This research investigates the possibility of improving the navigation characteristics downstream (D.S.) locks by reducing the cross velocities. Several site visits were carried out to different navigable reaches where D.S. Saryakos Lock was chosen to be taken as a case study to investigate its navigation condition after constructing a new barrage. Different measurements, such as velocities, discharges and corresponding water levels, were undertaken D.S. the lock location. Based on the visits and measurements, a complete data picture was perceived to the study area. Consequently, a physical model was constructed in the Hydraulics Research Institute (HRI) to simulate the lock. The model was calibrated against field measurements that were carried out upstream and downstream the lock. An experimental test program was designed to examine the navigation conditions of the lock by varying the length of the guiding wall separating it from the main barrage under different discharges. Measurements were undertaken at the maximum, minimum and dominant discharges and were analyzed. Based on the results, it was found that the separating guide wall (SGW), with a length of one third of the total channel width, produced a reasonable velocity distribution along and across the channel. This wall length (30 m in this tested case) will lead to a better navigation conditions in the prototype.