Lock approaches optimization to improve waterway traffic capacity

The traffic capacity of a waterway on canalized rivers is usually determined by the transit time through the locks. Total transit time of a vessel through a lock is influenced by a number of aspects, including the time taken to open the lock gates, the time taken to fill and empty the lock and the time taken for vessels to enter and exit the lock. This paper deals with the optimization of lock approaches. If the navigation conditions in the lock approach are suitable, it is possible to ensure relatively easy manoeuvrability of vessels and the time interval to enter and exit the lock can be significantly reduced. The navigation conditions in the lock approach are influenced significantly by the flow conditions in the vicinity of the guard wall. The guard wall separates the lower and upper lock approaches from the gated weir and, if not designed appropriately, there can be significant flow velocity which tend to pull vessels toward the guard wall and weir. In addition to flow conditions, pilot experience, engine power and wind speed also affect the manoeuvrability of vessels in the lock approach. This paper presents a procedure to optimize the guard wall by achieving appropriate flow conditions in the lock approach using a mathematical 2D (depth-averaged) model. As a suitable measure, a flow-through multicell (ported) guard wall is proposed, which has flow openings between the cells designed below the draft level to limit the transverse flow velocity per vessel in the vicinity of the guard wall. The presented optimization procedure was verified on the case study of the Modrany lock in Prague (Czech Republic). The Modrany barrage was built in 1979-1987 on the Vltava River and at high flows the manoeuvrability of ships is considerably reduced with a decrease in the capacity of the waterway. The application of the proposed procedure led to the extension of the multicell guard wall with the application of flow-through openings. This solution made it possible to ensure significantly better flow conditions in the upper lock approach and was subsequently also verified in a physical model in the hydraulic laboratory. The implementation of this measure in situ is currently under preparation. The described technical solution has minimal impact on the architectural character of the lock and can therefore be used to increase the capacity of the historic locks on the Elbe-Vltava Waterway in the Czech Republic. The research was conducted as part of project no. DG18P02OVV0