July 5th, 2024. Five and a half Inches (140mm) of rain fell over the Manawa City Dam, a small, gated dam in Waupaca County, WI. The speed of the event saw the right abutment overtopped that subsequently failed through erosion. Unofficial data from Manawa shows rainfall of 4.12 inches (105mm) in 1 hour with 1.69 inches (43 mm) in 20 minutes. The timeline provided at the post event public meeting by the City of Manawa advises the gate openings were set on forecast rain of around 1.25 inches, that morning. The flood wave inundated homes and impacted the functioning pf the wastewater treatment plant. Post even issues include public safety, sightseeing management and exposure to bacteria from sediment. Manawa City has around 1400 inhabitants. The impoundment held 1078 acre feet or 1329ML, at full supply.
Wisconsin Dam Failure
Hazard driver: Rainfall
Sectors
Community Safety
Dams
Major events
Event type
Flash Flood
Thunderstorms
Learnings
Risk Appetite
Continuity Planning