There are several reasons why many South Americans move from rural to urban areas, but in general many do this because there are more opportunities and higher pay in urban areas.
The Tennessee Valley Authority is a corporation that was established as part of FDR's New Deal programs. One of the purposes of this corporation was to avoid the excessive presence of private companies in the modernization of the valley.
The TVA provided people with many jobs during the Great Depression. However, it achieved more than this. The TVA managed the natural environment of the region by controlling flooding and erosion. It also increased industrial activity in the region by building dams and power plants.