Landslide Hazard Assessment of Oryahovo Area, Bulgaria

Abstract

The Oryahovo town is located at high Danube coast, and has been affected by landslide. Many houses and streets in the town are heavily deformed by continually ongoing landslide movements. The slope is affected by deep-seated landslide from translational type, which is in stabilized or in condition of slow creep. In the landslide body are created shallow landslides of rotation and flow type occur, which create the major problems of the town. In this regard, the conditions and factors of landslide activity have been analyzed. For this purpose, are composed three profiles for slope stability, located about 850 m apart. Current level of sustainability of the land is determined by applying the Janbu in “effective stress”. For the zoning of the landslide in Oriahovo were used the lowest values of the factor of safety along the three profiles. The calculations of slope stability in critical sectors of the town showed that the main factors of shallow landslides are groundwater fluctuation that is both of natural and/or man- made origin and the vibrations from heavy transport machines. An additional factor is seismic tremors that occurred from Vrancea seismic zone. The coefficient of stability decreases with 3 % from intensive traffic of heavy trucks through the town. On this basis, a Susceptibility hazard map of Oryahovo town has been compiled that represents the real situation of landslide hazard of the researched area. The map shows that the most endangered parts are the eastern ones and these above the ferry harbor of the town.