Application of the HSPF Model for Flood Simulation with Analysis of the Results in Terms of Monitoring Uncertainties /Case Study of the Lesnovska River, Bulgaria/

Floods are amongst the most damaging natural disasters worldwide. The newEU Floods Directive and the implementation of the EU Adaptation Green Paper willrequire improving of the flood-related research. In this study, the HSPF model was appliedto simulate and analyze a very significant and unexpected flood occurred in 2005 along theLesnovska River, a right tributary of the Iskar mainstream in the western part of Bulgaria.The difference between the simulated and the measured flood volumes was found veryhigh and equal to 130% for the flood of 2005, while percent differences of 25-33% wereobserved for the seasonal, annual and low flow distribution. These results were comparedwith an application of the same model for another part of the river system and anotherflood event in order to find explanation of the discrepancies. The monitoring uncertaintiesare discussed to be the main reason of the unsatisfactory model performance for the floodoccurred on August 2005. On the basis of the obtained results, the flow was recalculatedand the probable values of the peak flow were estimated. The needs of implementation ofnew monitoring practices and technoquies for better flood event knowledge and modelingare outlined.