Flash Flood — Sauk, Wisconsin

2008-06-09 · near Lake Delton, Sauk, Wisconsin

Event narrative

Sauk County experienced 4 flash flood events over a 3-day period. Two of the events started on June 7th, one on June 8th, and the last one on June 9th. In each case, flash flooding caused home and business damage as well as crop losses. Roads were blocked or washed out (STH 154 and CTH C), and bridges were damaged. Many vehicles stalled. Locations in the Baraboo River Valley sustained considerable damage as the river crested at all-time levels. Collectively, each of these 4 flash floods resulted in home and business damage along with some crop losses. It was nearly impossible to break down the damages by flash flood event. Therefore, the collective breakdown is provided in the June 9th StormData entry for Sauk County.

On June 9th, the levee holding back Lake Delton eroded over a 5 hour periiod and eventually broke (the actual dam held), allowing Lake Delton to empty into the Wisconsin River. A 300-foot section of CTH near the breach was washed away. At least 4 homes were washed away, and damage was inflicted on boats and piers. There were no injuries or fatalities.

The breakdown for residential home losses for the 3-day period were: over 800 minimally affected, 45 with major damage, and 31 destroyed (total of $19.2 million for home losses). Business losses are estimated to be about $1 million. Crop losses were estimated at $15 million. Public sector damage was about $2.25 million. Several roads and bridges sustained damage.

Wider weather episode

A slow-moving surface boundary, nearly parallel with the mid-level flow affected southern Wisconsin during the period of June 7th through June 9th. A strengthening low-level jet and strong moisture advection produced several rounds of thunderstorms during the period in the vicinity of this boundary. The atmosphere was very moist with precipitable water values around 2 inches. Low to mid-level wind flow supported training of flood-producing thunderstorms. There was sufficient vertical wind shear to allow for supercell development that resulted in 10 tornadoes spinning up in south-central and southeast Wisconsin on June 7th. A weak cool front pushed through southern Wisconsin late on the 8th/early on the 9th, finally ending the heavy rainfall.

The heavy rain axis for June 7-9th ran from Sauk County southeast to Milwaukee County, where generally 6 to 9 inches fell on a ground that was totally saturated due to record-setting winter snowfalls and a wet April, 2008. Several locations topped 10 inches, and Watertown (Jefferson Co.) came in with 13.5 inches, 11.35 inches was measured in Oak Creek (Milwaukee Co.), and Elm Grove in Waukesha County picked up 10.8 inches.

The Baraboo River crested at all-time record-high levels at the following gauge sites: La Valle (23.23' on 6/10), Rock Springs (28.73' on 6/11), West Baraboo (27.48' on 6/12), and Baraboo (27.48' on 6/13). Elsewhere, new all-time crest levels were establised at Franklin on the Root River (11.0' on 6/8), near Raymond on the Root Canal River (12.12' on 6/9), and at Racine on the Racine River (11.29' on 6/9).

View location on OpenStreetMap → (43.5902, -89.7659)

Source: NOAA Storm Events Database, event_id 113225. Narrative written by the NWS forecast office that issued the report.