Potential cascading geohazard: El Arrecife landslide in Rules reservoir, Southeastern Spain

Abstract

A multidisciplinary study integrating geological, geomorphological, geophysical, geotechnical, and numerical modeling has been implemented to assess the potential cascading geohazard of the El Arrecife landslide. It is an active landslide, located in the tectonically active central Betic Cordillera (southern Spain), posing a threat to the Rules reservoir, and to the N-323 and A-346 roads, and the A-44 highway, connecting the city of Granada to the coast. This study redefines its morphology and characterizes its stratigraphy for the first time. A continuous rupture surface has been identified, with an estimated total volume of approximately 8 × 106 m3 of highly weathered phyllites overlying a heterogeneous metamorphic basement. The landslide is composite, with a 1 km long head comprising two main bodies of similar size (500 m long and 400 m wide each) and ductile deformation features. It has been further enlarged and accelerated by anthropogenic intervention. Stability modeling indicates that the rapid disengagement of the entire landslide may be triggered by a Mw 6.0–6.6 earthquake originating in the nearby Padul–Nigüelas, Dílar or Albuñuelas faults at the upper end of their seismic potential. The simulation of the impulse wave generated in the Rules reservoir predicts a maximum height of 46 m on the opposite shore, when the reservoir is at its full capacity, sufficient to reach and locally flood the A‑44 highway, and slightly overtop the dam. This study emphasizes the need for enhanced monitoring to anticipate and mitigate its potential cascading geohazard around the Rules reservoir and in worldwide analogues.