Economic data consists of the data needed to translate the hazard into dollar-denominated consequences in the floodplain: a structure inventory and occupancy type data. This data makes up the exposure and vulnerability pieces of the consequences equation.  Aggregated stage-damage functions represent consequences and are computed by tying the structure inventory and occupancy type data to the hydraulic modeling. 

Occupancy Types

Occupancy type data includes information that is general to a particular class of structures, such as residential structures with one floor and no basement. The purpose of occupancy type data is to help link the structure inventory to the hazard, describe the vulnerability to the exposed assets, and reflect the uncertainty in consequence calculations. 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 (review the HEC-FDA user manual References). Other occupancy type data must be developed locally, including uncertainty parameters and content-to-structure value ratios. 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 (review the HEC-FDA user manual References).

Occupancy Type Data

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.
  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.

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

Instructional Videos

Please review the short instructional video for more information on importing and working with occupancy types in HEC-FDA Version 2.0.

Adding Occupancy Type Data

This instructional video provides a brief overview of the required and optional data and two options for adding occupancy type data, manual entry and tab-delimited importing. The "Adding Occupancy Type Data" video also includes a brief exploration of the Occupancy Types editor.

Working with Occupancy Type Data

This instructional video gives a brief explanation of what occupancy types are and how they are used in HEC-FDA Version 2.0. The "Working with Occupancy Type Data" video also highlights some important concepts regarding HEC-FDA Version 2.0. Topics covered in this video include the following:

  • Brief review of flood risk with regards to the consequences side of the risk equation and how occupancy types are used to describe the vulnerability of assets at risk.
  • How depth-percent damage functions and structure characteristics (like the elevation of the first finished floor) in HEC-FDA is used to represent a structures vulnerability (susceptibility to harm) for three generic structures.
  • Brief overview of the options for defining uncertainty.
  • Vehicle only occupancy types.

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 of 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.

Structure Inventories

A structure inventory is a data set that consists of observations on the structures in the floodplain. A structure inventory is needed to calculate the consequences - in dollar-denominated terms - of flooding for the range of possible flood events. Modern approaches for putting together a structure inventory include the National Structure Inventory and/or the use of publicly-available data such as county tax records and Google Earth. Below is an image of a structure inventory for Muncie, Indiana taken from the National Structure Inventory. The attributes of the structure, such as structure type and location, have been refined by reviewing Google Maps and Google Maps Street View imagery and editing the attribute table with geospatial software.

Working with Structure Inventories in HEC-FDA

HEC-FDA accepts point shapefile structure inventories only. The points in the shapefile represent the structure locations. Modifications to the structure inventory (e.g., to reflect non-structural actions) should be imported as distinct point shapefiles instead of the use of modules. The required attributes for each structure include:

  • Structure ID
  • Dollar-denominated structure value
  • Occupancy type
  • First-floor elevation or ground elevation and foundation height

Upon import, you need to select whether the first floor elevation or the ground elevation and foundation height will be used. If ground elevation and foundation height are selected, you will need to identify the source of ground elevation (structure inventory or terrain file). Optional attributes include:

  • Beginning damage depth
  • Content value
  • Other value
  • Year in service
  • Number of structures
  • Metadata/notes

Differences Between HEC-FDA Versions 1 and 2

  1. HEC-FDA Version 2.0 does not handle flat file structure inventories (i.e., tab-delimited text files). A structure inventory must be in the form of a point shapefile. 
  2. Structure modules will not be used in HEC-FDA Version 2.0. To reflect differences in structure inventories between project conditions or analysis years, import separate structure inventories. Only one structure inventory will be used for a given stage-damage compute, so each imported structure inventory should contain all structures required for a given project condition - analysis year combination. 
  3. Stage-direct damage functions were entered into study data as part of the structure inventory in HEC-FDA Versions 1. In HEC-FDA Versions 2, a stage-direct damage function is entered into study data as a manually-entered stage-damage function. 

