Category: Dams

6 July 2024

Wisconsin Dam Failure

July 5th, 2024. Five and a half Inches (140mm) of rain fell over the Manawa City Mill Pond, a gated small 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, and 1.1 inches in 10 minutes within an event total of 5.5 inches (140mm). 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 dam operator was back on site by 11am and witnessed the dam overtopping. The embankment failed completely around 1pm. Impacts included flooded homes and impacts to the functioning of the wastewater treatment plant. Manawa City has around 1400 inhabitants. The impoundment was 192 acres (0.77km2) with a max depth of 12 feet (3.65 metres).

25 June 2024

Minnesota Partial Dam Failure

June 25th, 2024. Southern Minnesota. Rapidan Dam partially failed with water eroding the left abutment during a flood event . The dam was built in 1910 for hydroelectricity by impounding the Blue Earth River, but ceased energy production in 2019 following flood damage. Ice damage also occurred in 2020. The 87 ft (26.5 metres) high dam dam has a catchment of 2430 square miles, or 6239 Km2.

23 June 2024

Swiss Flash Floods and Intense Rainfall

June 21st, 2024. Switzerland. Rainfall led to significant flash flood impacts in the Moesa River valley in Switzerland. Official totals show around 100mm of rain within 1 hour around Grono, with unofficial data showing 15mm in five minutes ending at 19:35 at one site. Landslides resulted in fatalities. Part of the A13 road was undermined by erosion. The discharge at Lumino increased from 214m3/s to 594 m3/s in 30 minutes from 19:45, according to Swiss Govt flood warning data. The catchment area to Lumino is 472km2.

29 April 2024

Kenya Rail Embankment Failure

April 28th 2024. According to The Nation, Heavy rains in the Rift Valley led to build up of water behind a rail embankment and blocked culvert in Mai Mahiu. The embankment subsequently failed with a flash flood impacting downstream villages and leading to 48 fatalities. Initial reports of the failure of a nearby dam were incorrect. Learnings relate to risk around unplanned storage of water and culvert sizing.

1 March 2024

Whakaari White Island Judgement

The sentencing and judgement into the Whakaari White Island eruption contains learnings on the application of monitoring and managing natural hazard risk in so far as reasonably practicable. (SFARP). Key learnings relate to training, communication and systems testing.

1 March 2022

Enoggera Dam – Unusual Loading

March 1st, 2022. Brisbane. The Enoggera Reservoir peak lake level of 81.39mAHD in February 2022, had a flood loading just shy of 1:10000 Annual Exceedance Probability (AEP) (1:10000 AEP level listed as 81.4mAHD) according to the approved Emergency Action Plan. Rainfall frequency assessments for the catchment indicate the 2022 event was between a 1:200 and 1:500 AEP representing a discrepancy between the flood frequency and rainfall frequency.