Straightening rivers not only increased the speed with which barges and other river traffic are able to move, but also increases the speed of the river itself. The faster the water moves downstream the greater the likelihood of flooding. The construction of dikes and levees may have the largest impact on downstream flooding. Every dike built reduces the area over which a river may spread out. While flooding may be reduced in the upper reaches of a river, the effect is to force more and more water into a smaller and smaller area.
Dikes downstream have to be larger and higher to cope with the increased amount of water.
When flooding does occur, upstream dikes force more water downstream and thus contribute to larger and more destructive floods. With far fewer economic resources than a country like the United States, a major flood in the Hidrovia countries would be relativley more devastating. The Pantanal represents a pristine wetland area in southwestern Brazil. It extends as an immense, kidney-shaped lowland compromising Upper Paraguay in western Brazil, eastern Bolivia and northeastern Paraguay. This area represents one of the world's most ecologically diverse areas.