1 Floods in Bulgaria Gergov, George, Filkov, Ivan, Karagiozova, Tzviatka, Bardarska, Galia, Pencheva, Katia National Institute of Meteorology and Hydrology Sofia, Bulgaria
[email protected] Resume We distinguish the torrent floods of rivers as short-termed phenomena, lasting generally for only several hours and in very rare cases – for up to several days. Appropriate scientific methods for their forecasting are lacking. The short duration of the torrent floods, including their formation, do not make possible the organization of effective protection and safety measures. In many cases the inhabitants does not possess the required training to take-in urgent evacuation or adequate reaction. Torrential rainfalls of intensity up to 0.420-0.480 mm/min and duration of up to 15-29 min. predominate. The frequency of rainfalls above 0.300 mm/min accounts between 20-30 and 50-60 cases per year, while in the case of those with intensity above 0.600 mm/min the frequency diminishes to between 7-10 and 25-30 cases per year. The available hydrological information reveals, that irrespective of the ascending drought the frequency and dimensions of the torrent floods remain unchanged. The biggest flood, ever recorded in Bulgaria, was that of 31st aug.-01st sept.1858 along the Maritsa River in Bulgaria when the river banks in the town of Plovdiv have been flooded by 1-1.2 m. of water. The most ancient data for a devastating flood comes from the Turkish novelist Hadji Halfa. It concerns the Edirne (Odrin) flood in 1361. Numerous digital parameters of the floods are used in hydrology, like for instance, time of rise and time of fall of the flood, achieved water level maximum, average and maximum flow speed of the water current, size and duration of the flood, frequency and duration of the emergence, ingredient of the free water surface, time of concentration and time of travel (propagation) of the high flood wave, depth and intensity of the rainfall, state of the ground cover, preliminary moisture content of the watershed basin, etc.