Port activity is economically vital—and becoming more so—to the coastal cities of Charleston [1], Savannah [2], and Brunswick. In addition, the submarine channel at Kings Bay Naval Base off St. Marys, Georgia, must be kept navigable. The downside of such large-scale industrial dredging is twofold:
1) The deeper the channel, the farther upstream salty ocean water pushes. This destroys freshwater and brackish habitats such as the salt marsh.
2) Deepening the channel increases both the volume and the velocity of the river, quickening erosion of the riverbanks.
Links:
[1] http://www.moon.com/destinations/charleston-savannah/charleston
[2] http://www.moon.com/destinations/charleston-savannah/savannah