Exceptional floods on a developed river: case study for the Bistrita River from the Eastern Carpathians (Romania)

The geographical position of the Bistrita River favours a rich liquid run-off and great hydrotechnical potential. The Bistrita drainage basin is strongly developed from the hydrotechnical point of view. Within the drainage basin, numerous dams and storage reservoirs are installed with the purpose of producing electricity and reducing flood hazards. However, these structures could not stop floods at the drainage basin level. The most powerful floods from Bistrita River basin and the role in flood control of each of the storages are analysed in this paper. The hydrological data have been collected from the monitoring network, where the researchers elaborating this study are performing their daily activity. The most powerful floods in the last century took place in 1970, 1991, 2005 and 2010. An intensification of the floods can be noticed after the year 1990, a period which coincides with large-scale deforestation of the small drainage basins. Disastrous floods occurred as a consequence of summer heavy rains, with amounts of 100-200 mm within 24 h. The most powerful floods were recorded in 2005 and registered discharges up to 1,200 m(3)/s. Izvoru Muntelui reservoir, the biggest in the system, can take most of the waters in excess. The reservoirs located downstream are silting up, and the supplementary flows cannot be absorbed entirely by storage. The exact knowledge of flooding phenomena requires studies that can prevent and diminish the damages caused by extreme hydrological events.