Flood Zones and Missouri River Flood Risk in Harrison County, Iowa

2011: a levee breach north of Council Bluffs reaches into Harrison County

The summer of 2011 brought historic Missouri River flooding, driven by heavy upstream snowmelt and rainfall managed through the river's reservoir system -- flooding considered one of the costliest in the Missouri River's history, causing five deaths and flooding more than 4,000 homes region-wide. In Harrison County specifically, a levee breach north of Council Bluffs on June 25 flooded part of the county, threatened to cut U.S. Route 30 between Blair, Nebraska and Missouri Valley, and inundated the DeSoto National Wildlife Refuge, an 8,300-acre refuge that straddles the Iowa-Nebraska state line along the county's western edge.

2019: a levee fails at Missouri Valley itself

Less than eight years later, Harrison County flooded again -- and this time the levee failure was at Missouri Valley, the county's largest city and its commercial and residential center, forcing resident evacuations in March 2019. The broader regional disaster that produced it breached or overtopped roughly 200 miles of levees across Iowa, Nebraska, Kansas, and Missouri, brought more than $2 billion in agricultural damage, and affected more than 460 businesses regionally. Crucially, the 2019 flood brought water to areas that had never flooded before -- meaning a parcel's clean flood history through 2011 was not, on its own, a reliable predictor of its 2019 exposure.

The same 2019 event hit Harrison County from a second direction, too: the Boyer River, which flows southwest across the county before joining the Missouri, crested above 25 feet and closed U.S. Route 30 near Woodbine, well east of the Missouri River bottomland itself. Regional interstate closures during the same event affected stretches of I-29 and I-680 near Crescent, Minden, Missouri Valley, and Council Bluffs. Taken together, the 2011 and 2019 events show that Harrison County's flood exposure isn't confined to a narrow strip along the Missouri River -- both the river itself and its tributary, the Boyer, have produced real flood damage here within the same generation.

What to verify before buying a Harrison County parcel

• A specific parcel's FEMA flood zone designation and any post-2019 remapping, through the Iowa Flood Center's Missouri River Flood Information System (MRFIS) and FEMA's own flood maps -- 2019 inundated areas that had not previously been mapped as flood-prone.
• Whether the parcel falls within Harrison County's F-1 Floodplain District under the county's 1996 zoning ordinance, and what floodplain development permit requirements apply, directly with the Environmental Health, Planning & Zoning department ((712) 644-2302).
• Whether a parcel sits within or depends on a specific levee (including the levee system breached in 2011 and failed at Missouri Valley in 2019) or a drainage district along the Boyer or Soldier Rivers, and that infrastructure's current condition, with the Harrison County Engineer's office.
• Flood insurance availability and cost for a specific parcel, which can be materially affected by proximity to the Missouri River or Boyer River, levee protection status, and any recent remapping.
• A parcel's own damage record from the 2011 breach or the 2019 Missouri Valley levee failure -- ask the seller directly and check county records -- since either event could have triggered an elevation, floodproofing, or buyout requirement that still attaches to the property.