The first section of this diploma thesis pursues an algorithm design of flood wave transformation in Excel software and its application afterwards. The software is used to design a small multipurpose reservoir. The algorithm covers consumption calculations of typical dam structures such as discharge structures, sluice planks, narrowed section of discharge pipes and safety spillways. The thesis also includes a mathematical model of water infiltration into the bottom of the inundation area and through the dam body. The last section of the thesis is dealing with an aesthetic integration of the whole structure into the local environment.