Numerical Simulation of Flood Inundation Scenarios Along the Bistrița River, Following a Hypothetical Failure of the Bicaz Dam, Romania

Dam failures are low-probability but high-consequence events which require hydraulic modelling studies for hazard assessment. A hypothetical failure of the 127 m Bicaz gravity Dam, Romania, is investigated using a 2D model developed in HEC-RAS along a 115 km reach of Bistrita River, in Romania. Six failure simulation scenarios are considered during incoming flood and normal-flow conditions, combined with three rectangular shape breach areas (for a various number of monoliths failure) in case of a sabotage event. The main purpose of the study is to analyse the flood wave dynamics downstream of an area with multiple other smaller dams, dykes, and reservoirs. Peak flow attenuation and arrival times of the front were mainly investigated down to Piatra Neamț and Bacău cities. In the downstream full reservoirs, the velocity and flow hazard increase and water spills over the contour dikes, whereas in an empty reservoir, the flood wave is attenuated, and the same hydraulic parameters decrease. A new reservoir filling time parameter also shows higher values in the empty reservoir. Maximum flood depths, velocities, hazard, and inundation boundaries are examined along the river. A preliminary assessment of hazard and exposure of buildings, performed in QGIS for Piatra Neamț city, shows that the impact of such a flood wave would be catastrophic. The results of this study are very useful to provide information for such a catastrophic failure and to support emergency planning.