The area is greatly diversified with low rolling hills, upland flats, and narrow valleys. Steep slopes occur where the encircled Nashville Basin cuts into the area and along the western edge bordering the Coastal Plain. Elsewhere, except for steep walls and hillsides along deeply cut stream channels, the topography is predominantly gently rolling to strongly rolling with a few interruptions by broad upland flats and shallow basins. In many places the land surface is pitted by limestone sinks. Average annual precipitation -1,125 to 1,375 mm.
Maximum precipitation is in winter and early in spring, and the minimum is in fall.
In most years, precipitation is adequate for crops, but in some years, yields are reduced by short dry periods early in summer. The numerous perennial streams and lakes supply abundant water to much of the area. Several medium to large lakes constructed by the U.S. Corps of Engineers provide flood control, power production, recreation, and water for municipalities. In some parts where surface water is scarce, the water comes mainly from wells, large springs, and farm ponds. In many places, waterlines from metropolitan areas extend far into the countryside.