Computational Procedure (Population Distribution)

Population distribution is based on the procedures outlined in the HAZUS-MH 2.1 Earthquake Model Technical Manual, Tables 3.26 and 3.27, following the logic from Table 13.2 (Appendix A, Section A.1). The computational procedure for the population distribution is described below:

1. Generate census block population by a HAZUS damage category for night (2:00 a.m.) and day (2:00 p.m.) conditions. To do that, HEC-FIA:
   
   
   1. Obtains census block population from the HAZUS hzDemographicsB table for the HAZUS demographics categories.
      
      
   2. Computes census block population for night and day conditions by HAZUS occupancy type.
      
      

2.  Compute the number of households per census block. This computation uses information from the HAZUS demographic categories, the number of structures from the structure inventory, and the following formula:

   $$//<![CDATA[ \begin{array}{l}\displaystyle NumberHouseholds = (households per structure) * (Number of structures)\end{array} //]]>$$

3. Distribute population based on time of day
   

1. 1. Calculate total population during the day from the hzDemographicsB table in the HAZUS database using the formula:

      $$//<![CDATA[ \begin{array}{l}\displaystyle PopulationDay = residday + 0.98*workingcom + hotel + 0.80*schoolenrollmentkto12 + schoolenrollmentcollege + 0.80*workingind + 0.80*visitor\end{array} //]]>$$

   2. Calculate total population during the night using the formula below:

      $$//<![CDATA[ \begin{array}{l}\displaystyle PopulationNight = residnight + 0.02*workingcom + 0.10*workingind + hotel\end{array} //]]>$$

   3. Calculate the population per household (day) using the formula below:

      $$//<![CDATA[ \begin{array}{l}\displaystyle PopHouseholdDay = PopulationDay / (Number of households_day)\end{array} //]]>$$

   4. Calculate the population per household (night) using the formula below:

      $$//<![CDATA[ \begin{array}{l}\displaystyle PopHouseholdNight = PopulationNight / (Number of households_night)\end{array} //]]>$$

   5. Distribute population to each structure based on households per occupancy type and the population per household day and night.
      
      
      

   6. Determine a percentage reduction to the population for both over and under the age of 65 using the following formula:

      $$//<![CDATA[ \begin{array}{l}\displaystyle PercentOver65 = (malesOver65 + femalesOver65)/(total population)\end{array} //]]>$$

   7. Apply the percentage reduction to the population for individuals over 65 (from the equation in step 3f) and use the PopulationDay and PopulationNight calculated values per structure (from the equations in steps 3a and 3b, respectively), to determine the over 65 day and night population per structure in the two equations below:

      $$//<![CDATA[ \begin{array}{l}\displaystyle Over65PopDay = (PopulationDay) * (PercentOver65) Over65PopNight = (PopulationNight) * (PercentOver65)\end{array} //]]>$$

   8. Calculate the under 65 day and night population values using the PopulationDay and PopulationNight calculated values per structure (from the equations in steps 3a and 3b, respectively), and the over 65 day and night population per structure (from the equations in step 3g), to determine the under 65 day and night population values at each structure ( (in the two equations below):

      $$//<![CDATA[ \begin{array}{l}\displaystyle Under65PopDay = PopulationDay - (Over65PopDay) Under65PopNight = PopulationNight - (Over65PopNight)\end{array} //]]>$$