The Missouri River Valley area has been the object of flood or near floods several times in the past decade, including in Bismarck and Mandan, North Dakota. The flooding in 2009 resulted in the eventual explosion of an ice jam blocking the river. Flooding is a consistent concern in the area.
Bismarck and Mandan are historically not prone to flooding. The last major flood in the area was in 1952 at 27.9 feet and before that, the largest recorded flood was in 1883. The National Weather Service states the 1952 was fourth-highest river level. The highest level was recorded in 1883 at 31.6 feet. Flood stage begins at 16 feet.
In 2009, an ice jam on the river threatened major flooding in the region and caused the evacuation of 1,700 residents. The governor of the state authorized explosives to break the ice jam to prevent the river from overflowing the banks.
While the major flood stage of 16 feet seems low, any amount over that can result in major damage to area homes and businesses. Snowfall and frost levels affect the potential for flooding in that it limits absorption of the winter moisture and can bring on potential flooding.
While the Missouri River at Bismarck and Mandan is not historically prone to flooding, the weather service monitors snowfall and because of the geography of the area. Limited snow melt can lead to overland flooding. Overland flooding is caused by the melt runoff and has limited area to spread.
In most cases, sand bags or floodwalls are used to prevent flooding. While permanent structures are the most effective, short-term walls of sandbags have been used.
