The sediment transport of the Siret River during the floods from 2010

Abstract

Beginning with 2004 in the Siret River Catchment there occurred exceptional flash floods that exceeded the maximum historical values recorded, on the main river and on its tributaries (2004, the Trotus River; 2005, the Siret River, the Trotus River, the Bistriţa River, the Putna River; 2006 - the Clit River from the Suceava River Catchment; 2008, the Siret River, the Suceava River). The 2010 summer flood from the Siret River also falls in this category. This paper uses hydrological data (water discharge, suspended sediment discharge) between the 20 th of June and 10 th of July 2010 from 5 gauging stations located on the Siret River: Siret, Hutani, Lespezi, Dragesti, Lungoci, and also meteorological data (rainfall) measured at different gauging stations from the Siret River Catchment. The rainfall recorded in this time of the year in the catchment was very high, with values up to 210 l/m 2 in approximately 10 days. The hydrographs of the flash flood indicate the fact that the transit of the water trough the reservoirs system from the Siret River (Rogojesti - Bucecea and Racaciuni – Beresti –Calimanesti - Movileni) reduced the maximum water discharge with values between 7-27%. The values of the maximum sediment discharge also recorded a reduction while transiting this reservoirs system with approximately 60%. The evolution of the Siret river bed channel during this flood (aggradations with values between 15-100 cm and degradations starting from 65 cm until 200 cm, in different moments of the flood) is influenced by the high values of the water and sediment discharge and by anthropogenic interventions on the river bed (pit-ballast, regularization of the river bed, reservoirs). Processing the hydrological and meteorological data recorded during the flood (20th of June – 10th of July 2010) indicates two important features of this event: the climatic variability – exemplified by the big values of precipitations from the catchment and the anthropogenic impact revealed by the transit of the flood wave and the evolution of the river bed.