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Monitoring of Unstable Slopes in the Italian Alps Using Satellite Radar - Results of the ESA/ESRIN DUP Alpslope Project

Klaus Belitz(1) and Johannes Zilger(1)

(1) Teledata GeoConsult GmbH-srl, Siemensstraße 19, 39100 Bolzano, Italy

Abstract

Key words Natural Hazards, Landslides, Monitoring, ERS, Envisat, Synthetic Aperture Radar, Differential Interferometry

The issue While unstable slopes in the Alps are a severe permanent threat for the human society and economy in the region, the mapping and analysis of the geologic risks in this area is of essential importance and a strong political issue. The complete urban and regional planning has to be based on an analysis and classification of the terrain in terms of risks, to prevent existing buildings and infrastructures from damage or loss. In areas of elevated geo-risks additional preventive measures have to be planned and realised. As short-term activity the safety of inhabitants and visitors has to be guaranteed by recognising potentially hazardous sudden events to initiate security measures timely in advance (closing of roads, evacuation of buildings) supported by appropriate monitoring systems.

The ‘Alpslope’ Project: Partners, Elements and Goals Main objective of the presented project ‘Alpslope’ within the framework of ESA funded DUP (Data User Programme) is to develop and demonstrate services for mapping and monitoring unstable slopes based on widest use of satellite remote sensing data and integration in Geographical Information Systems (GIS) in close co-operation with a selected key-user. The results in terms of feasibility of the service and its performance regarding accuracy, speed of delivery and costs and benefits of the service are analysed and presented in detail. The key user committed to the project is the Geologic Service (Geologischer Dienst, Servizio Geologico) of the Autonomous Province of South Tyrol, being the authority responsible for all geologic mapping tasks regarding geology, tectonics, and associated geo-risks. As an intermediate user, the Department of Earth Sciences of the University of Modena and Reggio Emilia is involved in the project. Expert know-how and extended experience in mapping of hydro-geological and geomorphologic hazards and risk assessment is provided.

The Methods: Earth Observation and Ground Based Techniques The main methodological element is the detailed detection and mapping of the spatial distribution of the unstable slopes induced hazards. Direct information on geometric surface changes and displacements is provided by Differential SAR Interferometric Processing (DInSAR) of ERS and ENVISAT data. In the terrestrial methods used so far permanent punctual measurements of the geometric surface changes via Differential GPS, laser theodolites and borehole instrumentation are carried out. The system presented in this paper and initiated by the project is capable to integrate ground measurements and spatially extending observations derived from remote sensing data.

The Test-sites The project is developed within two test-sites, Corvara and Nals in the Autonomous Province of South Tyrol in the Italian Alps, defined together with the key user. According observations of the Geologic Service, surface displacements up to 11 m in the period between spring and autumn already occurred with the Corvara landslide. The test-site near the village of Nals / Nalles in the Etsch-valley, lies half way between Meran and Bozen on the southern mountain slopes of the valley. The test-site is part of a long colluvial slope, extending below a steep wall of outcropping rocks from Meran-Marling / Merano-Marlengo in the Northwest to Eppan / Appiano near Bozen in the Southeast. A series of landslides and debris flow events has actually occurred since the year 2000, and implementation of appropriate measures is a pressing issue. Results of the two test-sites are presented and discussed in the paper.

The Perspective The presented project ‘Alpslope’ displays the status of development of earth observation techniques suited for addressing the issue of unstable slopes and emphasises on interacting with the involved key users and intermediate users, meeting their specific requirements and finally integrating developed mapping products and monitoring services in the users operational environment.

 

Full paper

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry