sentences:  The Victoria Falls are considered the boundary between the upper and middle Zambezi.Below them the river continues to flow due east for about , cutting through perpendicular walls of basalt 20 to 60 metres (66 to 200 ft) apart in hills 200 to 250 metres (660 to 820 ft) high.The river flows swiftly through the Batoka Gorge, the current being continually interrupted by reefs.