Rainfall Influence on Landslide Dynamics (Carpathian Flysch Area, Romania)

Abstract

This study brings forward two important aspects concerning landslides that have an important role in the contemporary morphogenesis of the hilly and mountainous areas in Romania. The first topic refers to the recurrence of the landslides reactivation. The existing works proved that the starting point and the recurrence of landslides are mainly connected with the climatic periodicity, especially with the pluviometric surplus. For the mountainous flysch area, the periods with surplus of precipitation were recorded between 1912-1913, 1941-1943, 1970-1972, 2000-2005. Recent field studies, during the last two periods, show (on the background of a natural vulnerability) an extension of the area affected by active landslides. The second aspect that was taken into account is connected with the implications of the meteoric water on the landslide dynamics. In order to emphasize this relationship, the analysis was based on the measurements of the rainfall regime, moisture of the slope deposits as well as the landslide dynamics made in two experimental catchments. In order to measure the landslides dynamics, repeated topographical and inclinometric measurements were taken. The research was carried out over two years so as to identify the influence of the precipitation on two types of superficial deposits affected by active landslides. The investigations helped us reach the conclusion that the daily precipitation influences the moisture of the slope deposits only up to a depth of 50-60 cm. Between the date when the rain occurs and that when the landslides are accelerated, there is a difference of 10-15 days according to the infiltration rate which depends on the grain size of the deposits and their degree of disintegration.