This diploma thesis deals with a design of the reconstruction of a smixed weir on the Oslava river in Oslavany town. The introduction describes the site of interest and the the occurrence of ice events. There are several types of fish ladders described theoretically. Further on in the thesis there is desribed the state of the objects on the flow and the state of the river basin in the area of interest of Oslava river. Next part of the thesis deals with the design of a movable baying structure (a hollow flap) and fish ladder type bypass channel. An impact assessment of the current and newly proposed weir on flow in the HEC-RAS program was carried out. The project also includes the basin adjustment in overweir and an evaluation of the stabili...