Corps to begin dredging, snagging, removing sunken vessels, and clearing overhanging trees on the Upper Mississippi River (Anfinson, 1993). In the same period, the Corps removed thousands of snags on the Upper Missouri River, where snags and other navigation hazards and impediments claimed almost 1,000 steamers, ferries, and snag boats before the railroads supplanted navigation there (Schneiders, 1999).
Today, the Corps’ water transportation missions extend to the nation’s coastlines and inland rivers. Engineering in the interests of promoting water transportation has moved far beyond removing naturally occurring obstacles in rivers and harbors. To support modern ocean-going shipping, continuous dredging is necessary at coastal ports to maintain approach channels and berthing facilities. On inland rivers and waterways, continuous dredging and the operation and maintenance of water control structures of locks and dams maintain a minimum 9-foot channel throughout the nation’s inland water transportation network. The Corps has also promoted efforts to be responsive to the needs of ecosystems, as in its efforts to fluctuate the levels of navigation pools on the Upper Mississippi River so as to increase hydrologic variability and ecosystem vitality (see USACE, 2004a).
The Corps’ navigation mission to support commerce led to the agency’s involvement in flood control. Congress appropriated money to the Corps as early as 1850 to survey the Mississippi River in the interests of reducing flood damages. The Corps came to view floods as natural events that could be predicted with reasonable accuracy and that could thereby be controlled through engineering practice and investment. Flood control would allow lands unsuited for agriculture to be made productive and would allow cites to grow up along the river transportation system. Flood control was deemed essential to national economic prosperity. The Corps’ early flood control program focused on levees; only later were channel and dam projects integrated into the control of flood waters. In 1879, Congress created the Mississippi River Commission. The commission promoted a “levees-only” policy for managing Mississippi River floods. This policy was based on the premise that levees were sufficient for the control of floods, as it was believed that by constricting a river’s flow and increasing the speed of its current, levees would create a self-scouring process that would allow a river to dredge its own bottom. The levees-only policy remained the basis of Corps