the basis of remotely sensed data.
  • To define simplified support procedures for the planning of soil defence structures and works.

Project Description

As opposed to what happens in the lowlands, the hydrogeological risk in mountain basins is due to the contribution of both solid and liquid discharges. It is not possible to tackle these two components separately.

For the analysis of the consequent danger and risk in mountain basins a multitude of methods have been implemented over the years, principally based on statistical analyses of the relationship between sediment volume and precipitation or on the creation of a check-list (Aulitzky, 1980; Kronfellner-Kraus, 1985; Meunier, 1991; Rickenmann, 1997). Methods based on a more physical and geomechanical modelling of the phenomena have been implemented at the University of Kyoto by Prof. Takahashi's research group, however, considerable simplifications were introduced in the stratographic and geological structure of the sediment deposits. Particularly, the problem of the hydrological boundary condition was ignored in its entirety.

A distributed model of shallow landslides on basin-scale, called SHALSTAB, that fully uses information derived from digital terrain models and, potentially, from digital data from laser instrumentation or of comparable definition, has been recently implemented by Dietrich et al. (1992, 1995). The model considers the topographical analysis in a duly simplified synthesis of the hydrological processes of subsurface flow and the slope stability model derived from an infinite slope.

These studies of the University of Berkeley constitute the starting point for the current line of research that proposes, among other goals described later, to build an equally simple model of the instability generated by surface runoff (of primary importance to this purpose are the studies of Iverson, 2000), and to better characterize the effects which derive from the presence or absence of vegetation and different geolithological typologies.

From a practical point of view, the current line of research proposes to obtain models that serve to identify the danger zones on basin-scale; to determine their extension and the mass which is initially moveable (which represents the triggering of the phenomenon but not the dynamic evolution of the flow or the erosion). Furthermore, it is desirable to contribute to the identification of the events which can generate landslide phenomena (as a function of the variable water content of the soil before the event and the amount of soil present).

The problem of flow generation, or of the partitioning of the flows into superficial and sub-superficial flows (and the complementary problem of determining the water content of the soil), is the main hydrological problem studied. As well as simplified models, the project also proposes to develop and validate the GEOTOP distributed hydrological model. This model allows the accurate study of the dynamics of pore water pressure in the soil, so extending and completing the studies of Hsu (1994), Wu and Sidle (1995), and Duan (1996). In fact, recent studies suggest that variations of pore water pressure along a slope propagate much more quickly then movement of the water itself (Torres, et al., 1998, Reid et al 1997), even though the heterogeneity of natural mediums and soil cover normally make any accurate prediction based on purely deterministic tools extremely difficult (Johnson and Sitar, 1990).

Of course, the hydro-meteorological aspects of the problem are not neglected. Of particular interest is the possibility of linking both the conceptual models and the distributed hydrological models to precipitation forecasting and observation and so improve, for example, the results already obtained by Walko et al. (2000).

Within the framework of this research project, the use of unconventional measuring instruments and techniques (at least in the operational sense) covers an important role. Of particular importance are the various techniques of satellite surveying by means of acquisition and analysis of images, even in multitemporal sequence, and the use of extremely high-resolution digital terrain models (like those obtained with airborne altimetric lasers or the latest generation of orthophotogrammetric techniques).

Subproject

Remote sensing data and GPS 

  • Topographical analysis by means of the acquisition of high-resolution digital terrain data
  • Remote sensing and classification of soil cover
  • Dendrochronological analysis
  • Coordinated representation of data with "Open Source" Geographical Information Systems (GIS)
  • Change Detection (SAR - R.Genevois, University of Padua)

Theoretical Studies of Geomorphology, and Erosive and Landslide Processes 

  • Analysis of the slope-area-curvature relationships
  • Analysis of the production and action of surface runoff
  • Characterization of soil depth
  • Determination of particular solutions of Richards' equation at basin scale and the determination of the events that trigger landslides

Distributed Numerical Modelling of the Hydrological Cycle at Basin Scale 

  • GEOTOP
  • Coupling with a limited scale, non-hydrostatic, meteorological model
  • Study of the effects of vegetation and the vegetative cycle on the hydrological cycle
  • Application of the research work to some experimental hydrographic basins

Application of the Research Work to Some Experimental Hydrographic Basins