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Abstract:

In the summer of 1969 the Bașeu River (an important tributary of the Prut River in the north-eastern extremity of Romania) recorded historical floods due to heavy rainfalls (about 100 mm/m²/24h) falling in its hydrographic basin. The maximum flow rate, recorded at Ștefănești gauging station, was 330 m³/s and associated with a level of 535 cm in the lower floodplain area. The flood event affected the joint floodplain sector of Başeu and Prut rivers on a width between 2–3 km and, implicitly, five settlements: Stânca, Ștefănești, Bădiuți, Bobulești, Românești. The main objective of this study is to reconstruct the historical flood of 1969 and its effects, as well as to evaluate the flood hazard in case of repeating an event of the same magnitude in the current context and comparing them. Thus, using the HEC-RAS software, we developed two 2D hydraulic scenarios (2D-HS) based on the July 1969 flood hydrograph from the Ștefănești gauging station (on Bașeu River) and Stânca gauging station (on Prut River). In the first 2D hydraulic scenario (2D-HS1) we used the buildings and the land use categories extracted from the topographic maps (1972-1979 edition), while in the second 2D hydraulic scenario (2D-HS2) we used the buildings and the land use categories from the orthophotos (2015 edition). Additionally, we assessed the flood hazard severity for each 2D-HS. The results showed that after the 1969 flood event, the built-up area has narrowed its surface. The constructed area affected by the 1969 flood event was converted to arable land or pasture. In the case of the 2D-HS1 291 buildings were affected and in the case of 2D-HS2 just 234 buildings would be affected. According to flood hazard classification, for both 2D-HS, more than 50% of the affected buildings are located in the first hazard class (with a flood depth <0.5 m). The highest class of flood hazard (flood depth >5 m) corresponds to the Prut River channel and other abandoned meanders of the old course of the Bașeu River.