Estimating Flood Damage Impacts on Existing and Future by yaofenji

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									     Estimating Flood Damage Impacts on
     Existing and Future Development
     Within the Poudre River Flood Floodplain in
     Fort Collins, Colorado



      22nd CASFM Conference
      September 2011, Snowmass, CO

Jeff Brislawn, CFM - AMEC
Brian Varrella, CFM – City of Fort Collins
Presentation overview



 Poudre River Damage Assessment Project Background
 Hazus-MH overview
 Data needs
 Proposed development analysis
 Loss Estimates Results
 Hazus and Damage Estimation Limitations




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Background and Need



 The Poudre River floodplain in Fort Collins contains areas that some
    consider prime for development
   City Council initiated review of level of floodplain regulations as part of
    a Stormwater Repurposing effort
   Council initiated a study to examine the economic ramifications of
    floodplain development restrictions
   City Stormwater Utility Staff needed to quantify the flood damage
    potential to existing and proposed development and the public safety
    risks
   Both studies were presented at a Council work session to allow
    informed decision making on floodplain regulation options




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Poudre River Floodplain Regulation Options Considered



 Option #1:     The Poudre River floodplain regulations be revised to
    adopt a 0.1 foot rise floodway
      More restrictive
   Option #2: The Poudre River floodplain regulations be revised to not
    allow any structures in the 100-year floodplain
      Most restrictive
   Option #3: No change to the Poudre River floodplain regulations (null
    alternative)
      No residential development in 100 year
      Commercial development floodproofed 2ft above base flood elevation
       – No rise in floodway
     Least restrictive
   Option: #4 – No Adverse Impact


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Poudre River Flood Threat



 Poudre is the largest watershed in the City
 Drains 1,537 square miles of land into Fort Collins
 Generates a peak flow of 13,300 cfs and velocities over 13 fps
 Can flood for days or weeks vs. hours in other basins
 Floods can be caused by rain, snowmelt, and rain-on-snow storm
    events
   Further development in the floodplain results in increased risk to
    existing properties
   Allowing more development in the floodplain puts additional people
    and property, including emergency response personnel, at risk
   Reducing risk through construction projects not viable: Only viable
    approach is to manage risk through floodplain regulations and
    property acquisitions


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Flood Damage Analysis Scope of Work


 Conduct a flood damage analysis to determine impacts of flooding on
    existing and proposed development on four study areas.
      HAZUS-MH - FEMA’s GIS-based natural hazard loss estimation
       tool was used to perform a flood loss estimation for existing
       development in the study areas
      Estimate flood impacts to proposed development based on
       development projections with a focus on flood disruption losses,
       with estimation based on accepted methods and values.
         –Assess public safety impacts
   Results presented at City Council work session in February 2011




                                                                          6
Study Area Overview



 Four localized study areas
 Align with areas of interest
  in separate economic
  development/impact study
 149 structures total
 Development primarily
  commercial but some
  residential mixed in




                                 7
Hazus MH Overview



 Hazus-MH = Hazards U.S. Multi-Hazard
 FEMA’s GIS-based loss estimation software for earthquake, flood and
    hurricane disasters
   Couples engineering and hazard science with GIS
   Estimate physical damage, economic loss, social impacts
   Free – provided you have an ESRI ArcGIS license
   Data options: Default (Level 1) or user defined (Level 2)




                                                                        8
Hazus Model Output


                                      Earthquake           Flood            Hurricane Wind
                                      Ground Shaking    Frequency Depth
                                                                            Pressure | Missile | Rain
                                      Ground Failure   Discharge Velocity
     Direct Physical Damage
        General Building Stock                                                       
          Essential Facilities                                                       
     High Potential Loss Facilities                                                   
       Transportation Systems                                
           Utility Systems                                   
     Induced Physical Damage
           Fire Following       
     Hazardous Materials Release                                                      
          Debris Generation                                                          
     Direct Economic/Social Losses
      Building Replacement Cost                                                      
             Income Loss                                                             
            Crop Damage                                       
             Casualties                                Generic Output
            Shelter Needs                                                            
     Indirect Losses
            Production                                       
              Income                                         
           Employment                                        
      Impacts With/Without Aid                               




