Flood — Fremont, Iowa

2011-08-01 to 2011-08-31 · near Bartlett, Fremont, Iowa

Event narrative

Flooding along the Missouri River gradually worsened over the area during June into July as record inflows into the Missouri River above Sioux City in June and much above normal inflows during July prompted record releases from Gavins Point Dam. The river at Nebraska City reached a record crest of a little over 28 feet by the end of the June before falling through early July as levees in the area were breached and widened by flood waters. Although moderate flooding still persisted into August, river values started falling by the end of the month and minor flooding continued into September as outflows from Gavins Point were reduced. River values at Nebraska City started August a little over 23 feet and ended the month a little over 20.5 feet. Flood stage at Nebraska City is 18 feet. The levee west and southwest of Hamburg failed in June as did the levee near Percival causing extensive flooding of farmland, roads and a few highways near Hamburg, including 24 miles of Interstate 29. Highway 2 that led into Nebraska City also closed by the middle of June due to flood waters and remained closed through September. By the middle of June just under 1,000 people had been evacuated along the river in the Hamburg area and at least 10 businesses had closed. Sandbagging and development of a second levee near Hamburg kept much of the flood waters out of that town during July and August, and the mandatory evacuation was changed to a voluntary one by late August as the river level dropped and pressure on the levee near town was reduced. Around 600 people in Percival, Bartlett and Paul were evacuated toward the end of June after the levee near Percival failed. By the middle of August, as the water had receded slightly, it was learned that erosion had impacted the integrity of some of Interstate 29, especially near bridges and overpasses. The Iowa Farm Bureau Federation estimated that the flood event caused total crop and economic losses of $52.2 million in Fremont county.

Wider weather episode

A record rain event in May in eastern Montana combined with high water from storms in April and May, plus snow melt from a much above normal snow pack, all contributed to bring record high water to the Missouri River chain of reservoirs by late Spring. Then residual snow melt and additional rains produced record 13.8 million and 10.0 million acre feet of runoff above Sioux City in June and July respectively. This helped contribute and sustain record releases from the Missouri River Reservoirs from mid June into early August. Releases from Gavins Point Dam, which is the last in the chain, reached around 160,000 cfs by the middle of June and remained that high into early August before dropping to around 90,000 cfs by the end of the month which help alleviate some of the flooding. The flooding continued into September but moderated greatly. By the end of September the Omaha district of the U.S. Army Corps of Engineers estimated it spent $56 million directly and indirectly in battling the river throughout its share of the basin. In western Iowa 46 miles of Interstate 29 were closed due to flooding and around 250,000 acres of farmland were inundated. The Iowa Farm Bureau Federation estimated that the flood event caused total crop and economic losses of $207 million in southwest Iowa.

View location on OpenStreetMap → (40.8913, -95.8269)

Source: NOAA Storm Events Database, event_id 323005. Narrative written by the NWS forecast office that issued the report.