2.0 Data Requirements for a New HEC-FDA Study

Study data requirements vary widely. The requirements depend on the purpose of the study, the size of the study area, the hydrologic and hydraulic conditions of the study area, and the types of alternative plans considered, just to name a few. In general, the data required to build a new study must contain:

1. Impact areas in the form of a polygon shapefile. The file must have a string or integer field that identifies a unique name. Only one set of impact areas can be imported.  
2. Analysis year(s).

Further, for a given alternative, analysis year, and impact area, a study must contain at a minimum the following data:

1. Frequency functions - either (a) or (b) below: 
   1. Analytical flow-frequency: (1) equivalent record length, mean, standard deviation, and skew, or (2) series of peak flows. 
   2. Graphical frequency relationship: at least 8 (preferably 9) flow-frequency coordinates and equivalent record length. Stage-frequency is an option of the hydraulic conditions warrant.
2. Stage-discharge functions consisting of flows and distributions of stages, if frequency function reflects discharge. If frequency function reflects stage, a stage-discharge function is not required.
3. Aggregated stage-damage functions consisting of stages and distributions of damage, which can be manually entered or internally computed. 

If you're using HEC-FDA 2.0 to compute the aggregated stage-damage functions, you will also need:

1. Terrain, for one or both of the following: (1) using HDF results for hydraulics, in which case the terrain should be in HDF format, or (2) using terrain data for ground elevation at structure, in which case the terrain can be imported as a raster data set or HDF. Only one terrain file can be imported.  
2. Hydraulics data set should reflect water surface elevations (not depth) with three data format options: (1) steady or unsteady: 8 subdirectories with raster datasets (2) steady: 1 HDF; or (3) unsteady: 8 HDFs.
3. Discharge-frequency function and stage-discharge function, or stage-frequency function only (same functions mentioned above). 
4. Occupancy types with damage categories, depth-percent damage functions with uncertainty, first floor elevation uncertainty, and either: (1) structure/content/other value uncertainty, or (2) content-to-structure value ratios with uncertainty and other-to-structure value ratios with uncertainty. Content, vehicle, and other configuration is optional. 
5. Structure inventory in the form of a point shapefile with at least a structure ID, structure value, first floor elevation (or ground elevation and foundation height) and occupancy type. Optionally: content value, other value, beginning damage depth, among others. 

Stage-Damage H&H Data

• There are three types of engineering data required for a stage-damage compute: a frequency function, a stage-discharge function if frequency reflects flows, and a hydraulics data set. Double-check that the project conditions are the same across the three items. The computed stage-damage function will not make sense if: (1) with-project conditions are unique from without-project conditions, and (2) with-project data is used along with without-project data for the without-project set of stage damage functions. 
• Ensure that the coordinate reference system is either set to be the same across all geospatial data sets, and/or that the study coordinate reference system is set by selecting the study projection from the study properties editor under the File menu (best practice). The coordinate reference system should match that of the hydraulics modeling.

Optional items include:

1. Index points in the form of a point shapefile, if retrieving graphical stage-frequency from water surface elevations in hydraulics. Index points are not explicitly used for anything else within HEC-FDA, but remain an important concept. 
2. Regulated-unregulated transform function with unregulated flows and distribution of regulated flows.
3. Exterior-interior function with exterior stages and distributions of interior stages. 
4. Levee (top of levee elevation) and optionally system response curve involving stages and distributions of breach probabilities.

Here's what you'll need from engineering

For each alternative-analysis year-impact area combination, you will need from engineering:

• Frequency functions - either (a) or (b) below: 
  1. Analytical flow-frequency: equivalent record length, mean, standard deviation, and skew. 
  2. Graphical frequency relationship: at least 8 (preferably 9) flow-frequency coordinates and equivalent record length. Stage-frequency is an option of the hydraulic conditions warrant.
• Stage-discharge functions consisting of flows and distributions of stages, if frequency function reflects discharge. If frequency function reflects stage, a stage-discharge function is not required. 

The frequency function and stage-discharge function should reflect the same place in the channel, i.e. the same index point. You will also need a data set of hydraulic modeling for each alternative-analysis year combination. The modeling should reflect water surface elevations (not depth) with three data format options: (1) steady or unsteady: 8 subdirectories with raster datasets (2) steady: 1 HDF; or (3) unsteady: 8 HDFs

Create New Study and Compute Workflow

This section walks you through creating a new study and computing all results. This section assumes that you will use HEC-FDA Version 2.0 to compute aggregated stage-damage functions. 

First: Create Study then Import or Specify Study Data

1. Create new study. Set the study properties, including the discount rate, period of analysis, and study projection. 

   1. Be sure to review and update the discounting and price information, highlighted in the image below. 

      

2. Import terrain if using terrain to identify ground elevation at structures or if using hydraulics from HEC-RAS in HDF file.

