Navigation Analysis at the Entrance to the Bypass Channel of Siarzewo Barrage

Navigation safety is the most important issue on any waterway. Plans to use the lower Vistula as an inland waterway came from the 1960s. As the first stage of regulation works, the Włocławek barrage, located at 674.850 km, was constructed in the years 1962–1970. At present, further regulation by constructing the second barrage in Siarzewo (706.380 km), is under consideration by the State Water Holding Polish Waters. The ongoing analysis covers all elements of barrage composition, including weirs, hydro-power station, fish passes, a bypass channel, and a twin lock. The design of the proposed barrage assumes a lock to be situated on the right riverbank. The proposed distance between the entrances to the upper lock and the bypass is relatively small, not exceeding 50 m. This fact raises navigation concerns due to a possible interaction between river flow along the navigation channel and inflow to the bypass. In-situ observations of navigation channels show the negative influence of a crossflow on ship trajectory, leading to reduced navigation safety. Analysis of hydrodynamic conditions at the entrance to the bypass channel at Siarzewo barrage, and their influence on vessel maneuverability are presented.