Koenraad Verboven (Ghent University), Rivers and lakes in the Roman transport economy

Most modern scholars follow the opinion of ancient authors that transport by river (and lakes) was more efficient, profitable and cheaper than land transport. Archaeological data showing the transport routes for ceramics and stone cargoes, seem to confirm this idea. The epigraphically documented prestige enjoyed by the Barge-skipper guilds in Narbonensis, Germania Superior, and southern Lugdunensis further support that picture.
But the efficiency of river and lake transports is far not evident. Basins are not naturally connected. Without roads the contribution of riverine trade to overland transport networks is doomed to remain limited. Waterfalls, narrows, and rapids obstruct navigation. Levels and flows depend on unpredictable rainfall. River banks erode. Sediments change the course of rivers. Rivers and lakes may freeze in winter or run dry in summer. Currents hamper upstream traffic. Administrative divisions also pose problems related to different regulations, control procedures, and water management practices, tolls and fees. Barges are vulnerable to attacks by land from brigands, raiders or soldiers. Without tow-paths, canals, portages, locks, connecting roads, ports and warehouses, rivers offer only a marginal contribution to trade. Riverine transport routes are as much man-made as roads are. What does this imply for the supposed efficiency of river and lake transport in the Roman period?