The landslides in Bulgaria — factors and distribution

Abstract

The necessity of contemporary assessment of the natural hazardous processes on the territory of Bulgaria leading to disastrous and catastrophic situations in a number of regions is motivated by their high activity resulting in destruction of building fund, infrastructure, historicalmonuments, land use disturbance and annihilation of areas, interrupting of communications, aggravation of ecological conditions, human health threats, social stress enhancement. The landslide manifestations displayed recently along the Black Sea coast and the Danubian riparian area, the Rhodopes and other parts of the country and their serious consequences confirm the long ago ascertained truth that the Bulgarian territory is characterized by a high degree of landslide hazard. The geological-tectonic conditions and the relief of the country determine the development of a large number of landslides on its territory. The many years of research and applied activities on landslides have led to the establishment of important relationships for their distribution, factors for origin and activation, mechanism and dynamics, etc. The origin and activation of landslides is a consequence of the influence of many factors — tectonic, seismic, geomorphologic, climatic and technogenic ones. A part of them act permanently, while others have short-term impact. Both separately and in combination they reduce slope stability and provoke the manifestation of big and destructive landslides. The impact of the destabilizing factors and the distribution of 403 landslides are analyzed in this work. Regions with different degree of landslide hazard have been distinguished. Diagrams are shown for the regional distribution and time of landslide display. The weighted effect of the destabilizing factors for slope stability formation is different. A part of them as the contemporary vertical movements and earthquakes are of regional importance, others act locally — erosion, abrasion, precipitation. The origin of the active landslides may be closely related to contemporary tectonic activity. The regional distribution of the landslides according to their volume shows that landslides with a volume up to 10 million m3 are the prevailing type in the country. The most numerous landslides in this group — about 50% of the total number — are observed along high Danubean Bank and Northern Black Sea coast, in the tectonically active grabens as Sofia, Pernik or Simitli and the landslides along some of the faults in the Strouma zone. The largest landslides with a volume of more than 100 million m3 are encountered along the Danubean Bank, the Northern Black Sea coast and in Rhodope Region.

Methods used for monitoring geodynamic processes on the territory of Bulgaria

“…Geodetic, inclinometric and other studies are successfully applied to specially constructed polygons. Regardless of the value of the data obtained, the number of sites studied is small to be representative of the vast number of landslides of various types spread throughout the country (Berov et al, 2002;Bruchev et al, 2007;Ivanov et al, 2022). In the last few years, in-depth monitoring studies have also been carried out on terrains affected by rockfall processes.…”

Earthquake-induced landslide hazard assessment in the Vrancea Seismic Region (Eastern Carpathians, Romania): Constraints and perspectives

“…All these processes have been attributed to the 1977 earthquake. According to Bruchev et al, (2007), the same seismic event has caused the initiation of several landslide failures along the Bulgarian bank of the Danube (160-250 km) and the northern part of the Bulgarian Black Sea coast (250 km), a region recognized as being prone to landslides such as falls and bank collapses (Berov et al, 2016). Possible long-distance impact of the 1977 and 1986 earthquakes was mentioned for the Polish Western Carpathians (650-700 km) by Wistuba et al, (2018).…”

Influence of geological and hydrogeological settings in assessing the stability of a landslide slope in the Tutrakan area, Northeastern Bulgaria

“…Тутракан са регистрирани 13 броя съвременни, стари и древни свлачища ("Геозащита" ЕООД, клон Плевен, МРРБ). Част от тях са стабилизирани, други са с периодични активизации, а трети са с потенциална опасност от възникване на свлачищни процеси (Berov et al, 2002(Berov et al, , 2020Bruchev et al, 2007;Evlogiev et al, 2010;Ivanov et al, 2017Ivanov et al, , 2022. Те са разположени между първата и четвъртата надзаливни тераси на р. Дунав.…”