01/08/2007 Council Packet - Laserfiche WebLink

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Anoka County Multi -- Jurisdictional All Hazards Mitigation Plan Blaine experienced severe thunderstorms in 1987, 1991 and 2002. In 1987 the Police Department fleet of squad cars sustained $74,000 in damage from large hail. Downed trees and roof damage was the major impact of these storms. Damage amounts are unknown, but estimated in the $500,000 range per major storm event. The likelihood of occurrence of these storms is high due to Blaine's climate and geographic location. Thunderstorms are a frequent occurrence for the City of Blaine. With Blaine's rate of growth and construction practices what they are, loss from future severe thunder storms would be more significant than what has been seen historically. Burns Township, Centerville, Circle Pines, Columbia Heights, Ham Lake, Oak Grove, Spring Lake Park, St. Francis and Hilltop experienced severe Thunderstorms, hail, winds, lightening in 2001, 2004 and twice in 2005. In all cases power outages occurred resulting from downed power lines. Hundreds of trees have been destroyed by these storms. It is expected that the frequency of these storms will continue to be moderate and the impact moderate. In the 2005 severe weather event, Coon Rapids experienced hundreds of trees uprooted, power outages due to downed lines; property damage including but not limited to debris damage to private property; some roofs taken off, streets blocked by debris and downed trees; urban flooding due to heavy rainfall and catch basins clogged with debris; hail damage. In 1996, Fridley encountered over 2 Million dollars in damage from a severe storm. In 1998 another 2.2 million in damage and over 1.5 million in damage from the September 2005 storm. Ham Lake, on July 1, 1997, was impacted by a severe storm. The Fire Department responded to many calls, municipal employees worked overtime, pumping was required to stabilize a pond in one neighborhood and prevent loss of property /lives, the fire station required roof repair, and a city owned billboard required repair. Since 1961, 144 severe thunderstorms, hail, lightning, and wind have impacted Anoka County and its jurisdictions resulting in 4 fatalities and 27 injuries. In addition $15,116,306 in structure damage and $15,382,477 in content damage has been logged. Overall the frequency of future occurrences will continue and are considered moderate. The impact of these severe storms is moderate to high and as construction and population continue to increase the impact is expected to increase to high. A detailed list of severe storms is provided in Appendix A. 4.3.1.9 Severe Weather - Tornado Tornados are violent windstorms characterized by a twisting, funnel- shaped cloud. Spawned by a thunderstorm (or sometimes as a result of a hurricane), the funnel does not need to reach to the ground for a tornado to be present. A debris cloud beneath a thunderstorm is all that is needed to confirm the presence of a tornado. The damage from a tornado is a result of the high wind velocity and wind -blown debris. The intensity, path length, and width of tornadoes are rated according to a scale developed by T. Theodore Fujita and Allen D. Pearson. The Fujita- Pearson Tornado Scale is presented below. Tornadoes classified as FO -F1 are considered weak, those classified as F2 -F3 are considered strong, while those classified as F4 -F5 are considered violent. •