Hydrologic hazards generating emergency situations in the middle mountainous sector of Bistriţa valley

Abstract

Beginning with the end of the 20th century, with the rise of the mean air temperature by 0.6–0.7ºC, a significant increase in the frequency of extreme natural phenomena (mainly thermal and rainfall-related ones, generators of emergency situations) was triggered. The present paper analyzes the most important hydrological risks manifested in the mountainous middle sector of Bistriţa valley, with negative consequences (large material damage and human life losses). The middle mountainous sector of Bistriţa valley is a narrow couloir on whose bottom the river meanders between the abrupt slopes of two mountain areas with maximum altitudes of 1,859 m (Budacu Peak in Bistriţa Mts.) and 1,529 m (Bivolul Peak in Stânişoarei Mts.). Bistriţa is the river with the longest mountainous course in Romania, its length in the eastern Carpathians being of 216 km, over 2/3 of its total. In this sector, but mainly between Vatra Dornei and Poiana Largului, the ice jam phenomena are the most frequent and intense on all Romanian rivers. In the analysis of the main hydrological hazards (floods due to torrential rainfall and winter ice jams), whose frequency has increased significantly during the last three decades, data were used from Piatra Neamţ, Ceahlău - Sat and Ceahlău Toaca meteorological stations as well as from other hydrometric stations and rainfall gauges. There were also used references on the climatic features of the middle basin of Bistriţa or larger areas including it, the factors that may influence the occurrence and evolution of hydrological and climate phenomena with risk potential, or those needed to define some notions (hazard, risk and emergency situation).