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Modifying Hazus with user-supplied data:
Building Inventory


 Site specific building information provided by City GIS and
  County assessor
 Key Data fields needed for Hazus:
   Occupancy type, structure & contents values, type & year of
    construction, number of stories, basement presence
 56 of 149 structures had missing or incomplete attributes
   Assumptions made based on data & image interpretation
 Hazus tools to upgrade building inventory data
   Comprehensive Database Management System (CDMS)
     –Aggregates data to Census Block level; essential facilities
       data site specific
   User Defined Facility tool for site specific analysis

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Modifying Hazus with user-supplied data:
Flood Hazard data


 Hazus enables import of user-
  supplied flood depth information
 Ayres Associates developed
  detailed depth grids based on
  recent DFIRM studies
    10 year (10% annual chance) flood
    50 year (2% annual chance) flood
    100 year (1% annual chance) flood




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Hazus Loss Estimation



 Based on the depth grid, Hazus uses average depth at
  each structure location to estimate damage based on
  depth-damage functions
 Depth damage functions used
   Commercial, average retail (U.S. Army Corps of Engineers)
   Residential, one floor - no basement (Flood Insurance
    Administration)
   Residential, one floor - with basement (Flood Insurance
    Administration)
   Residential, mobile home (Flood Insurance Administration)




                                                                12
Losses Estimated – Existing structures



 Building and content damages
     Contents estimated @ 50% of structure value for residential, 100% of value
      for commercial based on FEMA standards.
 Capital-related income losses of lost services and sales, business
    disruption
   Displacement costs for temporary relocation
   Rental income loss to building owners
   Debris generation
   Displaced population
      Based on average household size multiplied by the number of residential
      structures impacted
 Average Annualized losses

                                                                                   13
Study Area 1



N College and Vine
Avenues – North
College Urban
Renewal Area




                     14
Study Area 2 – Link-N-Green Golf Course




                                          15
Study Area 3 – Lemay and Mulberry St




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Study Area 4



Prospect Avenue

WW Reynolds
Office Park




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Hazus Limitations



 HAZUS limitations discovered
   User Defined Facilities tool did not work properly; workaround
    developed using Comprehensive Data Management System
    essential facility import tool.
   MR4 & MR5, known bug: does not apply user-specified damage
    curves, uses default curves instead
   Where damage curves were not properly applied, damages were
    calculated using spreadsheet method




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   Loss Estimates – Existing Development

              Building    Contents       Income-           Total           Displaced   Debris
Return Period Damage      Damage         Related Loss      Damage          Population* Generated
                                           Study Area 1
100-year Flood   $ 513,017 $ 1,001,272    $       23,000   $   1,537,289          15.1    29 tons
50-year Flood    $ 371,016 $ 661,771      $       15,000   $   1,047,787          12.6    19 tons
10-year Flood    $ 200,644 $ 262,583      $        7,000   $     470,227          12.6     7 tons
                                           Study Area 2
100-year Flood   $ 350,491 $ 1,038,074    $        8,000   $   1,396,565             0         0
50-year Flood    $ 295,737 $ 863,163      $        3,000   $   1,161,901             0         0
10-year Flood    $ 35,129 $ 101,967       $          -     $     137,096             0         0
                                           Study Area 3
100-year Flood   $ 423,655 $ 1,221,743    $          -     $   1,645,398          52.9     3 tons
50-year Flood    $ 212,357 $ 622,519      $          -     $     834,876          10.1     3 tons
10-year Flood    $ 113,503 $ 333,916      -                $     447,419           0.0          -
                                           Study Area 4
100-year Flood   $   2,965 $    10,656    $       23,000   $     36,621              0     9 tons
50-year Flood    $   2,865 $    10,056    $        1,000   $     13,921              0          -
10-year Flood    $     -   $       -     -                 $        -   -                       -


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Estimating Losses to Proposed Development

