The graduation thesis describes the problem of one of the Vrtojbica streams' tributaries. The source of the tributary stream is located on the Mark hill in Šempeter pri Gorici. The canal is almost empty most of the time, but in case of heavy rainfall, the stream floods the road under which it flows. The reason of flooding is the inlet of the culvert under the road. The following sections, the problematic section of the stream and the proposed solutions are described. The basic idea is to hold the water as upstream as possible and locally restrict the downstream flow to the limit of the culvert acceptance. The gathered data on the stream as well as maximum rainfall data have been used to define the surface runoff for each tributary of the stream for 5-, 10- and 50-year rainfall extremes. After calculation of maximum inlet flow into the road culvert, the amount of excessive water to run into the designed flooding area is calculated. The graduation thesis includes both, hydraulic calculations as well as photographs of the stream in normal, flooded and after-flood conditions.