What is an Alternative?

An alternative reflects a project condition and connects the results of two impact area scenarios for two analysis years and a given project condition.

What is the Purpose of an Alternative?

The purpose of an alternative is to collect the results necessary to compute average annual equivalent damage (formerly known as equivalent annual damage). Results include the distribution of average annual equivalent damage results, average annual equivalent damage results by damage category and by impact area.

Working with Alternatives in HEC-FDA

Differences Between HEC-FDA Versions 1 and 2

An alternative reflects the project condition dimension in HEC-FDA Version 2. An alternative is a new concept in the HEC-FDA software, though not a new concept in planning, and is closely associated with the Plan in HEC-FDA Version 1. For example, the without-project alternative reflects the information contained in the blue highlighted row in the image of the HEC-FDA Version 1 user interface below. The results of a given alternative are the same as computing equivalent annual damage analysis for a given plan in HEC-FDA Version 1. The discount rate and period of analysis are set in the study properties under the File menu. The discount rate should be provided in decimal form, not percentage. 

Steps for Specifying Alternatives in HEC-FDA

  1. Navigate to Properties under the File menu and set the discount rate and period of analysis. Please note that the discount rate should be in decimal form, not percentage.
  2. Right click on Alternatives within the Study Tree and select Create New Alternative
  3. Give the alternative a useful name and description
  4. Select the two impact area scenarios that represent a given project condition, one for each analysis year. Note: you must be sure that the period of analysis in the Study Properties is consistent with the base and future years you select.
  5. Hit Save and Close.
  6. Right-click on the alternative within the Study Tree and select View Results to compute.
  7. Select from three options in the dropdown box: Damage with Uncertainty, Damage by Impact Area, or Damage by Damage Category. 
  8. Select the level of aggregation of interest. See Alternative Results for more information.