The river is beginning to meander and has a wide flood plain. Actually, this river in Indiana deepened its valley when Pleistocene sea level fell, then filled it in again as sea level rose. It probably also widened and streamlined its valley by carrying huge amounts of glacial melt water. This area wasn't glaciated, but the valleys were probably deepened and then filled in during Pleistocene sea level changes. A classic old age meander in central Wisconsin, except that the flat land was the bed of a glacial lake only 12,000 years ago.
Rivers meander when the land is flat.
One reason the land may be flat is that the landscape is very ancient, but some very young surfaces can also be flat. The San Juan River in Utah is a classic example of rejuvenation. The river must have been meandering on a flat landscape and then begun cutting downward. Landscapes can be rejuvenated at any time. But the valley bottoms are so young that valley widening has scarcely occurred.