1. Ten Most Costly Floods
In US History

2. 1927 Mississippi River
Date: April-May 1927 
Area or Stream With Flooding: Mississippi River from Missouri to Louisiana 
Reported Deaths: Unknown 
Approximate Costs: $2.89 Billion 
Cause: Heavy rain and failed levees In the summer of 1926, heavy rain soaked the Mississippi River Basin, causing it and and its tributaries to swell and break through the levee system in several states. The flood covered 27,000 square miles in ten different states. At the peak of the flood, 14% of the state of Arkansas was under the river. Then-Secretary of Commerce Herbert Hoover came into national prominence because of the disaster and later rode this fame to the presidency.

3. 1964 PNW Floods
Date: December 1964-January 1965 
Area or Stream With Flooding: Pacific Northwest 
Reported Deaths: 47 
Approximate Costs: $3.02 Billion 
Cause: Melting snow and heavy rain Heavy snows covered the Western Cascade mountains in Oregon in December Mid-month, the area was hit with unseasonably warm temperatures that melted the snow while nearly a foot of rain fell over the region in just a few days. The heavy waters coming down from the mountains flooded a vast region of the state of Oregon, including the entire town of Salem, which was submerged under nearly 10 feet of water.

4. 1913 Ohio Flood
Date: March-April 1913 
Area or Stream With Flooding: Ohio, statewide 
Reported Deaths: 467 
Approximate Costs: $3.25 Billion 
Cause: Heavy rainfall Excessive rainfall in March 1913 caused water systems all over the state, particularly the Great Miami River, to flood their banks. No major part of the state was spared. The disaster killed 467 people and damaged more than 40,000 homes. Dayton's main street was submerged by ten feet of rapidly moving water

5. 1996 Willamette Valley Flood
Date: December 1996-January 1997 
Area or Stream With Flooding: Pacific Northwest and Montana 
Reported Deaths: 36 
Approximate Costs: $3.47 billion 
Cause: Melting snow and heavy rain Steady rain, rather than snow, raised the water table significantly through January. After several feet of snow blanketed the area, a quick temperature shift filled the rivers with new water that flooded into Idaho, Washington, and California. Roughly 30,000 residents were forced to flee.

6. 1965 South Platte River
Date: June 1965 
Area or Stream With Flooding: South Platte/Arkansas Rivers in Colorado
Reported Deaths: 24 
Approximate Costs: $3.94 billion 
Cause: Extremely heavy rain in a short period of time 
Unprecedented rainfall levels of more than a foot in a single night caused the South Platte River to become a massive flash flood of 15-foot water sweeping through the riverbed from Littleton, Colorado, all the way north to the border of Nebraska. All 26 bridges in the path of the raging river were ripped to shreds and carried away.

7. Date:January-March 1995 
Area or Stream With Flooding: California 
Reported Deaths: 27 
Approximate Costs: $4.29 Billion 
Cause: Frequent heavy storms An "El Nino" storm dumped as much as 20 inches of rainfall on parts of California in a few days as the Napa River set a new peak record. Two years later, the state would suffer another similarly catastrophic flood resulting from tropical storm rainfall.

8. The 1936 New England Flood
Date: March 1936

Area or Stream With Flooding: New England 
Reported Deaths: 150+ 
Approximate Costs: $4.72 Billion 
Cause: Heavy rain, ice jams, destruction of dam 
 During the winter of 1935, heavy snowfall and low temperatures caused a dense snow pack to accumulate across northern New England. In mid-March, temperatures quickly warmed as heavy rain began to fall across Maine and New Hampshire. As a result, massive flooding and ice jams occurred throughout the region, ripping off a 1,000 foot section of the top of the Holyoke Dam. The entire Connecticut River flooded New Hampshire and Maine.

9. The 1951 Kansas Flood
Date: July 1951

Area or Stream With Flooding: Kansas and Neosho River Basin in Kansas 
Reported Deaths: 15 
Approximate Costs: $6.71 Billion
 
Cause: Heavy rain over long duration 
In the summer of 1951, nearly a straight month of heavy rains fell on eastern Kansas and Missouri, flooding the banks of the Kansas and Neosho River basins. By the time the water subsided, roughly 2 million acres were flooded -- the equivalent of half of New Jersey being underwater. More than 500,000 people were displaced.

10. The 1995 Louisiana Flood
Date:May 1995 
Area or Stream With Flooding: South-central United States
 
Reported Deaths: 32 
Approximate Costs: $7.87 Billion 
Cause: Multiple heavy thunderstorms 
 In May, southern Louisiana received some of the heaviest rainfall in recorded history, with 23 inches falling in two days. New Orleans, which itself received more than 20 inches of rain, incurred more than $350 million in damages. Before Hurricane Katrina, it was the worst flood in 100 years.

11. The (forgotten) Great Missouri Flood of 1993
Date: May-September 1993 
Area or Stream With Flooding: Mississippi River Basin in Central United States
 
Reported Deaths: 48 
Approximate Costs: $30.2 Billion 
Cause: Long period of heavy rain The most destructive flood in the history of the United States affected almost the entire Midwest, across 20 million acres -- a portion of land roughly the size of the state of South Carolina.[Pictured: the rivers to the north of St. Louis under normal conditions, on top, and in 1993.]