The future of rivers, seas and inland waterway

What will be more harmful to the environment: more tons of exhaust fumes emitted by road transport, or interference with the natural course of rivers to turn them into waterways? Are our rivers even suitable for transporting goods? What will it cost and is the game worth the candle? These are all questions with no clear-cut answers. River transport is considered to be one of the least emissive, although not necessarily the greenest, mode of transport. Similar controversies accompany hydroelectric power plants - on the one hand, producing clean, renewable energy. On the other hand, it requires large capital expenditures and tons of concrete. Will we be able to find a solution to this ecological impasse?