Twenty-year advanced DInSAR analysis of severe land subsidence: The Alto Guadalentín Basin (Spain) case study

• Published in: Engineering geology 2015-11, Vol.198, p.40-52
• Main Authors: Bonì, Roberta, Herrera, Gerardo, Meisina, Claudia, Notti, Davide, Béjar-Pizarro, Marta, Zucca, Francesco, González, Pablo J., Palano, Mimmo, Tomás, Roberto, Fernández, José, Fernández-Merodo, José Antonio, Mulas, Joaquín, Aragón, Ramón, Guardiola-Albert, Carolina, Mora, Oscar
• Format: Article
• Language: English
• Subjects: ALOS (satellite); Basins; Global Positioning System; GPS; Ground surface displacement; Groundwater level; Land; Land subsidence; Lorca; Persistent Scatterer Interferometry (PSI); Satellite imagery; Spatio-temporal analysis; Subsidence; Synthetic aperture radar
• ISSN: 0013-7952; 1872-6917
• DOI: 10.1016/j.enggeo.2015.08.014

A twenty-year period of severe land subsidence evolution in the Alto Guadalentín Basin (southeast Spain) is monitored using multi-sensor SAR images, processed by advanced differential interferometric synthetic aperture radar (DInSAR) techniques. The SAR images used in this study consist of four datasets acquired by ERS-1/2, ENVISAT, ALOS and COSMO-SkyMed satellites between 1992 and 2012. The integration of ground surface displacement maps retrieved for different time periods allows us to quantify up to 2.50m of cumulated displacements that occurred between 1992 and 2012 in the Alto Guadalentín Basin. DInSAR results were locally compared with global positioning system (GPS) data available for two continuous stations located in the study area, demonstrating the high consistency of local vertical motion measurements between the two different surveying techniques. An average absolute error of 4.6±4mm for the ALOS data and of 4.8±3.5mm for the COSMO-SkyMed data confirmed the reliability of the analysis. The spatial analysis of DInSAR ground surface displacement reveals a direct correlation with the thickness of the compressible alluvial deposits. Detected ground subsidence in the past 20years is most likely a consequence of a 100–200m groundwater level drop that has persisted since the 1970s due to the overexploitation of the Alto Guadalentín aquifer system. The negative gradient of the pore pressure is responsible for the extremely slow consolidation of a very thick (>100m) layer of fine-grained silt and clay layers with low vertical hydraulic permeability (approximately 50mm/h) wherein the maximum settlement has still not been reached. •A 20-year period of subsidence evolution is monitored using multi sensor SAR images•The maximum cumulative subsidence in 20-years period reaches 250cm•DInSAR surface displacements provide locally comparable results with measurements acquired by two permanent GPS stations located in the study area•The subsidence is correlated with the thickness of the compressible deposits•The subsidence is not correlated with piezometric level due to delayed consolidation