The stream is young geologically, and only in places where the glacial material has been removed is the underlying bedrock exposed.

[1] The headwaters of the Cedar River are located in Dodge County, Minnesota, consisting of a west fork and middle fork approximately three miles northeast of the town of Blooming Prairie, and an east fork approximately one mile south of the town of Hayfield.

At Conesville, Iowa, the Cedar River is approximately 5,798 cubic feet per second.

[6] Upriver, the Waterloo-Cedar Falls metropolitan area was less affected, thanks mainly to the large dikes that protect the downtowns of both cities.

To the north, the flooding Cedar River collapsed Charles City's landmark suspension bridge, as well as destroying many homes and community parks.