2009 Flood - Red River Basin Commission by wuzhenguang

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									IDENTIFYING WHAT WE DIDN’T KNOW



 Development of Technical Data
             For
  Long Term Flood Solutions
           For the
       Red River Basin

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                            LTFS
                          Study Area

                          • U.S. Portion of
                          Red River Basin
                          (MN, ND & SD)

                          • Main Stem
                          Red River

                          • Tributaries


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Items Needed for Development of Plan


• Level of Protection Goals
• Consistent mapping and data
• Understanding Floods Along Red
  River
• Existing Projects
• Potential Flood Damages
• Effectiveness of Alternatives
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                            Winnipeg

                          • Earliest documents of
                          flooding go back to 1798

                          •Largest flood
                          documented was 1826.
                          Peak flow was estimated
                          about 225,000 cfs, about
                          40% greater than in 1997

                          • Winnipeg Floodway
                          was expanded in 2010 to
                          handle 140,000 cfs and
                          safely pass about 700
                          year flood through
                          Winnipeg



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         Level of Protection Goals

• Establish “Level of Flood Protection” goals to use
    as “Guideline” to achieve Flood Resiliency
•    Major Urban areas and critical infrastructure –
    500 year flood or greater
•    Cities – 200 flood year or greater
•    Rural residences/farmsteads – 100 year flood or
    greater
•    Use “flood of record” as goal if it is larger than the
    “guideline frequency” event

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Consistent Mapping & Data Compilation

 • Develop maps for basin that shown
   similar data and information for all
   watersheds
 • Economic and other data should be
   compiled to be comparable between
   states and watersheds
 • Evaluation of alternatives will focus on
   Red River main stem, but consider effects
   along tributaries wherever possible
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                          Maps




                             Uniform Basin
                              Maps for all
                              Watersheds

                             - Streams
                             - Existing Flood
                             Storage
                             - USGS Gages

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                          Runoff Models


                          • HEC-HMS Runoff
                          Models for subbasins

                          • Same criteria for all
                          subbasins

                          • Use LiDAR data

                          • Travel times

                          • Non-contributing
                          areas

                          • Can be used to
                          estimate effectiveness
                          of retention sites

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Understanding Red River Floods

• Basic factors related to a spring or
  summer event (water content, etc.)

• Timing of Flows from tributary subbasins

• Characteristics of each subbasin

• Effects of existing flood storage

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Every Flood is Different




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                  Antecedent Conditions
                   1997 & 2009 Floods
Winter Snowfall                             Water Content
     1997                                       2009




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     Rainfall Events – 1975 & 2002

July 1975                          June 2002




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                      2009 Flood - Fargo

                          • White Rock Dam – no flow
                          contributed to Fargo peak

                          • Ottertail River/Orwell had
                          small effect at Fargo

                          • Drainage area upstream
                          of Wahpeton/Breckenridge
                          had major contribution to
                          Fargo peak

                          • Wild Rice River upstream
                          of Abercrombie had major
                          contribution to Fargo peak

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                      2009 Flood - Fargo

                          •White Rock Dam – no flow
                          contributed to Fargo peak

                          • Drainage area upstream of
                          Wahpeton/Breckenridge had
                          major contribution to Fargo peak

                          •Drainage area along Red River
                          between Wahpeton/Breckenridge
                          and Fargo had major contribution
                          to Fargo peak

                          • Wild Rice River upstream of
                          Abercrombie had major
                          contribution to Fargo peak


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                          1997 Flood - Fargo

                          • Releases from White Rock Dam
                          did affect Fargo peak; This was
                          only flood where this has occurred

                          • Drainage area upstream of
                          Wahpeton/Breckenridge
                          contributed to Fargo peak

                          • Drainage area along Red River
                          between Wahpeton/Breckenridge
                          and Fargo was not a major
                          contributor to Fargo peak

                          •Wild Rice River upstream of
                          Abercrombie was major contributor
                          to Fargo peak

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                          2009 Flood - Halstad

                          •   Peak flows from the Sheyenne
                              River occurred several weeks
                              after peak at Halstad; not major
                              contributor to Halstad peak.
                          •   Maple River had 2 peaks; first
                              peak contributed to Halstad
                              peak
                          •   Maple River Dam reduced the
                              Maple River’s contribution to
                              the Halstad peak
                          •   First peak from Maple River
                              that contributed to Halstad
                              peak was mainly from the
                              drainage area downstream of
                              Maple River Dam

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                          2009 Flood - Emerson




                          • The flood peak from
                          Fargo/Moorhead
                          continued downstream
                          to Emerson

                          • This was generally
                          consistent with other
                          large floods for which
                          data is available



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 Elevation – Flow Relationships
Red River: Wahpeton to Emerson
                     Elevation        Change in Flow for 1 Ft
                   - W/B = 960        of Stage Increase at 100
                   - F/M = 900        Year Flood Flow Range
                   - Hal = 860       - W/B =      2,000 cfs
                   - GF = 825        - F/M =      5,000 cfs
                   - Oslo = 810      - Hal =     10,000 cfs
                   - Emer = 780      - GF/EGF= 10,000 cfs
                                     - Oslo =    30,000 cfs
                                     - Emer = 50,000 cfs




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Analysis of Different Periods of Flow Records




•Baseline through 1997 flood is currently in use • Shorter wet period increases flows at Fargo,
by most agencies (Red)                           but decreases flows for large events at Grand
• Updating through 2009 flood increases flows Forks (Green)
for various frequency events (Blue)              • Changes larger at Fargo; smaller at Grand
                                                 Forks

