sentences:  David Livingstone's Zambezi Expedition attempted to open up the river to navigation by paddle steamer, but was defeated by the Cahora Bassa rapids.Along some stretches, it is often more convenient to travel by canoe along the river rather than on the unimproved roads which are often in very poor condition due to being regularly submerged in flood waters, and many small villages along the banks of the river are only accessible by boat.In the 1930s and 40s a paddle barge service operated on the stretch between the Katombora Rapids, about upstream from Livingstone, and the rapids just upstream from Katima Mulilo.