1. US Army Corps of Engineers BUILDING STRONG ® Significance of Snowmelt and River Ice on Flood Damages Meredith Carr Research Hydraulic Engineer Cold Regions Research and Engineering Lab, Hanover, NH Missouri Basin River Forecaster’s Meeting 21 February 2013

2. BUILDING STRONG ® Outline  Objectives  Background  Data  Analysis  Results  Summary

3. BUILDING STRONG ® Objective  Flood Risk Reduction Mission ► Feasibility and cost benefit analysis of flood control projects ► Management of existing projects ► Development of tools and theories related to predicting and designing for cold regions flooding  Quantify the significance of snowmelt, rain-on- snow and river ice related flooding ► Property and crop damages ► Injuries/loss of life

4. BUILDING STRONG ® Background  94 million acres of land in US estimated at risk for flooding  ¾ of presidential disaster declarations associated with flooding  Annual average of $6 B damages and median of 81 lives lost (2006, 2008 studies)  Increase in flooding impact due to urbanization and coastal development

5. BUILDING STRONG ® Snowmelt Floods  Factors affecting flood severity: ► fall soil moisture condition ► ground frost ► water content of snow ► speed of melting ► presence of heavy rain  Particular concern in Northeast, north central and eastern US, also downstream in large drainage basins  8 of 32 most significant floods of 20 th century were related to snowmelt (Perry, 2000)

6. BUILDING STRONG ® Accumulated annual snowfall divided by annual runoff. Red lines indicate areas where streamflow is snowmelt dominated (Barnett et al, 2005) Snowmelt Floods

7. BUILDING STRONG ® Snowmelt Floods Red River of the North Flood, 2009 Snowmelt flooding in the Midwest, 1993. Mississippi River, near Memphis, 2011Millington, Tennessee, May 2, 2011

8. BUILDING STRONG ® Rain on Snow Floods  Common in the Pacific Northwest, but also in other areas  Rain provides energy to melt the snow, releasing water and increasing runoff Fig 4: Sites with Rain-on-Snow Events from 1949-2003 (McCabe et al., 2007) Date LocationDamages Feb-05 California$7M Dec-05 Oregon$57M Jan-09 Washington State$57M Jan-05 Utah, 6 deaths $300M

9. BUILDING STRONG ® Willamette River in flood stage, 1996 Rain-on-Snow

10. BUILDING STRONG ® Ice Jam/Action Floods  ice cover breaks into large pieces which move downriver and elevate water levels or form a jam  freezeup jams, which occur as ice forms dynamically at the onset of cold temperature, can cause long term flooding Date LocationDamages Jan-01 Youghiogheny River at Mckeesport, PA $2M May-02 Alaska Rivers$8M Mar-07 Little Minnesota River and Lake Traverse, ND$5M May-09 breakup of Kuwoskwim and Yukon Rivers$12M Mar-09 Missouri R. at Bismark, ND$92M

11. BUILDING STRONG ® Ice Jam/Action Floods Fig 7: Explosive Remnants on the Missouri River Ice Jam, March 2009 (Stromme, 2009) Skunk River near Augusta, IA, 2010 Yukon River near Eagle, AK, 2009

12. BUILDING STRONG ® Data and Analysis  Data sources (2001-2010): ► Flood events from the National Climatic Data Center Storm Events Database ► CRREL Ice Jam Database ► Snow water equivalent gridded data based on SNODAS data ► USGS gages along major snowmelt rivers ► Weather Review Journal articles

13. BUILDING STRONG ® Results  Damages due to snow and ice related flooding were most significant in Northern cold and snowy areas, but also extended to downstream areas such as the lower Mississippi River basin Fig 11: Percent of Flooding Damages Due to Snowmelt or Ice by Sub-Region

14. BUILDING STRONG ® Results  Snow and ice related flood damages, by Corps District  Most significant damages in the New England District, the Mississippi Valley Division and the Northwest Division.  Rain-on-snow events are common in the Northwest, contributing to the over 50% of flood damages due to snowmelt or ice in the Sacramento District. Fig 13: Percent of Flooding Damages Due to Snowmelt or Ice by Corps district. Blue Circles Represent Flood Control Dams

15. BUILDING STRONG ® Results Percent of Flooding Damages Due to Snowmelt or Ice

16. BUILDING STRONG ® Results Total Property and Crop Damages 2001-2010

17. BUILDING STRONG ® Results

18. BUILDING STRONG ® Results  Snow and ice related flooding ► contributed to 42% of flood events during the 10 year period ► 48% of damages, 22% of fatalities, 10% of injuries ► Event length of 3.1 d Snowmelt: 4.3 d, Ice action: 2.9 d, Ice Jams: 2.1 d, Rain-on-snow: 1.8 d Annual Economic Losses ($M)FatalitiesInjuries Average Event Length (days) Number of Events Hurricane/Coastal 169521381.8192 Tornados 28845122.1100 Snowmelt/Ice/Rain-on- Snow 1,4801402173.1376 Rainfall 1,1854127841.7 217

19. BUILDING STRONG ® …..Discussion….. Sunday, March 22, 2009 in Fargo (AP Photo/The Forum, Dave Wallis)

20. BUILDING STRONG ®

22. Tornado Jun-07 Texas$81M7 deaths May-10 Tennessee$2B10 deaths Oct-09 Arkansas$21 M Hurricane Aug-12 TS Fay, Florida and Georgia$84M Sep-04 Hurrican Ivan$375M Sep-10 TS Hermine, Texas$29M6 deaths Coastal Apr-07 New Jersey, New York, Massachusettes$48M Dec-07 Washington and Oregon$12M Sep-06 Virginia$47M Nov-09 North Carolina$6M Rain only Oct-06 Lousiana, Texas, Mississippi$620M Jul-12 Illinois, Iowa, Wisconsin$376M Jun-01 Virginia, Pennsylvania, Marlyand, Connecticut$35M