The levee on the Wisconsin River had deteriorated in the Town of Caledonia, just west of Portage, after recent thunderstorms bloated the waterway.
Water is beginning to leak through at certain points of the levee. Greg Matthews, a spokesman for the Wisconsin DNR, said that some of the levee could begin to collapse.
The levee is part of the Caledonia-Lewiston Levee System. The Wisconsin Department of Natural Resources says the system is made up of several dikes built mainly out of sand during the 1890s by homeowners living near the river.
If the levee breaks it could destroy an already flooded access road to the town's Blackhawk Park neighborhood. Some 75 of 300 area residents have decided to stay in their homes.
Some pictures of the flooding in Portage Wisconsin.