Flooding in Iowa, August 1 to 31, 2011

Flooding along the Missouri River gradually worsened over Monona county during June and July as record releases from Gavins Point Dam brought widespread flooding along the river. Conditions improved markedly during August as releases were reduced and the river level at Decatur dropped below flood stage late in the month. Flooding in Monona county was mainly confined to agricultural lowlands, recreation areas and roads near the river. However, Blencoe started sandbag operations in June as did other businesses from Blencoe to Onawa. The flooding forced the post office in Blencoe to move operations to a nearby town. Late in June the Highway 175 bridge over the Missouri between Decatur and Onawa was closed due to erosion of the abutment on the Iowa side of the bridge and the bridge and highway remained closed through August. The Iowa Farm Bureau Federation estimated that the flood event caused total crop and economic losses of $32.3 million in Monona county.

Flooding along the Missouri River gradually worsened over the area during June and July and continued into August as record releases from Gavins Point Dam brought widespread flooding along the River. The river near Blair climbed to a little under 33 feet by the end of June, flood stage is 26.5 feet, before falling slightly during July and a little more in early to mid August. However, by late August decreased releases from Gavins Point Dam had allowed the river near Blair to fall to around 28 feet. County roads and highways, some homes and farmland and parts of Interstate 29 were flooded along with several parks and recreation areas near the river. Sand bag operations were used near Missouri Valley, Modale and Mondamin where at least 100 to 200 voluntary evacuations of residences occurred. The flooding forced the post office in Modale to move operations to a nearby town. Large TrapBags placed along Highway 30 west of Missouri Valley to stop flood waters from backing up from a downstream levee breach would trap water from any heavy rain event causing flooding and its temporary closure, including a severe storm/heavy rain event on Aug. 18th. Although river levels started dropping by the end of August, minor flooding persisted into September. The Iowa Farm Bureau Federation estimated that the flood event caused total crop and economic losses of $36.7 million in Harrison county.

Flooding along the Missouri River gradually worsened over western Pottawattamie county during June and July and persisted into August as record releases from Gavins Point Dam brought widespread flooding along the River. The river near Omaha climbed to a little under 36 feet by the end of June, flood stage is 29 feet, before falling slightly in July and a little more by early August. By the end of the month decreased releases from Gavins Point Dam had allowed the river to fall to around 31 feet. The flooding in Pottawattamie county closed roads along the river including 16 miles of Interstate 29 north of Council Bluffs and Interstate 680 east of north Omaha. Several parks and recreation areas were flooded along with parking lots and parts of the parking garages of 2 riverboat casinos. At least 100 homes in Council Bluffs were evacuated and about 10 businesses were closed. Tens of thousands of sandbags were filled and deployed to help shore up weak spots in the federal levee in the Council Bluffs area which came close to failing in July. Some homes near the river experienced seepage into basements from high ground water levels. Although river levels had dropped by the end of August, minor flooding persisted into September. The U.S. Army Corps of Engineers stated that a little over $6 million was spent on levee repair/work in Pottawattamie county. As the river fell by the end of August it became apparent that Interstate 680 had been undercut by the current completely destroying the pavement from the river to its junction with I29 near Crescent. The Iowa Farm Bureau Federation estimated that the flood event caused total crop and economic losses of $ 31.2 million in Pottawattamie county.

Flooding along the Missouri River, which had gradually worsened over Mills county during June and July, persisted into August. However, conditions began improving by the end of the month as record releases from Gavins Point Dam were gradually reduced during August, especially by the end of the month. At Plattsmouth the river reached a crest of a little over 36 feet by the end of June, flood stage is 26 feet. The river level near Plattsmouth fell a little in July and a bit more in early to mid August. By the end of August the river had fallen to around 30 feet. The flooding affected farmland along the river along with roads and recreational areas. The water treatment plant and wellheads near Glenwood were sandbagged to prevent flood waters from reaching it. By the middle of June about 125 of the 500 residences along the river had left their dwellings. Although river levels were falling by the end of August, minor flooding persisted into September. The Iowa Farm Bureau Federation estimated that the flood event caused total crop and economic losses of $22.2 million in Mills county.

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.