 The DNR is closely watching rivers in southern Minnesota where dams were replaced with rock rapids, including Windom, Orinoco, and Jackson. But Childers says they're not worried. The rapids are built to handle a 100- to 500-year flood. In Willow River in eastern Minnesota, the DNR removed a dam after it collapsed in 2016 and replaced it with rapids. Mayor Brent Schweitzer says this year there's more water rushing over the rocks.