Human-induced coastal landslide reactivation. Monitoring by PSInSAR techniques and urban damage survey (SE Spain)

In the present work, we show the case of Marina del Este resort, located in the southern Mediterranean coast of Spain (Costa 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 following: (1) geomorphological analysis, (2) PSInSAR technique application (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 widespread damages in the resort. Buildings with high degree of damage 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.