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Existing Flood Risk Reduction Projects

 • Compile data on existing projects from
   Federal and state agencies and cities and
   watershed districts

 • Local protection: Permanent projects;
   levels of protection

 • Flood storage projects

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Summary of Pertinent Information by City
             Grafton, ND




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                               Flood
                            Insurance
                          Policies Issued
                          • Policies increased in 1997
                          due to forecast flooding

                          • Policies in Moorhead
                          increased in 2009, 2010 &
                          2011 due to forecast
                          flooding

                          • Policies at Warren
                          dropped off after levee &
                          diversion project completed

                          • Policies at EGF in
                          “required zone” dropped off
                          after levee project
                          completed

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   Existing Permanent Flood Risk
         Reduction Projects

• Red River Main Stem
  – 9 of 22 Cities w/ 100 yr or greater protection
  – Only 2 meet “Level of Protection” goals
• MN Tributaries
  – 5 of 40 Cities w/ 100 yr or greater protection
• ND Tributaries
  – 7 of 37 Cities w/ 100 yr or greater protection
  – Only 1 meets “Level of Protection” goals

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Flood Storage Built in Basin 1909 to 2010


                                          • Total Existing Flood
                                          Storage = 1.9 Million Ac-Ft

                                          • About 75% by Federal
                                          Agencies with non-Federal
                                          partners

                                          • Much of early storage
                                          was dual-use, with flood
                                          storage obtained by
                                          winter/spring drawdown of
                                          pool



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    Flood Storage Built – 1960 to 2010

1960-79 = 132,000 ac-ft   1980-99 = 132,000 ac-ft      2000-10 = 156,000 ac-ft




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      Potential Flood Damages

• Urban
  – Corps Data indexed to 2010/2011 Price Levels
• Agricultural
  – Agency Data for 1975, 1979, 2002 & other floods
• Rural Farmsteads & Residences
  – Corps 2011 inventory plus other agency data
• Transportation
  – Agency information
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                                    Urban Damages
                                    100 Year Flood

                                    • Potential Flood Damages
$6.3                                – assumes flood fight
                                    actions are not successful

                                    •Baseline Hydrology – thru
                          $3.6      1997 Flood
       $2.7                         • Damages Prevented by
                                    Existing Flood Storage
                                    Projects = $2.2 Billion

                                    • Damages Prevented by
                                    Existing Local Protection
                                    Projects = $1.4 Billion

                                    • Potential Remaining
                                    Flood Damages = $2.7
                                    Billion

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Potential Urban Damages – 100 Year Flood
        Existing Conditions (2011)


          $2.7 Billion




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$11.4                                Urban Damages
                                     200 Year Flood
                               •Potential Flood Damages –
                               assumes flood fight actions are not
    $6.2
                               successful
             $5.2
                               •Baseline Hydrology – thru 1997
                               Flood

                               • Damages Prevented by Existing
                               Flood Storage Projects = $3.2
                               Billion

                               • Damages Prevented by Existing
                               Local Protection Projects = $2.0
                               Billion

                               • Potential Remaining Flood
                               Damages = $6.2 Billion
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Potential Urban Damages – 200 Year Flood
        Existing Conditions (2011)


           $6.2 Billion




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Potential Urban Damages – 500 Year Flood
        Existing Conditions (2011)

           $10.9 Billion




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Sensitivity of Flood Damages to Hydrology
 Baseline (1997) vs. Wet Cycle (1942-2009)

100 yr: $2.7 to $3.8   200 yr: $6.2 to $7.8                500 yr: $10.9 to $13.5


                                                                             $13.5

                                                                     $10.9

                                                          $7.8
                                                   $6.2
                              $3.8
                       $2.7




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   Agricultural Flood Damages

• Acres Flooded
  – 10 year flood = 550,000 acres
  – 50 year flood = 1.1 million acres
  – 100 year flood = 1.4 million acres
• Damages Greatest due to Summer Flood
  – 1975 summer flood about $1 Billion
• Summer Floods affect Tributaries more
  than Red River main stem

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           1997 Flooded Area


                  • Red River main stem -
                  Grand Forks to International
                  Border

                  • Very wide floodplain

                  • Widest part of Red River
                  floodplain in the U.S. part of
                  basin

                  • Generally from 6 to 10
                  miles wide



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       Rural Residences & Farmsteads


•     Detailed inventory along Red River
    from Abercrombie to Drayton

    – 2,400 Residential Structures

    – 6, 200 Farm Building
       • Includes barns, grain bins,machine sheds, etc.



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        Components of LTFS Plan

• Projects to be Implemented by Cities, Watershed
  Districts, and States & Federal Agencies
• Non-structural Measures
    –   Continued floodplain regulation and buyouts

•   Local Protection Measures
    –   Levees, floodwalls and diversions at about 40 communities
• Upstream Flood Storage
    –  1.5 Million acre-feet of storage at “appropriate/effective”
      locations
    – Distributed throughout subbasins
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 Effectiveness of Alternatives

• Red River Main Stem ( MN & ND)
      (Effectiveness on tributaries difficult to measure at this stage as it
      is very dependent on amount & location of flood storage)

• Combination of LTFS Local Measures &
  Upstream Flood Retention Storage
  – 18 of 22 Cities w/ 100 year or greater protection

  –     9 Cities meet “Level of Protection” goals


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Potential Flood Damages Preventable by
          Projects in LTFS Plan

                                                   $12.8


                                           $10.2

                                   $7.8
                        $6.3

          $4.0
   $2.8




    100 Year               200 Year          500 Year

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Existing Flood Storage in Red River Basin




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