Flood — Fremont, Iowa

2011-09-01 to 2011-09-28 · near Hamburg, Fremont, Iowa

Event narrative

Flooding along the Missouri River gradually improved over the area during September as releases from Gavins Point Dam were reduced. The river at Nebraska City, which reached a record crest of a little over 28 feet by the end of the June, had fallen to around 20.5 feet by the first of September and finally below its 18 foot flood stage during the evening of Sept. 28th. However, extensive flooding of farm fields, roads and highways that had occurred over the summer as levees near Hamburg and Percival failed persisted into September. The flooding caused the closure of 24 miles of Interstate 29 and Highway 2 into Nebraska City as well as other local roads and highways. After the flood waters receded, it was learned that Highway 2 near I29 had several areas of extensive damage, included a sink hole of 15 feet deep. Bridge approaches along I29 were damaged just north of the Missouri border. These roads remained closed in September.

Wider weather episode

A record rain event in May in eastern Montana combined with high water from other storms in April and May, plus snow melt from a much above normal snow pack, to bring record high water to the Missouri River chain of reservoirs by late Spring. Then residual snow melt and additional rains caused record 13.8 million and 10.0 million acre feet of runoff above Sioux City during June and July respectively. All of 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 that month. The releases were then held steady for several weeks in early September to help avoid sloughing of water-logged levees. So although flooding continued into September at many points along the river, it moderated greatly. At the floods peak 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 → (40.5922, -95.7211)

Source: NOAA Storm Events Database, event_id 335095. Narrative written by the NWS forecast office that issued the report.