      Key question: What is the residual risk when areas are developed
              according to local floodplain management regulations?
   Public Safety impacts
      Risk to employees, customers
      Emergency services time, resources, and personnel risks
       – Evacuation and rescue costs
 Economic Losses
     Capital-related income loss*
       – Loss of services/sales*
       – Loss of wages*
       – Loss of sales tax*
    Displacement costs*
 Physical damages
    Debris removal costs*
    Vehicles, parking lots, utilities and infrastructure
* Can be quantified
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Losses Estimated – Proposed Development



 Capital-related income losses of lost services and sales due to
    restricted business access, sales tax reductions
   Displacement costs for temporary relocation, business disruption
   Rental income loss to building owners
   Debris removal costs




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Estimating Flood Displacement Costs -
FEMA Standard Values




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Proposed Development Analysis Key Assumptions


 Proposed development building occupancy and square footage was
    obtained from a separate Economic Impact Analysis to ensure
    consistency in development assumptions
      Assumed all proposed building within the floodplain
   Assumed new or substantially-improved development will conform to
    existing floodplain regulations and limit/reduce losses.
   Assumed a two day disruption period for the 100 year flood, based on
    Corp hydrology study
   Disruption costs – One time disruption costs based on Hazus
    standard values
   Rental income losses based on Hazus standard values for retail
   Capital income loss – average daily sales based on estimated retail
    sales from Economic Impact Analysis
   Sales tax reductions – estimated by applying sales tax rate to capital
    income loss
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Flood Damage Analysis –
Existing and Future Development




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Loss Estimation Summary



    $4.5 million estimated loss to existing development across the four
    study areas for 100 year flood
   $1.78 million in flood disruption costs to proposed development under
    the “no change” option
    $6.4 million combined losses
   $1.1 Million average annualized losses to existing development

     Annualized Loss
     Study Area 1  $ 397,189
     Study Area 2  $ 350,423
     Study Area 3  $ 380,600
     Study Area 4  $   6,570




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Limitations – Losses Not Included



 Proposed development analysis only estimated 100-Year event
  losses
    Did not estimate potential losses from floods greater than or less than the
     100-Year event
 Did not include difficult to quantify losses such as:
    Casualties (injuries or deaths)
    Emergency services time/resources and risk, evacuation and rescue costs,
     cleanup costs
    Parking lot damage, landscaping damage, vehicle damages, equipment or
     materials stored outside
    Utility damages (sewer, water), road repair, bridge repair




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Public Safety Considerations



 The Economic Impact and Flood Damage Analyses showed
    approximately an additional 1,500 to 4,000 employees in the 100-Year
    floodplain assuming maximum development
      Based on an estimate of 4 employees per 1,000 sq feet of
      commercial/retail development and 3 employees per 1,000 sq feet of office
      development
 Approximately 884 employees currently within the floodplain based on
    existing commercial development square footage.
   The Flood Damage Analysis existing and future damages do not
    include estimates for
      Casualties and injuries to employees, customers, emergency services
      workers




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Conclusions and Lessons Learned



 Existing properties in the Poudre floodplain are already at risk and if
    current development practices continue in the 100-Year Floodplain
    life-safety risks and property damages will increase unless regulations
    become more stringent
   Losses would be shared by the City, individuals and businesses
   City Council recognized and concurred with public safety concerns
   Council felt public safety impacts and other losses were not
    emphasized enough
       Approach was too conservative
       Wanted more losses estimated
       Past events (Spring Creek Flood) should have been used to emphasize
      potential for future losses
 Hazus is a valuable tool for site specific analysis can be problematic

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Rocky Mountain Hazus User Group


 The Rocky Mountain HUG has been established to support HAZUS users across the
  Rocky Mountain Region. Conference calls and meetings are held to share resources,
   facilitate ideas and technical issues, form relationships and build a user community.



    Quarterly Conference Calls
         Always cover latest Hazus software updates/issues, announcements,
          trainings
         QA/QC of Hazus Level 1 analysis, Hazus Conference Lessons Learned,
          Dam Breach Analysis project using Hazus


                        http://www.usehazus.com/rmhug/




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Questions?



Jeff Brislawn
AMEC
303-820-4654
jeff.brislawn@amec.com

Brian Varrella
City of Fort Collins
970-416-2217
bvarrella@fcgov.com




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