Monitoring Alpine Transportation Infrastructures using Space Techniques
Strozzi, Tazio1; Caduff, Rafael1; Wegnüller, Urs1; Wirnsberger, Harald2; Kühtreiber, Norbert2
1Gamma Remote Sensing, SWITZERLAND; 2Institute of Navigation (INAS), Graz University of Technology, AUSTRIA

Rockfalls and landslides are natural hazards of special relevance to mountainous areas with severe human and economic consequences. The densely inhabited Alps, with its large network of transport infrastructures, are particularly sensitive to these types of hazards. Railways and roads companies are responsible for a safe and reliable operation along their networks and are thus generally interested on a wide-area early- warning system providing probabilities and intensities of potential hazard endangering their infrastructure. In case of imminent danger of a sensible section of the network, terrestrial deformation monitoring will be started and measurements repeated over time. An early warning system is then necessary only in emergency situations.

Within the Integrated Applications Promotion (IAP) programme of the European Space Agency (ESA) we are aiming at providing a service to the Alpine transportation infrastructure operators that is based on the integration of the space techniques radar interferometry and GPS/GNSS. The information to be provided is ground motion, which can include motion of the transportation infrastructure (railway, roads), motion of rocks or terrain slopes above transportation infrastructure, and motion caused by tunnelling.

The final users to whom our proposed service is aiming for are the operators of the Alpine transportation infrastructure (railway companies, institutes representing the national roads, companies from the energy sector) and private geological offices that often complement the infrastructure companies in displacement monitoring services. Higher priorities of the engaged user's community are related to wide-area investigations of slope instabilities as input to regional hazard maps. In that sense the higher perspective for the envisaged integrated service is for satellite SAR interferometry. In a repeated monitoring concept on selected slopes of relevant hazard, our perspective is focused on satellite SAR interferometry based on very-high resolution images along with terrestrial radar interferometry and GPS/GNSS. Concerning ground deformation monitoring in near real time with terrestrial radar interferometry and GPS/GNSS, there is an opportunity to attain acceptance of the proposed integrated service in the case of an efficient, cost-effective and reliable service. The overall space system is highly complementary to state-of-art terrestrial methods which are also limited in terms of spatial coverage, accuracy, temporal resolution and costs.

One focus of the project will be the acceptance of the space technologies in the user's practices. Proof-of-concepts are therefore carefully designed to meet this goal. In this contribution to the ESA Living Planet Symposium we will present results related to:
(1) a large-scale survey along the Gotthard railway using ERS and ENVISAT SAR data of the time period 1992-2010 performed in order to identify sectors of the network endangered by large slow-moving deep-seated landslides;
(2) a large-scale survey over the Alptransit tunnel conducted with satellite SAR interferometry using ERS and ENVISAT SAR data of the time period 1992-2002 in order to detect large-scale consolidation associated with pore-pressure reduction in the rock mass arising from drainage associated with the drilling of the tunnel at about 700-1500 m depth beneath the topographical surface;
(3) a local monitoring of an hazardous area along the Gotthard railway using terrestrial radar interferometry and GPS/GNSS focused on the interaction between weather/climate and deformation rates of rock glaciers and their release of sediment in debris-flow channels, causing a potential secondary hazard on the infrastructure lines in the valley bottom.