This paper explores the problems caused by human impact with settlements and infrastructure in the surface water bodies, especially in potential flood plans. Moreover, the principles and obligations of the EU Flood Directive (2007/60/EC), which supplements the Water Frame Directive, are discussed. The principles and obligations of this directive have been introduced in Slovenia by local legislation: Decree on conditions and limitations for constructions and activities on flood risk areas (OG RS, No. 89/2008) and Rules on methodology to define flood risk areas and erosion areas connected to floods and classification of plots into risk classes (OG RS, No. 60/2007). Some features and obligations of state-ofthe-art hydraulic mathematical models for surface water dynamics simulation are described. Several problems encountered in developing the models and simulating problems are described; these involve using temporarily available geodetic data of the river beds and flood plans and some suggestions for improving of the modelling are made.