Item: PERFORMANCE OF THE KITCHENER PATH PROTECTION BERM DURING THE HISTORIC JULY 2022 AVALANCHE CYCLE, SOUTHERN ALPS, NEW ZEALAND
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Title: PERFORMANCE OF THE KITCHENER PATH PROTECTION BERM DURING THE HISTORIC JULY 2022 AVALANCHE CYCLE, SOUTHERN ALPS, NEW ZEALAND
Proceedings: International Snow Science Workshop Proceedings 2023, Bend, Oregon
Authors:
- Aubrey Miller [ National School of Surveying and Mountain Research Centre, University of Otago, Dunedin New Zealand ]
- Alan Jones [ Dynamic Avalanche Consulting Ltd, Revelstoke, BC, Canada ]
- Mike Smallwood [ Dynamic Avalanche Consulting Ltd, Revelstoke, BC, Canada ]
- Don Bogie [ Department of Conservation (retired), Christchurch, New Zealand ]
- Pascal Sirguey [ National School of Surveying and Mountain Research Centre, University of Otago, Dunedin New Zealand ]
- Todd Redpath [ National School of Surveying and Mountain Research Centre, University of Otago, Dunedin New Zealand ] [ School of Geography, University of Otago, Dunedin, New Zealand ]
- Perry Bartelt [ WSL Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland ] [ Climate Change, Extremes and Natural Hazards in Alpine Regions Research Center CERC, Davos Dorf, Switzerland ]
Date: 2023-10-08
Abstract: An extreme mid-winter rain event generated the largest avalanche cycle seen in decades in the central Southern Alps of Aotearoa New Zealand. The record-breaking 18-19 July 2022 storm brought over 500 mm of rain to an above-average snowpack, initiating a widespread mass movement cycle that included snow avalanches, debris flows and significant rain runoff causing localized flooding. The event offers insight into the performance of a diversion berm in the Kitchener Path, constructed in 2018, which was designed to mitigate the hazard to the settlement of Aoraki/Mount Cook Village from a 1:100-year dense flowing avalanche. The berm performed as designed, deflecting the main avalanche (Size 4.5) with only minor overtopping. A post-event UAV survey combined with a 2 m pre-event digital surface model allowed for the estimation of the deposition volume (approximately 175,000 m3) after considerable erosion from further rain in the runout zone. The lower 40 m of the berm was eroded by runoff from the >300 mm of rain that fell after the first avalanche, creating a channel up to 4 m deep in the toe of the debris. Dynamic modelling characterizes the flowing conditions, including the frontal velocity and impact pressures as the first avalanche entered the runout zone and contacted the berm. The event offers insight into both the design of protection structures when faced with extreme mid-winter rain, as well as how to think about more frequent extreme rain in the future.
Object ID: ISSW2023_P2.34.pdf
Language of Article: English
Presenter(s): Mike Smallwood
Keywords: diversion berm, hazard mitigation, extreme rain, rain-on-snow, RAMMS, New Zealand
Page Number(s): 846 - 853
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