Flood analysis using Mike 11 by DHI and ArcGIS. Case study – the flood in the upper catchment of river Geru, Galaţi county, Romania

Between the 11th and 13th of September 2013 large quantities of rainfall occurred in the upper catchment of river Geru. The precipitations have generated a flash flood with three peaks, with the maximum discharges of 118.00 m3/s recorded on 12th of September 2013, 2300. Simulations of the flash flood were performed alternatively with Mike 11 by DHI - NAM (Nedbør Afstrømning Modele) and with MIKE by DHI –UHM, using radar precipitations as input data. Radar rainfall values were generated by ROFFG (Romanian Flash Flood Guidance) software system in ArcGIS module for determining the area affected by flash floods. The program Mike 11 by DHI – NAM accounts for the water content in up to 4 different storages. As default, NAM uses 9 parameters to represent the Surface zone, Root zone and the Ground water storages. The program Mike 11 by DHI – UHM calculates excess rainfall and determines infiltration losses by four methods. The discharge hydrographs simulated with Mike 11 by DHI program were compared to the discharge measured at the hydrometric station. The amplitude and phase errors are directly dependent of the accuracy of the input data and chosen parameters.