Size of the Watershed: Each river is a different size covering many miles of creeks and streams that feed the main branch. With todays google maps, one can get a great picture of home much real estate a river really holds. The more, the longer it takes to clear.

River Gradient: Each river tumbles down to Lake Erie faster/slower than another. A good topo map can give you clues to how fast it rushes downstream. More gradient, the faster it clears.

Watershed Variables: The midwest is a populated area. Some rivers run through more forest than other. When water runs on ground, stable forestland will trap sediment more efficiently than farmland. Rivers with more city land tend to run-off faster than rural areas do.