Flash Flood — Cass, Iowa

1998-06-14 · near Atlantic, Cass, Iowa

Wider weather episode

A strong upper level system combined with a warm front located to the south of Iowa set the stage for a major flood event. Iowa soils were already saturated before the event took began. The severe thunderstorms mentioned above were only the beginning. They moved off to the northeast during the night as the upper level low pressure system became nearly stacked over southwest Iowa. A small cluster of thunderstorms formed over the southwest counties during the early morning hours. There was little movement and heavy rainfall ensued over Cass County. Cass County was the hardest hit as 13.18 inches of rain fell during the morning into early afternoon hours. Seven inches of it fell in a 4.5 hours period between 0830 and 1300 CST. This amount of rainfall set a state record for the greatest 24 hour rainfall total from an official site. Cass County became cut off as the flood waters rose rapidly. Entire towns were evacuated as houses were covered with water in some places. The Governor of Iowa declared the county a disaster area by evening. Flooding was not limited to Cass County. During the morning, a deformation zone formed from west central into central Iowa. Bands of heavy thunderstorms moved up from the south and became stationary in an east to west band from west central into central Iowa. Rainfall of one to two inches in less than 2 hours was common, with many areas receiving three inches or more of additional rainfall. Urban and small stream flooding was widespread with considerable ponding and lowland flooding reported. During the late afternoon and evening hours, the deformation zone shifted south and expanded as the upper low drifted off to the east. The flooding was not as bad as that experienced earlier in the day, but did set the stage for major river flooding to follow. Many areas reported river stages at record or near record highs following this event. Thoughts of the "Flood of '93" were heard around the state. In Lake Panorama area, saturated soil around the lake began to slide into the lake by late in the afternoon. Three homes began to slide with the soil and began cracking as the earth sank some 12 to 18 inches. The three houses were said to be damaged beyond repair. In the town of Atlantic, 21 houses were destroyed by flooding. As the flood crest caused by the heavy rains moved down the Raccoon River, the town of DeSoto was left without water for a few days. The water treatment plant there is located next to the river and was engulfed by floodwaters. MidAmerica Energy shut off natural gas service to the town of Atlantic as the flood waters crested as a precautionary measure. In addition to the property losses, wildlife losses were great. Millions of Pheasants, rabbits, and other ground nesting wildlife perished in the high waters. Damage to highways and secondary roads was extensive. Some of the preliminary estimates received were: $560,000 in Guthrie County, $380,000 in Audubon County, and $400,000 in Dallas County. At the time of this writing, the worst damage...which was in Cass County, was still not known.

Source: NOAA Storm Events Database, event_id 5654076. Narrative written by the NWS forecast office that issued the report.