Summary:

1-dimensional models, e.g. HEC-RAS, MIKE 11 are used to calculate water surface elevation concerning probable discharges for flood hazard areas designa-tion. Hydro-informatic software programs HEC-RAS and MIKE 11 are used for modeling of water discharge in the river bed and in the river valley, with engineer-ing objects of complicated structure (bridges, culverts, weirs etc.). The following stages of modeling may be distinguished: schematisation of water network, geodetic measurements of the river bed and engineering buildings, identification of roughness coefficients, hydrological calculations of discharges in selected profiles of the modelled watercourse considering the boundary conditions, numeric calcu-lations with calibration and verification of the model as well as visualisation of the calculations' results.
The paper presents the results of modeling of a sector of The Lubcza River in the Wislok basin having length equal 8,7 km (uncontrolled basin), in which
17 bridges and 12 weirs are located. The elevations of the water surface for di-scharges of the defined probability of exceedances and the Digital Model of the Water Surface (DMWS) are the basis for the analyses and comparison of the obta-ined results. Flood hazard areas occur on the intersection of the Digital Terrain Model (DTM) and DMWS. The knowledge of water surface permit the destination of the flood hazard areas.