Automatic mapping subsidence caused by changes in the water table using remote sensing on the Island of Tenerife (Spain)

Abstract

The satellite Differential Interferometry Synthetic Aperture Radar provides subcentimetre-precision ground displacement in line of sight in large areas with thousands of points. The correct identification of small spatial phenomena is not easy amongst so much data. This paper deals with the application of the Getis-Ord Gi* statistic to the calculated vertical velocities for automatic subsidence mapping on the island of Tenerife between 2004 and 2010. By clustering values of high statistical significance (<0.01), amongst 55,225 calculated velocity points, previously identified cases of subsidence have been delimited in the northwest (Chio and Guimar). Other unexplored, more local sites with similar sink rates, were also detected to the east (El Rosario, -14mm/year) and west (Guía de Isora and Adeje, between -8mm/year and -20mm/year). Most of them are in small areas associated with groundwater extraction constructions and local agriculture where the water table had decreased drastically in previous years.