|Paper title||Monitoring landslides in critical infrastructures through Sentinel-1 DInSAR: the case of the Rules Reservoir (Southern Spain)|
|Form of presentation||Poster|
Unstable slopes in critical infrastructures such as reservoirs usually lead to risky situations that may imply a large amount of material, economic and even human losses. Remote Sensing techniques have proven to be very useful tools to avoid or minimize these disasters. One of these techniques is satellite radar interferometry (InSAR), which is capable of detecting millimetre movements of the ground at a high spatial and temporal resolution.
A significant improvement for InSAR is given by the recent C-band sensors on-board the Sentinel-1A and Sentinel-1B satellites. Sentinel-1 satellites have improved data acquisition and analysis, as their images are free-of-charge and offer wide area coverage at a high temporal resolution (sampling of 6 days) and high accuracy (up to 1 mm/year). But undeniably, other initiatives such as the European Space Agency (ESA)’s Geohazards Exploitation Platform (GEP) have entailed a meaningful advance for satellite Earth Observation (EO), especially for users with no capability to perform independent InSAR processing. GEP enables the exploitation of satellite images by providing several automatic InSAR processing services/thematic apps, mainly for geohazard monitoring and management. The Sentinel-1 CNR-IREA SBAS service is one of the GEP thematic apps that consist on a processing chain for the generation of Earth time series of displacement and mean velocity maps of displacement.
In this work, we made use of the CNR-IREA SBAS’s GEP service to perform InSAR analyses in one of the most critical infrastructures of Southern Spain: the Rules Reservoir. Therefore, we detected three active landslides within the slopes of the reservoir: the Lorenzo-1 Landslide, the Rules Viaduct Landslide and the El Arrecife Landslide. The first two are rotational landslides (the surface of rupture is curved) and they are affecting the N-323 National Road and the southern abutment of the Rules Viaduct (Highway A-44), respectively. The InSAR displacement rates are up to 2 cm/yr for the Lorenzo-1 Landslide and up to 2.5 cm/yr for the Rules Viaduct Landslide. Furthermore, the Time Series (TS) of accumulated displacement patterns of both landslides show a correlation with changes in the water level of the reservoir: the movement is accelerated with declines of the water level of the reservoir.
On the other hand, the El Arrecife Landslide has a translational character (the surface of rupture is planar) and therefore, it presents a potential hazard of experiencing a critical acceleration and a partial or total rupture of the slope. This would generate a collapse of a slide mass into the reservoir, what would have devastating consequences (for example, a massive flash flood downstream). InSAR was the technique that first revealed us the existence of this landslide, with a mean displacement rate of 2-2.5 cm/yr, being up to 6 cm/yr in the landslide's foot. Because of its potential hazard for the reservoir, we applied other techniques to further characterised the landslide: geological and geomorphological mapping, kinematic analysis for slope instability, volume estimation of the landslide, photogrammetry, and geophysical techniques (Ground Penetrating Radar). Through the latter one, we estimated a vertical movement of the landslide around 2 cm/yr, that is well-correlated with the rate obtained by InSAR. As the other landslides, the movement of the El Arrecife Landslide foot is accelerated with the reservoir water level declines.
With the data presented, we provide a first view of the nature and displacement of these landslides, as well as the hazard that they imply to the Rules Reservoir. Having done this, we consider essential to keep monitoring the landslides through InSAR and other in-situ monitoring techniques. In such way, possible pre-failure precursors of a rapid acceleration could be identified far enough in advance to avoid irreversible damages in the reservoir and related infrastructures. A continuous monitoring of the landslides is the key to conduct to a suitable and safe management of the reservoir, especially for water discharges.
This work has been developed in the framework of the RISKCOAST project (SOE3/P4/E0868), financed by the Interreg Sudoe Program (3rd call of proposals) of the European Regional Development Fund (ERDF).