Steps to Import a Structure Inventory

  1. Right click on Structure Inventories under Economics within the Study Tree and select Import from Shapefile.
  2. Give the imported inventory a useful name and description.
  3. Identify the path of the shapefile.
  4. Select first floor elevation or ground elevation and foundation height.
    1. If ground elevation and foundation height, select source of ground elevation.
  5. Identify required attributes and any optional attributes.
  6. Click next, select source of occupancy types, and match imported occupancy types to occupancy types in the structure inventory.
  7. Click Finish.

Instructional Video

Please review the short instructional video for more information on importing Structure Inventories in HEC-FDA Version 2.0. The instructional video provides a brief overview of the required and optional study data and steps for importing a structure dataset. The video also gives a conceptualized overview of the role structures play when "HEC-FDA assesses flood risk" (review the HEC-FDA user manual's Flood Risk Assessment and HEC-FDA page for more information).

Aggregated Stage-Damage Functions

An aggregated stage-damage function is the relationship between the stage at the location of the hydrologic and hydraulic input relationships and the coinciding level of damage in the floodplain. The aggregated stage-damage function is aggregated at the impact area-damage category-asset category level for a given set of hydraulics modeling and H&H input functions (e.g. flow-frequency and stage-flow or just stage-frequency). The purpose of an aggregated stage-damage function is to reflect the consequences piece of the risk equation. When an aggregated stage-damage function is linked to a stage-frequency function, we get a damage-frequency function, the relationship that is integrated to calculate expected annual damage. An aggregated stage-damage function with uncertainty is computed within HEC-FDA using the structure inventory, a set of hydraulic profiles, and H&H input functions (flow-frequency and stage-flow or just stage-frequency). Alternatively, for unique situations, an aggregated stage-damage relationship may be manually entered.

Working with aggregated stage-damage relationships in HEC-FDA

Typically, you will compute aggregated stage-damage relationships in HEC-FDA. You will need to have imported a set of hydraulics and a structure inventory as well as have defined for each impact area the flow-frequency and stage-flow functions or just stage-frequency function to compute the aggregated stage-damage relationships. Take a look at the following video to learn more about computing aggregated stage-damage relationships in HEC-FDA.

Differences Between HEC-FDA Versions 1 and 2

  • In HEC-FDA Version 1.4.3, stage-direct damage functions were entered into study data through the structure inventory, and were saved, imported from/exported to tab delimited within the occupancy types. In HEC-FDA Version 2.0, a stage-direct damage function for a particular structure should be entered into a study using a manually-entered stage-damage function. The best way to track the structure of interest as it relates to its stage-direct damage function is to assign the structure to its own damage category. Stage-direct damage functions will not import into HEC-FDA Version 2.0 from HEC-FDA Version 1.4.3 - they will have to be manually entered. When using HEC-FDA Version 2.0 to compute stage-damage functions, create and manually enter a dedicated damage category for each structure that uses a stage-direct damage function and manually edit the function as needed. 
  • Index points are no longer required for a stage-damage compute. The aggregation stages are identified using the H&H input functions. 

Steps to Compute Aggregated Stage-Damage Relationships

  1. Right-click on Stage-Damage Relationships under Economics within the Study Tree and select Create New Aggregated Stage-Damage Relationship.
  2. Define a useful name and description.
  3. Select Computed.
  4. Optionally, enter the Analysis Year. Analysis Year must be entered correctly if Year In Construction will be used in the structure inventory.
  5. Select the H&H input functions for each impact area, a hydraulics data set, and a structure inventory. 
  6. Optionally, select Write Details to CSV to obtain structure-level stage-damage details (Version 2.0 provides the same information found in Version 1.4.3 Fda_StructDetail.out).
  7. Click Compute Curves, Save, and Close. See below for image of finished Aggregated Stage-Damage Functions.

Instructional Video

Please review the short instructional video for more information on importing creating aggregated stage-damage functions in HEC-FDA Version 2.0. The instructional video provides a brief overview of the required and optional study data and steps for creating and computing aggregated stage-damage functions. The video also gives a conceptualized overview of the role structures play when "HEC-FDA assesses flood risk" (review the HEC-FDA user manual's Flood Risk Assessment and HEC-FDA page for more information).

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