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<br />Ramsey County | Multi-Jurisdiction Hazard Mitigation Plan 25 <br />• Inundation maps <br />• Appendices <br />Dam failure is the collapse or failure of an impoundment that causes significant downstream flooding. <br />The principal consequences of dam failure are injury, loss of life, and significant downstream property <br />damage. The energy of water stored behind even a small dam is capable of causing loss of life and great <br />property damage to people living downstream. The collapse or structural failure of a dam may be <br />caused by severe storm, earthquake, improper maintenance, erosion, or acts of terrorism. A failure in a <br />dam upstream can cause additional strain and failure risk to dams further downstream. The Battle Creek <br />dams are the only dams located within Ramsey County that are classified as High and have developed <br />EAPs for review. The Coon Rapids Dam and the St. Anthony Falls Upper and Lower Locks and Dams are <br />classified as significant and have also written EAPs. <br />3.5.4 HISTORY <br />There have been no dam failures in Ramsey County in the past, though there have been a number of <br />dam failures within the State of Minnesota. Most reported failures have been in low hazard dams, with <br />at least one exception; the Thomson Dam in northeastern Minnesota overtopped in 2012 due to heavy <br />rains, causing significant damage to its hydroelectric station and contributing to flooding downstream. <br />There have been no known deaths, injuries, or property damage from dam or levee failures in the <br />County. The effects on life and property in the area could be significant if a dam were to fail because of <br />the nature of the built environment underneath it. <br />3.5.5 PROBABILITY <br />The probability of a specific dam failing in any given year is extremely low. Some common causes of dam <br />failures include overtopping, foundation defects, cracking, inadequate maintenance, or piping and <br />seepage. According to the Association of State Dam Safety Officials, the primary cause of reported dam <br />failures between 2010 – 2019 was overtopping, most often due to flooding events. <br />3.5.6 CLIMATE CHANGE IMPACTS <br />Climate change can significantly affect the risk and severity of dam and levee failures. The changes most <br />likely to impact Ramsey County are: <br />• Changes in seasonal patterns and increased precipitation intensity – more frequent and intense <br />rainfall events or earlier spring snowmelt can result in higher risk of flooding, putting additional <br />stress on dams and levees. According to the Minnesota Department of Natural Resources <br />Climate Change Information website, heavy rains are now more common in Minnesota and <br />more intense than at any time on record. Climate projections indicate these big rains will <br />continue increasing into the future. <br />• Increased extreme weather events – more frequent and severe storms can cause a higher risk <br />for dam or levee overtopping. <br />• Temperature changes, including increased freeze-thaw cycles – this could impact the integrity of <br />dam and levee foundations. <br />• Increased demand on water resources – increased demand has the potential for more frequent <br />drawdowns of reservoirs and added stress on dam operations and structures.