| Design
Above – Figure 4: Map of ice jams in the continental US. (Cold Regions Research and Engineering Laboratory website)
Frazil ice
Frazil ice (frazil) is suspended ice crystals, which form when water is slightly below the freezing temperature. These crystals can deposit on intake racks of hydropower dams and reduce flow and hydropower production. Raking the rack to remove the frazil or providing heated racks are two methods to minimize the effects of frazil.
Effects of climate change on ice jams Climate warming may shift numerous characteristics
of river ice runs including breakup time of year, ice thickness, and rain-induced breakup. Changes in precipitation, snowpack, snow melt, and wind could affect how, when, and where ice runs occur.[4] The temperature range between solid and liquid
states of ice is narrow. Small increases in temperature could dramatically affect when and which rivers experience spring ice runs. [5] Climate change uncertainty calls for consideration of conservative engineering practices for cold weather phenomena.
Operator safety Operator safety in cold regions is essential.
Improvements in operator safety can also improve the safety of the public, improve gate operations, and make power production more reliable. Dam operators in cold weather regions are exposed
to potentially hazardous winter freezing conditions, including snow, ice, wind, and sleet for extended periods. Ice can build up on walkways, handrails, powerlines, and unprotected equipment. The following strategies can be used to improve O&M staff safety in cold regions [6]
:
Avoiding inclined walkways; provide stairs instead to ascend/descend.
Heating stairs and walkways to minimise ice and snow accumulation. Pitching and draining horizontal walkways to prevent puddles from forming that could freeze and become a slip hazard to operators. For stairs, using metal stairs with open grate anti-slip metal treads and handrails on both sides. Providing roofs over operator walkways and operable mechanical electrical equipment. Providing a heated space/office at the dam to protect operators from the elements and provide storage of personal protective equipment.
Figure 7: An insulated radial gate heating system (Eagle Creek Renewable Energy)
Figure 8: Frazil ice on intake racks at this dam resulted in a 15-foot head differential. (Eagle Creek Renewable Energy)
Figure 9: Spencer Dam damage after ice jam breaks through the structure. Gate operations to pass large ice rubble were hindered by snow, ice, freezing rain, and high wind conditions. © robert2001 /
Shutterstock.com
Left, from top to bottom: Figure 5: Ice breaking structure upstream from a river dam. (Eagle Creek Renewable Energy)
Figure 6: Ice Breaking ship (US Coast Guard)
About the Author
Mark Baker, P.E. is a Senior Dam Safety Programme Engineer specialising in dam safety programme audits and human factors in the investigation of dam failures and incidents. He is principal of DamCrest Consulting located in Denver, Colorado, US.
Peer review This article was reviewed by Lee Wooten, P.E. (GEI Consultants), Ryan Schoolmeesters, P.E. (Eagle Creek Renewable Energy), and Clint Brown, P.E. (Engineering Analytics)
References
[1] U.S. Army Corps of Engineers Manual No. 1110-2- 1612 Engineering and Design - Ice Engineering.
[2] Burrell, B. C., Beltaos, S., & Turcotte, B. (2022). Effects of climate change on river-ice processes and ice jams. International Journal of River Basin Management, 21(3), 421–441.
https://doi.org/10.1080/15715124.2 021.2007936
[3] Dam Failures and Incidents (book), Baker, Association of State Dam Safety Officials (ASDSO), 2024
[4] Spencer Dam Failure Investigation Report, ASDSO, 2020
[5] Woo, M. (2019). Cryohydrology in Canada: A brief history. Hydrological Processes, 33(26), 3407– 3411.
https://doi.org/10.1002/hyp.13581
[6] Baker, M. 2021 Dams in Cold Regions Should Account for Ice, Lessons Learned,
DamFailures.org
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