Resolution 7478 hazard mitigation

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2024 Hennepin County All -Jurisdiction Hazard Mitigation Plan Volume 2 — Hazard Inventory Crow River reached flood stage of 10 feet on 4/4/97 at Rockford which is the river monitoring point. The river crested at 14.4 feet on 4/9/97 which was the fifth highest crest ever recorded. The river subsided to below flood stage on 4/20/97. Substantial flooding occurred at a golf course in the town of St. Michael. (NCDC Storm Events) 2001 Severe Winter Storms, Flooding, and Tornadoes (DR-1370) The Mississippi River at Fridley crested twice. First at 16.60 ft. on April 15, 2001, and second at 16.40 ft. on April 281h, 2001, 0.6 and 0.4 ft. over flood stage respectively. Four factors contributed to the flooding of 2001: significant autumn precipitation, heavy winter snowfall, less than ideal snowmelt scenario, and record -breaking April precipitation (http://cIimate.umn.edu/doc/journal/fIood_2001/flood_2001.htm). April 161h the Crow River at Rockford, MN crested at 14.5 feet with a peak discharge at 13,100 ft3/s which is 4.5 ft. over flood stage. 2010 Flooding (DR-3310) • Crow River at Rockford reached 13.99 ft. on March 22, 2010, which was 3.99 ft. over flood stage. 2014 Severe Storms, Straight -Line Winds, Flooding, Landslides and Mudslides (DR-4182) • Crow River at Rockford crested at 15.08 ft. on June 251h, 2014, which was 5.08 over flood stage. 4.2.2.8. Future Trends Ble Changes in river flooding can be caused by changes in atmospheric conditions, land use/land cover, and water management. These changes can occur in tandem, or individually which makes it difficult to determine which factor acts as the driving force of changes in river flooding behavior. However, long-term data does show and increase in flooding in the norther half of the eastern prairies and parts of the Midwest. Even with data showing days with heavy precipitation increasing, this trend does not strongly relate to changes, or increases, in river flooding. One conclusion for this is the mismatch of seasons with which the high precipitation events occur and most likely season for flooding in most river basins within our region$. For example, the northern Great Plains typically sees peak river flooding during spring snowmelt, however, generally the heaviest daily rainfall events occur during the summer. When considering the issue of future river flood hazard changes, it is important to recognize that urban and rural land -use impacts, and water management have significant influence on river flood behavior. While precipitation and flooding have been increasing in the northern half of the eastern prairies, general circulation models do not show this as an area expected to have a substantial increase in runoff in the twentieth-century or the twenty-first century forecast. 4.2.2.9. Indications and Forecasting River Flooding typically occurs hours to days after a high precipitation event. Warnings for river floods can often provide much more lead-time that those for flash flooding. 4.2.2.10. Detection & Warning 41