Flash Flood — Waukesha, Wisconsin

1997-06-21 · near Menomonee Falls, Waukesha, Wisconsin

Wider weather episode

Flash flooding occurred primarily in eastern Waukesha county as a result of heavy rainfall amounts in excess of 5 to over 8 inches in a 30 hour period ending about 1000CST. This flash flooding was greater than a "100 year rainfall" based on rainfall frequency maps. No one was injured or killed by the flood waters, thanks to superb rescue efforts by local law enforcement officials and firefighters. Besides public sector damage in county/city parks, there was private and business damages. The hardest hit area was the city of Menomonee Falls, followed by New Berlin, Lannon, Sussex, and the town of Lisbon. Spotty flash flooding was noted in the cities of Oconomowoc, Hartland, Delafield, and Pewaukee. (On July 7th, Waukesha county was officially declared a Federal Disaster Area, making county residents and business owners eligible for Federal disaster aid).Areas along and near the Menomonee River experienced moderate to major flooding to nearby roads, homes, and businesses. In Menomonee Falls, several homes had significant structural damage, while about a total of 50 homes and basements had significant loss of personal property. Some car dealerships and repair shops suffered damage to new and used vehicles. Hundreds of homes and businesses lost their electrical, natural gas, or telephone service. Many traffic lights were also inoperative. Several roads and underpasses across the eastern half of the county were flooded with several feet of water, resulting in road closures. Some drivers had to be rescued after their vehicles were swept away by deep, fast water currents over roads. Sections of asphalt paving were washed away on several roads in the eastern part of the county.Many farm fields in the eastern half of the county suffered soil erosion, or had enough standing water leftover to completely damage this years crops. Nearly all golf courses in the county were closed due to high water levels. A 12-foot sinkhole developed in the backyard of a Hartland residence as the ground collapsed.Rainfall totals for the 30-hour period ending 1200CST were 8.40 inches in the city of Menomonee Falls, about 6.50 inches in Sussex, 5.95 inches in Elm Grove, 5.20 inches in Pewaukee and Waukesha, 5.01 inches in Hartland, 3.90 inches in Delafield, and 2.44 inches in Oconomowoc. Due to runoff, the Fox River throughout the county rose to 1 to 2 feet above flood stage, resulting in minor to moderate flooding along the river. At some locations along this river, this would be a 5 to 10 year flood. Flood gates on dams at Pewaukee and Nagawicka Lakes were opened to lower lake levels and relieve pressure. Properties and businesses along and near these lakes sustained flooding damage. These lakes were at the highest levels ever remembered by local residents. In the southeast part of the county, a small earthen dam on Jewel Creek just north of Little Muskego Lake was in danger of failing due to high water levels and water pressure. A small portion of the dam was breeched. However, later in the day on June 21st and on the 22nd, DNR officials gradually lowered the lake in a controlled manner, to avoid any serious flooding.

Source: NOAA Storm Events Database, event_id 5608893. Narrative written by the NWS forecast office that issued the report.