A record rain event in May in eastern Montana combined with high water from other storms in April and May and brought high water to the Missouri River chain of reservoirs.  Water levels were further increased by the melting of a above normal snow pack in the northern Rockies.  The high water levels, plus the threat of flood waters due to the unusually high snow pack in the Rockies and additional heavy rains over the upper Missouri River Basin all contributed to record releases from the Missouri River Reservoirs. Releases from Gavins Point Dam, which is the last in the chain, increased to over 100 kcfs during the first week of June and then rose to around 160 kcfs by the middle of the month. The previous record release was 70 kcfs. The high levels of releases produced flooding which gradually worsened from May into June and then continued through July and into August.

Flood in HARRISON, IOWA
From 01-JUN-11 00:00:00 to 30-JUN-11 23:59:00 (CST-6)
Location: RIVER SIOUX
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 brought widespread flooding along the River. The river near Blair started June around 28 feet, flood stage is 26.5 feet, and gradually climbed to a little under 33 feet by the end of the month.  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 were noted.  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.   Flooding along the Missouri continued through July and into August.

Flood in MONONA, IOWA
From 01-JUN-11 00:00:00 to 30-JUN-11 23:59:00 (CST-6)
Location: ALBATON
Flood cause: Heavy Rain / Snow Melt
Property damage: 20.00K
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 brought widespread flooding along the River. In Monona county the flooding generally began during the first week of the month as the gauge at Decatur didn't surpass flood stage until around June 6th. 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 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 the month 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 July.

Flood in POTTAWATTAMIE, IOWA
From 01-JUN-11 00:00:00 to 30-JUN-11 23:59:00 (CST-6)
Location: GRABLE
Flood cause: Heavy Rain / Snow Melt
Property damage: 200.00K
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 brought widespread flooding along the River. The river near Omaha climbed to around its 29 foot flood stage late in May, and then continued rising to a little under 36 feet by the end of June.  The flooding in Pottawattamie county closed several parks and recreation areas and flooded parking lots and parts of the parking garage of 2 riverboat casinos. Some roads along the river also flooded including 16 miles of Interstate 29 north of Council Bluffs.  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.  The flooding persisted into July.

Flood in MILLS, IOWA
From 01-JUN-11 00:00:00 to 30-JUN-11 23:59:00 (CST-6)
Location: FOLSOM
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 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.  The flooding affected marshes and farmland along the river and a few roads and recreational areas were also flooded.  The water treatment plant and wellheads near Glenwood were sandbagged to prevent flood waters from reaching them.  By the middle of June about 125 of the 500 residences along the river had left their dwellings.  The flooding persisted into July.

Flood in FREMONT, IOWA
From 01-JUN-11 00:00:00 to 30-JUN-11 23:59:00 (CST-6)
Location: BARTLETT
Flood cause: Heavy Rain / Snow Melt
Property damage: 500.00K
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, which climbed above its 18 foot flood stage in mid April, started June around 23 feet and then began rising by the 10th eventually reaching a record crest a little over 28 feet by the end of the month.  The river stayed well above flood stage into July. A levee west and southwest of Hamburg experienced seepage in several areas prompting partial evacuation of Hamburg on the 5th.  The levee eventually failed by the middle of June causing extensive flooding of farmland, roads and a few highways near Hamburg, including 10 miles of Interstate 29.  Highway 2 that led into Nebraska City was also closed by the middle of June due to flood waters.  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 town kept much of the flood waters out of Hamburg during June.  Around 600 people in Percival, Bartlett and Paul were evacuated toward the end of the month and on June 30th the levee near Percival failed causing additional flooding and closing of more of Interstate 29.