Note 652 — Chapter XI · —The Anthropo-Geography Of Rivers

The historical importance of a river increases from its source toward its mouth. Its head springs, gushing from the ground, and the ramifying brooks of its highland course yield a widely distributed water supply and thereby exercise a strong influence in locating the dwellings of men; but they play no part in the great movements and larger activities of peoples. Only when minor affluents unite to form the main stream, enlarge it in its lower course by an increasing tribute of water, and extend constantly its tributary area, does a river assume real historical importance. It reaches its fullest significance at its mouth, where it joins the world's highway of the ocean. Here are combined the best geographical advantages—participation in the cosmopolitan civilization characteristic of coastal regions, opportunity for inland and maritime commerce, and a fertile alluvial soil yielding support for dense populations. The predominant importance of the debouchment stretch of a river is indicated by the presence of such cities as London, Rotterdam, Hamburg, Bremen, Bordeaux, Odessa, Alexandria, Calcutta, Rangoon, Bangkok, Hongkong, Canton, Nanking and Shanghai, Montreal and Quebec, New York, Philadelphia, New Orleans, Buenos Ayres and Montevideo. This debouchment stretch gains in practical value and hence in permanent historical importance if it is swept by a scouring tide, which enables the junction of inland and maritime routes to penetrate into the land. Even Strabo recognized this value of tidal reaches.652 Hence in tideless basins like the Baltic and Caribbean, the great river ports have to advance coastward to meet the sea; and the lower course of even mighty streams like the Volga and Nile achieve a restricted importance.653