Dynamics of a Mass Movement Triggered by Heavy Rainfall: A Case Study from the Black Sea Region of Northern Turkey

Abstract

Following a period of heavy precipitation, a large and complex mass movement, namely the Şerefiye landslide, occurred in the Black Sea region of northern Turkey on 23 June 2000. This paper describes the conditioning factors of the landslide and interprets the mass transport processes. Geology, geomorphology and tectonics were considered as the conditioning factors of the failure. Observations showed that the sloping (c.9°) area is not covered by forest trees at the crown where the motion initiated. Analysis of the hydrological response of slopes during the rainstorm indicated that the majority of the failures were caused by the development of a perched water table in the thin surface layer of clay origin, due to infiltration during heavy rain. The distance from the crown down to the toe of the landslide was measured at more than 50 m. The landslide has block sliding characteristics in the upper portions and a debris flow/soil flow component around the margins of the sliding blocks in the middle parts and at the toe. The movement was initiated near the crown as a result of the excess water content between the main formation and the clay at the end of three days of heavy rainfall. The early perturbations lasted for five to six hours, after which the central part of the zone started to move as a soil flow, in which very large intact blocks were transported. Even though the movement was very rapid (1.2 m/min), there was no loss of life. However, the movement closed the road link between Sinop and Ayancik. © 2004 Taylor and Francis.