Flood — Polk, Iowa

2008-06-10 to 2008-06-20 · near Johnston, Polk, Iowa

Wider weather episode

Heavy rainfall continued across the state into the second week of June. The rain of the first week set the stage, heavy rain going into the second week put things over the top. Much of the damage in terms of heavy rain occurred during the 24 hour severe event of the 7th and 8th of the month. With all of the wet weather during the month, Iowa recorded an exceptionally small range of temperatures during June. Daytime highs reached into the 90's on only three dates (7th, 8th and 25th) with a statewide maximum of 92 recorded on the 7th at Onawa and Little Sioux. A lower June maximum temperature has not been recorded since 1928. Meanwhile the month's lowest temperatures were 45 readings at Cresco on the 2nd and at Chariton and Cresco on the 17th. A higher June minimum temperature has not been recorded since 1932. The overall monthly range in extreme temperatures was only 47, the smallest June temperature range on record (previous record was a 51 range in 1932, from 48 to 99). The first half of June averaged 2.1 warmer than normal and it appeared that Iowa would break its string of six consecutive colder than normal months. However, the second half of the month averaged 2.2 cooler than normal, allowing the cold weather streak to extend to seven consecutive months. Iowa endured an exceptionally wet period from May 29 through June 12 when a statewide average of 8.99 inches of rain fell (normal for the period is 2.45 inches). Daily statewide average rain statistics are not available very far back in time but it is doubtful that a larger amount of rain has been recorded in Iowa in only 15 days. Record flooding occurred along the entire length of the Cedar River, the Iowa River below Marshalltown, the Mississippi River along Louisa and Des Moines counties and a portion of the Des Moines River between Fort Dodge and Des Moines. Many other smaller rivers and streams also recorded major or record flooding. The most exceptional flooding occurred at Cedar Rapids where the Cedar River crested on June 13 at 19.12 feet above flood stage and 11.12 feet higher than the previous record crests recorded in 1929 and 1851. Monthly precipitation totals reported thus far vary from 3.35 inches at Sioux City (0.26 inches below normal) to 15.05 inches at Massena and 15.13 inches at Dorchester (10.42 inches above normal). It is expected that higher totals occurred but have yet to be reported. The flooding was described as a 500 year flood, Iowa's second in the past 15 years. During the summer there was a considerable amount of discussion as to whether these valued needed to be changed. The flooding was so severe that Governor Chet Culver declared 86 of the 99 counties in Iowa as State Disaster areas. In the Des Moines CWA, only Emmet, Calhoun, and Sac Counties were not included in the declaration. Federal Disaster declarations were issued by FEMA for much of the state as well with 80 of Iowa's 99 counties receiving the Federal Declaration. In the Des Moines CWA, only the counties of Emmet, Calhoun, Sac, Audubon, Clarke, Wayne, and Winnebago were left out. The flooding was the most severe over the northeast half of the CWA. Property damage was significant and will likely exceed $1 billion, though the final total will not be known for at least 1 to 2 years by the time all of the claims are filed. Crop damages were incredible. Statewide damage will likely be in the neighborhood of $4 billion. During mid June, 2.5 to 3 million acres of corn and soybeans were under water. Though some of it may be replanted, the state agricultural department estimated that there was no chance of replanting at least 1 million acres of land in low areas. At the end of June, the heavy rain and flooding had taken its toll on the crop with only about half of the crop reported in good to excellent conditions, the remainder was fair, poor, or very poor. Yield will likely be done significantly over the entire state. True totals will not be known until harvest this fall. Based on what actually occurred during the summer of 1993, these estimates will likely be in the ball park or even a little low. The Iowa Department of Agriculture and Land Stewardship reported that damages to water conservations structures was round $40,000,000. An estimated 2.3 million acres, or about 10% of Iowas cropland, had severe soil erosion, which is defined as 20 or more tons of soil loss per acre. Flooding was major in many cities and towns in the state. One of the more incredible occurrences was in Mason City. The Winnebago River actually changed course during the flooding and flash flooding. The city was completely inundated and the city water supply was out for several days. Reports from the state indicated that 125 miles of primary highway in Iowa was washed out by the flooding. Flooding forced the closure of 464 miles of Iowa's primary highway system and 303 bridges and culverts. Nearly 1500 miles of roads were in need of replacement following the floods. Preliminary damage estimates for road infrastructure was $80,000,000. The state's rail office had counted 17 railroad bridges and several hundred miles of track damaged or destroyed by the flood waters. Railroad damage was estimated in the $68 to $83 million range and it was expected to take 6 to 12 months to repair the damage. Governor Chet Culver estimated that damage across the state was nearly $10 billion, making it the worst disaster ever to occur in the state of Iowa.

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Source: NOAA Storm Events Database, event_id 105711. Narrative written by the NWS forecast office that issued the report.