| |
Buzău County (110 km north-east of Bucharest; almost 6100 km2 of which half is represented by mountains and hills) is situated in the heart of Vrancea Seismic Region, which includes the Curvature sector of the Southeast Romanian Carpathians and represents the most active seismic region in Romania. Considered to be the most active sub-crustal earthquake province of Europe, it represents a continental collision area, characterized by weak crustal but intense sub-crustal seismicity (80-160 km in depth), a domain in which three-to-four major events (Mw > 7) occur per century.
The north-western half of the County is formed out of Buzău Carpathians and Subcarpathians, while its south-eastern half corresponds to the Romanian Plain. The high sector outlines two regions with different morphology, morphometry and morphodynamic patterns. The interior is represented by the Carpathian Mountains, built on harder flysch deposits (Cretaceous and Palaeogene), while the exterior consists of the hills and depressions of the Subcarpathians, corresponding to the less cohesive and heterogeneous molasse formations (Mio-Pliocene). In addition to the favourable lithology and structure, the neotectonic parameters (uplift rates of 5 mm/year in the mountain sector and 3-4 m/year in the Subcarpathian hills) and seismic features make the area even more vulnerable to present-day slope processes.
The low-to-mid altitude Carpathians, up to 1,300-1,700 altitude, have a 500-800 m relative relief, 8-10 km/km2 drainage density and 30-45o slopes. The Subcarpathians, with heights of up to 900 m are featuring morphometrical traits conditioned by the loose molasse deposits (dominated by schistose marls and clays): a relative relief of up to 300-500 m, 3-8 km/km2 drainage density and slopes below 30-45o.
The climate is of a moderate temperate hill and low-to-medium mountain type, marked by the Carpathian orographic barrier and a high foehn frequency. The precipitation has a torrential character during the summer (frequently 80-100 l/m2 in 24 hours) and is often overlapping the snowmelt of late spring. The yearly amount ranges from 550 mm at the outer border of the Subcarpathians to 900-1000 mm in the highest mountains. Monthly values have a peak of 70-150 mm in June, dropping to 25-40 mm (the lowest values), in February and March. This is reflected in the mean slope denudation values of 4 - 5 t/ha/year in the mountains and over 13 t/ha/year in the Subcarpathian hills.
The favourable conditions of life, namely accessible relief, mild climate, the presence of salt deposits, the mountain-plain contact propitious to intense trade relations, has long allowed and encouraged the development of human activities. Presently, the average population density of 90 inhabitants/km2 raises to 150 inhabitants/km2 along the main valleys (Buzău, Slănic, Râmnic). The direct result of population increase has been land degradation by overloading the slopes, changing the drainage pattern, overgrazing – actions encouraged by changes in land administration and ownership, especially after 1989.Being one of the most populated regions of Romania, with a developed network of villages spread along a dense river system, the region is at the same time one of the areas most affected by multiple hazards, among which landslides, floods and earthquakes are the most important ones. The presence of numerous elements at risk (villages, isolated households and a dense road network) requires appropriate hazard assessment and mapping for risk management and governance.
The local signals of climate change are sustained by several aspects: a slight increasing trend in annual mean temperatures, a decrease in precipitation and a tendency of rainfall concentration over short time intervals along with increased torrential character. The result is enhanced slope instability, expansion of geomorphic processes, and a large number of flash flood events in small catchments. |