What is Occupancy Type Data?

Occupancy type data includes information that is general to a particular class of structures, such as residential structures with one floor and no basement.

What is the Purpose of Occupancy Type Data?

Occupancy type data is used to help link the structure inventory to the hazard, describe the vulnerability to the exposed assets, and reflect the uncertainty in consequence calculations.

Where Do I Get Occupancy Type Data?

Some occupancy type data is national in scope, such as the generic depth-percent damage functions found in Economic Guidance Memorandums 01-03, 04-01, and 09-04 (References). Other occupancy type data must be developed locally, including uncertainty parameters and content-to-structure value ratios. Many studies have already developed regionally specific occupancy type data, and economists are encouraged to seek these out if appropriate for current and new studies. 

Tab-delimited text files exported from HEC-FDA Version 1.4.3 are properly formatted for importing occupancy type data into HEC-FDA Version 2.0. For importing occupancy type data from a tab-delimited text file, review the HEC-FDA Version 1.4.1 User's Manual, Appendix D, to view the requirements for the tab-delimited text file (References).

Working with Occupancy Types in HEC-FDA

Occupancy types may be imported into HEC-FDA as a text file, and must be imported before importing a structure inventory. The format of the text file matches the format used by HEC-FDA Version 1. See the HEC-FDA Version 1.4.1 User's Manual, Appendix D for more information about formatting occupancy type data in the tab-delimited format.

Required Data

The required occupancy type data include:

  • Name and description
  • Structure depth-percent damage function with uncertainty

Depth-percent Validation

Please be aware that the software will validate the specified distribution of percent damage on the depth-percent damage functions to be between 0% and 100%, inclusive. However, some distributions of percent damage in the EGM curves have non-negligible ranges outside the valid range of percent damage. In that case, the cells with the offending values will be highlighted red. However, the aggregated stage-damage compute will still run successfully because HEC-FDA will force realizations of the depth-percent damage function to be monotonically increasing. If you're using depth-percent damage curves that match the EGM, you can ignore this validation. 

Optional Data

Optional (but highly suggested) data include:

  • Content, other, and/or vehicle depth-percent damage functions with uncertainty
  • Either uncertainty about content, other, and/or value, or content- and/or other-to-structure value ratios with uncertainty
  • Uncertainty about the first floor elevation (or foundation height, assuming zero uncertainty in terrain data)
  • Uncertainty about structure value

Asset Categories

Asset category is a new term to the HEC-FDA software but not a new concept. Asset category encompasses structure, content, vehicle, and other - four types of damage that may be associated with a particular asset in the inventory. At this time, data on the structure asset category must be configured for a given occupancy type. If you do not wish to calculate structure damage but you would like to calculate other types of damage (e.g., if the point in the inventory represents an automobile only), there are two options for a workaround. The default behavior for an automobile in the inventory (i.e., an asset in the inventory with a damage category of AUTO) is to use structure damage and not vehicle damage. Alternatively, set structure value for the asset to zero, use arbitrary data for the structure damage parameters for the relevant occupancy type, and use relevant data for the asset category parameters of interest.  

Differences Between HEC-FDA Versions 1 and 2

  1. There is a difference in HEC-FDA Version 2 when defining distributions about the content and other-to-value ratios. In HEC-FDA Version 1, the standard deviation, min, or max of the content (or other)-to-structure value ratio is given as a percent of the ratio, whereas HEC-FDA Version 2 directly uses the standard deviation, min, or max. In HEC-FDA Version 1 for example, for a content-to-structure value ratio of 50%, an entered standard deviation of 10% would mean that the plus or minus one standard deviation range is 45% to 55%. In HEC-FDA Version 2, the standard deviation would be entered as 5% to obtain the same range. Importing data into HEC-FDA Version 2 from HEC-FDA Version 1 corrects for this difference. 
  2. Uncertainty in HEC-FDA Version 1 could be defined about content-to-structure value ratio but not about content value in the case that content value is contained within the structure inventory (rather than being estimated using the content-to-structure value ratio). In HEC-FDA Version 2, uncertainty can be defined for either approach used. 
  3. Multiple groups of occupancy types are allowed. The group-occupancy type assignment is made upon import of a structure inventory. 

Steps to Import Occupancy Types

  1. Right-click on Occupancy Types under Economics within the Study Tree and select Import Occupancy Types.
    Tab-Delimited Text File Import Shortcut Menu Command
  2. Identify the occupancy types text file path and click the Import button to import the occupancy types. If desired, customize the occupancy types name.
    Tab-Delimited Text File Importer and Import Log

If desired, occupancy types can be manually entered. See the section on the HEC-FDA User Interface for an exploration of the Occupancy Types editor. 

Specifying Uncertainty Distributions

Several occupancy type parameters may be defined with uncertainty. Information on specifying uncertainty distributions about these parameters is provided below. 

  1. Structure, content, other, and vehicle uncertainty parameters 
    1. Normal distribution: coefficient of variation (standard deviation as percent of the mean).
    2. Log normal distribution: same as normal distribution, except that the mean and standard deviation reflect logged data, so the coefficient of variation reflects the standard deviation of logs divided by the mean of logs. Structure values should not be in log units. 
    3. Triangular distribution: minimum percent of the inventoried object (structure, content, other, or vehicle) value and maximum percent above the inventoried object value. 
    4. Uniform distribution: minimum percent of the inventoried object value and maximum percent of the inventoried object value. The inventoried object value is not explicitly used in the specification of the uniform distribution. 
  2. First floor elevation uncertainty parameters 
    1. Normal distribution: standard deviation of the first floor elevation distribution, in the same unit of measurement as that which is used to measure the first floor elevation (e.g., feet).
    2. Log normal distribution: same as normal distribution, except that the mean and standard deviation reflect logged data. 
    3. Triangular distribution: minimum and maximum in the same unit of measurement as that which is used to measure the first floor elevation. The minimum and maximum are specified relative to the most likely value - that is, their distance from the most likely value. The most likely value is the value in the structure inventory. For example, a given occupancy type may be defined with a triangular distribution about the first floor elevation where the minimum is 1 foot below the most likely value and the maximum is 1.5 feet above the most likely value. The minimum is then entered into HEC-FDA as 1, the maximum is entered as 1.5. Then, if the inventoried first floor elevation of a structure with the given occupancy type is 3 feet, then the distribution of first floor elevations is triangular where the minimum is 2 feet, the most likely is 3 feet, and the maximum is 4.5 feet. 
    4. Uniform distribution: similar to the triangular distribution, except the inventoried value is used only for indexing and is not explicitly used in specifying the distribution. For example, the minimum may be defined as 1 foot and the maximum as 1.5 feet. A structure with that occupancy type and a first floor elevation of 3 feet then has a uniform distribution about the first floor elevation with a minimum of 2 feet and a maximum of 4.5 feet.
  3. Content-to-structure value ratio and other-to-structure value ratio 
    1. Normal distribution: mean and standard deviation of the ratio. 
    2. Log normal distribution: same as normal distribution, except that the mean and standard deviation reflect logged data. 
    3. Triangular distribution: minimum, most likely, and maximum values of the ratio.
    4. Uniform distribution: minimum and maximum values of the ratio.