Zambezi the overflow of the Zambezi in the rainy season. The delta of the Zambezi is today about half as broad as it was before the construction of the Kariba and Cahora Bassa dams controlled the seasonal variations in the flow rate of the river. Before the dams were built seasonal flooding of the Zambezi had quite a different impact on the ecosystems of the delta from today as it brought nutritious fresh water down to the Indian Ocean coastal wetlands. The lower Zambezi experienced a small flood surge early in the dry season as rain in the Gwembe catchment and
Zambezi east. Here, the river is broad and shallow, and flows slowly, but as it flows eastward towards the border of the great central plateau of Africa it reaches a chasm into which the Victoria Falls plunge. 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