Landslides (2015) 12:1007–1014 DOI 10.1007/s10346-015-0612-3 Received: 2 March 2015 Accepted: 13 July 2015 Published online: 28 July 2015 © Springer-Verlag Berlin Heidelberg 2015 Davide Notti I Jorge Pedro Galve I Rosa María Mateos I Oriol Monserrat I Francisco Lamas-Fernández I Francisca Fernández-Chacón I Francisco Javier Roldán-García I José Vicente Pérez-Peña I Michele Crosetto I José Miguel Azañón Human-induced coastal landslide reactivation. Monitoring by PSInSAR techniques and urban damage survey (SE Spain) Abstract In the present work, we show the case of Marina del Este resort, located in the southern Mediterranean coast of Spain (Cos- ta del Sol). A medium-scale landslide has been recognized when the area was virgin. In 1977 started the initial works for urbanizing the area; later, buildings and facilities expanded uphill covering the landslide body. This case is characterized by a long history of corrective drainage and mitigate measures without success. An analysis of the landslide activity has been carried out by applying different approaches and based on the combination of the follow- ing: (1) geomorphological analysis, (2) PSInSAR technique appli- cation (ENVISAT 2003–2009), (3) an assessment of building and infrastructure damages, (4) rainfall time series analysis and (5) ground monitoring (2010–2011) data interpretation. Results show that, from 2003 to 2009, the landslide was active with velocities ranging from 5 to 15 mm/year. During the exceptional rainy period in winter 2009–2010, the movement velocity increased about ten times (velocities ranging from 40 to 90 mm/year) causing wide- spread damages in the resort. Buildings with high degree of dam- age are located at the toe of the landslide, close to the marina, where some dwellings have been evacuated. Marina del Este is a good example to show that landslides on coastal and steep slope areas are very vulnerable to reactivations and require thorough studies before any anthropic modification. Keywords Landslide . Reactivation . Urban development . PSInSAR . Damage . Mediterranean coast Introduction The rapid urban development occurred along the Mediterranean coast in Spain during the past 20 years increased the areas poten- tially affected by natural hazards and, in particular, landslides (Olcina Cantos 2009). New urban areas were extended onto large dormant landslide zones, as they generally present a more gentle slope than adjacent stable zones and thus is assessed as more favourable for settlements (Cascini et al. 2005). Pre-existing land- slides, with basal shear zones in the residual strength condition, can be easily reactivated in coastal areas, as the erosive action of the sea is a continuous destabilizing factor. Additionally, if the loading and morphological conditions of the slope are changed, problems use to appear straight away. Two excellent examples of this scenario can be found in the residential resorts named BCármenes del Mar^ and BMarina del Este^, located close to the popular holiday villages of La Herradura and Almuñécar (Costa del Sol, Spain). Both urban areas are affected by slow movements due to landslide reactivations which have caused severe damage to dwellings and holiday apartment blocks. This paper is focused on the Marina del Este resort located in the eastern side of Punta de la Mona Promontory (Fig. 1) in the municipality of Almuñécar (Granada). A medium-scale landslide was identified when the area was completely virgin, using the 1957 aerial photos. In 1977, the urban development started with the construction of a marina at the toe of the slope. Later, residential development spreads into landslide-prone terrain covering the orig- inal landslide body. During the past 38 years, numerous interven- tions have been carried out in this resort in order to minimize and mitigate damages caused by the landslide reactivation and especially after the extreme rainfall period December 2009–March 2010. In the present work, history of interventions and damages is related to slope monitoring data and new space-based measure- ments obtained through the Persistent Scatterer Interferometry (PSI) approach described by Crosetto et al. (2011)). Synthetic Aperture Radar (SAR) images taken by ENVISAT during the period 2003–2009 were exploited. The development of advanced multi- temporal Differential SAR Interferometry (DInSAR) and, in par- ticular, the persistent scatterer (PSI) techniques (e.g. PSInSAR™ by Ferretti et al. 2001; SBAS by Berardino et al. 2002; SPN by Mora et al. 2003, CPT by Blanco-Sanchez et al. 2008; SqueeSAR by Ferretti et al. 2011, PSIG-Cousin PSs (CPSs) by Devanthéry et al. 2014) has demonstrated a high capacity to detect slow ground movements (Del Ventisette et al. 2013; Bru et al. 2013). In this regard, the movement associated to extremely and very slow landslides (Cruden and Varnes 1996) is one of the geological processes detectable by (PSI) techniques (e.g. Farina et al. 2006; Meisina et al. 2008; Herrera et al. 2011; Calò et al. 2014; Cigna et al. 2013; Lu et al. 2014; Wasowski and Bovenga 2014). Landslides affecting urban areas are especially suitable to be identified by DInSAR, since buildings serve as very good SAR reflectors and, at the same time, this make possible to compare damages on buildings with InSAR-derived displacement data (e.g. Ciampalini et al. 2014; Galve et al. 2014; Cigna et al. 2010; Bianchini et al. 2015). The study area Geological and geomorphological setting The Marina del Este resort is located on the eastern side of Punta de la Mona Promontory (Fig. 1) between the localities of La Herradura and Almuñécar (Granada, SE Spain). The residential resort is located over a steep coastal slope and offers the appeal of a marina with water sports and tourist facilities. The buildings are generally terraced houses of two to three floors used for holiday residential purposes. Some facilities such as swimming pools, gardens and paddle courts were also built. During summer, a population around 2000 people live in the resort, being practically unoccupied during winter season. From a geological point of view (Fig. 1), the rocks of this promontory are traditionally assigned to the Alpujarride Complex Landslides 12 & (2015) 1007 Technical Note