SLIDELAWS

Constraining Geomorphic transport laws for mass wasting processes

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 Obiettivo del progetto (Objective)

'Today LiDAR technology gives us the opportunity to detail geomorphic features like landslide scars, and first-order streams at the decimetre scale, so that we can characterize process-specific dynamics over large landscape areas for the first time. The ability to identify and measure such features might allow us to quantify colluvial sediment flux and to forecast landslide hazards more accurately. In this context, the ability to partition the landscape into process domains by connecting landscape form to process enables us to rapidly assess hazards at new field sites. This connection between process and form has been cast into the framework of geomorphic transport laws, which can be used to estimate both position, and transport rates of Earth surface processes. Currently, geomorphic transport laws are only available for a handful of processes and none have been developed for landslides and debris flows. These are most needed for addressing fundamental scientific issues (i.e., long-term landscape evolution), and for solving more practical problems (i.e., hazard assessment). We propose to advance the current understanding of hillslope processes at the watershed scale by constraining transport laws for mass wasting in the Trentino Region using LiDAR, field methods, and GIS distributed modelling. Specifically, we aim to express landslide sediment flux as a function of hydro-geo-topographic attributes across terrain units. Objectives include to: (i) Classify this landscape into geomorphic process domains; (ii) Discriminate the topographic signatures of post-glacial mass-wasting processes that are superimposed to the glacial palimpsest; (iii) Document the variability of the saturated and unsaturated hydraulic properties across bedrock and surficial units; and (iv) Investigate the effects of hillslope hydrology, as reflected in the hydraulic properties, of both bedrock and surficial units on mass wasting style in terms of magnitude-frequency relations and sediment flux.'

Introduzione (Teaser)

Erosion, landslides and changing topographies can have a strong impact on rural areas, agriculture and development. A combined technique can help map the frequency and locality of these geomorphic changes.

Descrizione progetto (Article)

The varying cliffs, valleys, tilting plains and mountains of the Earth are known as hillslopes; here, large quantities of soil and sediments have been in constant motion over thousands of years. This movement process is called mass wasting and determines if the land is suitable for agriculture, building or other activity.

The EU-funded 'Constraining geomorphic transport laws for mass wasting processes' (Slidelaws) project is investigating the concept of mass wasting. It is studying two drainage basins of the Trentino Region in the central Italian Alps, those of Val di Sole and Val di Fiemme.

The project is examining the formerly glaciated landscape, including its hydro-geomorphology, bedrock, sediment flux and other characteristics that impact mass wasting. This is being achieved through a series of aerial photographs taken from 1954 to 2006, optical remote sensing technology (light detection and ranging or LiDAR), and laboratory experiments. The monitoring techniques have exposed the landslide characteristics of the regions and revealed how this land is used (e.g. alpine, pasture or forest), as well as topographic attributes (i.e. elevation and slope).

When combined, these techniques are effective in understanding the frequency of landslides and their possible threats on settlement and agriculture, among others. To illustrate, the rate of landslide occurrence per unit area has helped calculate the intensity of the landsliding process.

Another result from the Slidelaws project has highlighted clear lithologic and tectonic controls. High magnitude-low frequency events occur exclusively on metamorphic rocks. Events smaller than 300 000 m2 occur mostly on metamorphic slopes whereas sedimentary and intrusive lithologies are substantially less active. Again, this information can improve prediction and localisation of landslides.

On the whole, this project is helping to advance our knowledge of landslide occurrence and outlining geomorphic transport laws. By identifying peculiarities in the geomorphology, slope characteristics and water flows, it will be possible to estimate the extent of potential landslides, including risk to infrastructures and residential areas.