Aggregated Stage-Damage Functions
What is an Aggregated Stage-Damage Function?
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).
What is the Purpose of an Aggregated Stage-Damage Function?
An aggregated stage-damage function reflects 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.
Where Do I Get an Aggregated Stage-Damage Function?
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.
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
- Right-click on Stage-Damage Relationships under Economics within the Study Tree and select Create New Aggregated Stage-Damage Relationship.
- Define a useful name and description.
- Select Computed.
- Optionally, enter the Analysis Year. Analysis Year must be entered correctly if Year In Construction will be used in the structure inventory.
- Select the H&H input functions for each impact area, a hydraulics data set, and a structure inventory.
- Optionally, select Write Details to CSV to obtain structure-level stage-damage details (the information found in Version 1.4.3 Fda_StructDetail.out).
- Click Compute Curves, Save, and Close. See below for image of finished Aggregated Stage-Damage Functions.