Master's thesis aims to design a small water reservoir. It is the dry water reservoir which is situated above a built-up area. The main function of this reservoir is a flood protection. Digital terrain model is created in a program BENTLEY MicroStation V8i – Power Civil. Focusing points in a data file are used in a process of creating of the DTM. Adjustments are done in AutoCAD. Particular hydro-technical calculations are calculated in a program Microsoft Excel. A program HEC-HMS is used for an assessment of a flood wave transformation and a program HEC-RAS is used for a water runoff simulation via emergency spillway.