US Army Corps of EngineersBUILDING STRONG®

Significance of Snowmelt and River Ice on Flood DamagesMeredith CarrResearch Hydraulic Engineer

Cold Regions Research and Engineering Lab, Hanover, NH

Missouri Basin River Forecaster’s Meeting

21 February 2013

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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

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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

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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 20th century were related to snowmelt (Perry, 2000)

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Accumulated annual snowfall divided by annual runoff. Red lines indicate areas where streamflow is snowmelt dominated (Barnett et al, 2005)

Snowmelt Floods

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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   Location DamagesFeb-05  California $7MDec-05  Oregon $57MJan-09  Washington State $57MJan-05  Utah, 6 deaths $300M

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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   Location Damages

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

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Ice Jam/Action Floods

Fig 7: Explosive Remnants on the Missouri River Ice Jam, March 2009 (Stromme, 2009)

Skunk River near Augusta, IA, 2010Yukon River near Eagle, AK, 2009

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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

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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

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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

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Results

Percent of Flooding Damages Due to Snowmelt or Ice

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ResultsTotal Property and Crop Damages

2001-2010

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Results

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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) Fatalities Injuries

Average Event

Length(days)

Number of Events

Hurricane/Coastal 169 52 138 1.8 192

Tornados 288 45 12 2.1 100Snowmelt/Ice/Rain-on-

Snow 1,480 140 217 3.1 376

Rainfall 1,185 412 784 1.7 217

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…..Discussion…..

Sunday, March 22, 2009 in Fargo (AP Photo/The Forum, Dave Wallis)

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Tornado        Jun-07  Texas $81M 7 deaths

May-10  Tennessee $2B 10 deathsOct-09   Arkansas $21 M  

Hurricane        Aug-12  TS Fay, Florida and Georgia $84M  Sep-04  Hurrican Ivan $375M  Sep-10  TS Hermine, Texas $29M 6 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