A record rain event in May in eastern Montana combined with other storms in April and May plus early spring snow melt and brought record high water to the Missouri River chain of reservoirs.  Heavy rain events and late season snow melt contributed to record runoffs above Sioux City in June of 13.8 million acre feet, and in July of 10 million acre feet.  These all contributed to record releases from the Missouri River Reservoirs.  Releases from Gavins Point Dam, which is the last in the chain, increased to around 160,000 cfs by the middle of June and remained that high through July.  The previous record release was 70,000 cfs. The high releases and periodic rains produced flooding which gradually worsened from May into June and then continued through July and into August.  The river near Nebraska City, which is normally a little over 1,000 feet wide, widened to a channel of more than 2.6 miles with some holes over 60 feet deep.  The flooding closed around 40 miles of Interstate 29 in western Iowa and also several other highways and highway bridges along the river.

Flood in HARRISON, IOWA
From 01-JUL-11 00:00:00 to 31-JUL-11 23:59:00 (CST-6)
Location: RIVER SIOUX
Flood cause: Heavy Rain / Snow Melt
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Flooding along the Missouri River gradually worsened over the area during June and continued into July 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 before falling slightly during July.  However, moderate flooding persisted through July and into late August before river levels began to fall. County roads and at least one highway and parts of Interstate 29 were flooded as were 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.  Highway 30 west of Missouri Valley had to have a temporary barrier of large sandbags installed on both sides to keep flood waters at bay that reached the area from a downstream breach. However, anytime heavy rain would fall in that area water would pond on the highway causing a temporary closure.

Flood in POTTAWATTAMIE, IOWA
From 01-JUL-11 00:00:00 to 31-JUL-11 23:59:00 (CST-6)
Location: GRABLE
Flood cause: Heavy Rain / Snow Melt
Property damage: 3.00M
Crop damage: 0.00K
Reported by: Official NWS Observations

Flooding along the Missouri River gradually worsened over Pottawattamie county during June and persisted into July 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 before falling slightly early in July before reaching a second peak around 36 feet in late July before falling slightly by early August.  The flooding in Pottawattamie county closed 16 miles of Interstate 29 north of Council Bluffs and also closed I680 from the Mormon Bridge to its junction with I29 near Crescent.  Several parks and recreation areas were also flooded along with the parking lots and parts of the parking garage of 2 riverboat casinos.  Other county roads and farm land near the river were also flooded.  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.  Some homes near the river experienced seepage into basements from high ground water levels.  The flooding continued into August.  As of early July the city of Council Bluffs had spent or committed over 5.5 million dollars for flood relief/prevention.

Flood in MILLS, IOWA
From 01-JUL-11 00:00:00 to 31-JUL-11 23:59:00 (CST-6)
Location: FOLSOM
Flood cause: Heavy Rain / Snow Melt
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Flooding along the Missouri River gradually worsened over the area during June into July as record releases from Gavins Point Dam brought widespread flooding along the River. At Plattsmouth the river started June around 30 feet, flood stage is 26 feet, and eventually reached a little over 36 feet by the end of the month before falling a little in July.  However, at least moderate flooding persisted well into August.  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, some due to mandatory evacuations west of I-29 since rising ground water caused impassable county roads blocking possible evacuation routes.

Flood in FREMONT, IOWA
From 01-JUL-11 00:00:00 to 31-JUL-11 23:59:00 (CST-6)
Location: BARTLETT
Flood cause: Heavy Rain / Snow Melt
Property damage: 150.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Flooding along the Missouri River gradually worsened over the area during June as record releases from Gavins Point Dam and periodic heavy rain brought widespread flooding along the River. The river at Nebraska City reached a record crest 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.  However, significant flooding persisted through much of July and August.  A levee west and southwest of Hamburg failed by the middle of June causing extensive flooding of farmland, roads and a few roads or highways near Hamburg, including 10 miles of Interstate 29.  By mid July around 24 miles of Interstate 29 was closed, from around Bartlett to the Missouri border.  Highway 2 that led into Nebraska City also closed by the middle of June due to flood waters and remained closed in July.  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.  Around 600 people in Percival, Bartlett and Paul were evacuated toward the end of June and on June 30th the levee near Percival failed causing additional flooding and closing of more of Interstate 29.  By the end of July the levee breach near Percival expanded from 200 feet in late June to around 1,000 feet by the end of July.

Flood in MONONA, IOWA
From 01-JUL-11 00:00:00 to 31-JUL-11 23:59:00 (CST-6)
Location: ALBATON
Flood cause: Heavy Rain / Snow Melt
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Flooding along the Missouri River gradually worsened over Monona county during June and continued through July as record releases from Gavins Point Dam brought widespread flooding along the River.  Flooding in Monona county initially was mainly confined to agricultural lowlands, recreation areas and roads near the river but then started threatening Blencoe which 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 and closed 2 casinos.  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.  The flooding persisted into August.