Thesis examines potential project idea in the area of the eastern part of the city of Rijeka. It is an area of town called Porto Baroš where parts of the old port, customs area and Mrtvi kanal are located. Main objective of the paper is to make a hypothetical situation and to estimate reality of making a discharge pipe from the river Rječina towards the Mrtvi kanal, which will ensure its flow. The goal of this idea is to solve problems regarding bacterial concentration, pollution and unpleasant smells in the predominantly stationary channel. For the expected input range, a 3D numerical analysis of the flow in the area of port customs in Porto Baroš was made and visualized results were obtained. The analysis itself and the simulation were preceded by a series of steps that were explained in detail through all the chapters. From everything elaborated and explained in the paper, it can be concluded that the topic is justified and that it is possible to expand it in order to find the right solution for the most environmentally friendly solution in the area.