Actividad historica y caracteristicas de los movimientos de ladera de rosiana Gran Canaria

Abstract

The Rosiana landslide of 1956 (Gran Canaria) is the largest historic movement known in Canary Islands. It is located at the bottom of the Tirajana Depression. This is a complex site where many old landslides are present and it has been studied recently (Lomoschitz, 1995). From historical information, field work and the analysis of the movement we conclude that it is a translational earth slide, that has been reactivated five times in historical dates. From back-analysis a friction angle (Φ′) of 17′7 - 21′6° and cohesion (c′) cero has been estimated. Rainfall analysis shows that intense and con-tinuous precipitation periods (more than 400 mm. acumulate rainfall) are needed to reactivate the landslide. On the other hand, a return period upper than 100 years has been calculated from the maximum rainfall intensity in 24 hours.