RISCURI I CATASTROFE Vol. VII, Nr. 5 / 2008 Riscuri i catastrofe Victor Sorocovschi 238 DAM-BREAK RISK ASSESSMENT OF DR GAN DAM FROM THE UPPER BASIN OF CRI UL REPEDE CS.HORVÁTH ABSTRACT. – Dam-break risk assessment of Dr gan Dam from the upper basin of Cri ul Repede. Although dams reduce the risk of floods, through their realization appears a potential risk that derives from the possibility of the dam- break. The accidental flood, formed as a result of a dam fail, will have catastrophic consequences. In case of dam-break the registered runoff values can be ten times bigger than the natural floods corresponding to the appearance probability of 0,1 %. In the first part of the study we present the general characteristics of the risks generated by a dam fail. In the second part we present a scenario of the dam- break of the Dr gan Dam from the upper basin of the Cri ul Repede and its possible effects inducted in the down-stream. Key words: vulnerability, technical characteristics, dam, Dr gan, Cri ul Repede. 1. General considerations The risk of a dam-break is formed by the probability of failing and the consequences. To determine the probability of a dam-break, it is necessary to identify and calculate the fail type, also the dam structure loading and resistance. The magnitude of the damages depends on the effected territory social- economic development state and the population density, and from the dam-brake wave characteristics (runoff, volume, speed, duration, level, water column height, length and thickness of the deposits). The causes which provoke the failing of the dam-breaks were grouped in four categories: 1.disregarding the stability conditions, the dam or the foundation couldn’t stand the demanded actions, the failing appearing as tipping, sliding, etc.; 2.disregarding the durability conditions, the dam or the foundation couldn’t stand the demanded actions in time, here we mention the infiltrations, the water internal actions, the climatic and chemical actions; 3.disregarding the operational and functional conditions, the structure can’t satisfy some functions that can trigger the fault (excessive silting); 4.other causes, here are mentioned natural disasters (earth quakes, flash floods) and antropical causes (terrorism, war) etc.