Note 649 — Chapter XI · —The Anthropo-Geography Of Rivers

In the trade-wind regions of the world, which are characterized by seasons of intense drought, we find rivers carrying a scant and variable amount of water but an abundance of gravel and sand; they are known in different localities as wadis, fiumares and arroyos. Their beds, dry for long periods of the year, become natural roads, paved with the gravel which the stream regularly deposits in the wet season. Local travel in Sicily, Italy649 and other Mediterranean countries uses such natural roads extensively. Trade routes across the plateau of Judea and Samaria follow the wadis, because these give the best gradient and the best footing for the ascent.650 Wadis also determine the line of caravan routes across the highlands of the Sahara. In the desert of Southwest Africa, the Khiuseb Is the first river north of the Orange to reach the Atlantic through the barrier dunes of the coast. Hence it has drawn to its valley the trade routes from a wide circle of inland points from Ot-tawe to Windhoek and Rehobeth, and given added Importance to the British coast of Walfish Bay, into which it debouches.651 But just to the north, the broad dry bed of the Swakop offered a natural wagon route into the interior, and has been utilized for the railroad of German Southwest Africa.