   1. A name and path to the terrain file are required for import, as in the image below.

      

      Terrain File

      Please note that only 1 terrain file may be imported. Import terrain as a HEC-RAS terrain. A RAS Terrain is a .hdf file paired with one or more .tif files. Select the .hdf file when importing your terrain and ensure the accompanying files are included in the same subdirectory. A terrain file is required if you're relying on hydraulic data in HDFs or if you do not have elevation data in your structure inventory (e.g. only foundation heights but no ground elevations). 

      

3. Import impact area set.

   1. A name, description, shapefile path, and selection for unique impact area name (a field of the attribute table) are required for import.

      

      Impact Area Set File

      Only one set of impact areas may be imported into an HEC-FDA file. This means that all impact areas must be included in one polygon shapefile to be used in a study that contains a field for a unique impact area ID. 

      

4. Import set of eight hydraulic profiles for the without-project condition, and for each with-project condition if the hydraulics are different than the without-project condition. 

   1. For a given hydraulics data set, one HDF is required for steady hydraulics modeling, eight HDFs are required for unsteady hydraulics modeling. Gridded water surface elevation data is accommodated, see Hydraulics for more information. Specify a name, description, source file (or folder for unsteady), and be sure to identify either the correct annual exceedance probabilities or correct return intervals.

      

5. Specify frequency relationships. Frequency relationships should be entered for each project condition-analysis year-impact area combination. 

   1. The frequency relationships may be one of the three below. Please see EM 1110-2-1619, HEC-FDA on Discourse, or speak with HEC about choosing one of the three. Recall that uncertainty in EAD is most sensitive to uncertainty in flow so we want to include flow in our models if the hydrologic and hydraulic conditions permit. 

      1. Analytical flow-frequency function. Select Analytical. Provide the mean, standard deviation, skew, and equivalent record length. See the top image below. 
      2. Graphical flow-frequency function. Select Graphical. Select Flow. Provide at least eight coordinates of exceedance probability and flow, and an equivalent record length. See the bottom image below. 
      3. Graphical stage-frequency function. Select Graphical. Select Stage. Provide at least eight coordinates of exceedance probability and stage, and an equivalent record length.  See the bottom image below. 

      Analytical frequency function 

      

      Graphical Frequency Function

      Right-click on Compute Confidence Limits to view the .025 and .975 confidence limits. 

      

6. Optionally specify regulated-unregulated transform flow relationships. 

   1. Specify with a series of coordinates of unregulated flow and distribution of regulated flow.

      

      
      

7. If using discharge-frequency, specify a stage-discharge relationship.

   1. You'll need to specify a stage-discharge function to accompany each flow-frequency function. Specify with a series of coordinates of flow and distribution of stage. 

      

8. Optionally specify interior-exterior relationships.
9. Optionally specify levees with a top of levee elevation minimally.

   1. Ideally, select user-defined and enter a system response curve in stages and failure probabilities. 

      

10. Import occupancy types.

    1. The recommended workflow is to import occupancy types using the same flat-file format as that which was used for HEC-FDA Version 1.4.3. See Appendix D of the Version 1.4.1 User's Manual for more information. Optionally, occupancy types may be entered manually. The occupancy types editor is the most complicated editor. See the page on the HEC-FDA User Interface for more information. 

       

11. Import structure inventories. 

    1. A structure inventory is imported using a point shapefile, where the attribute table must have the following attributes: unique ID, dollar-denominated structure value, occupancy type, and either both foundation height and ground elevation or just the first floor elevation. Identify whether first floor elevation or foundation height will be used, and if foundation height, identify whether the ground elevations will come from the structure inventory or a terrain file. Select optional attributes and identify what occupancy type names in the structure inventory correspond to which occupancy types in the study database. 

       Select Attributes

       

       Identify Occupancy Types

       

Duplicates Not Needed

1. If a given study data item is the same for multiple project conditions, then that study data item need not be duplicated. For example, assume that you have a flow-frequency function for the existing condition of a given impact area, but the flow-frequency function is also representative of the hydrologic conditions of the future-without project condition, and all with-project conditions. In that case, create one frequency function, and select the same frequency function for each of the Scenarios. 
2. Except for terrain and the set of impact areas, many items can be created for a given study data element. For example, multiple structure inventories can be imported. 

Second: Compute Aggregated Stage-Damage Functions

The following items must be selected for configuration of an aggregated stage-damage compute: 

1. Discharge-frequency function and discharge-stage function or just a stage-frequency function 
2. Hydraulic data set
3. Structure inventory 
4. Occupancy types 

Hit Compute. An aggregated stage-damage function is computed for each impact area, damage category, asset category combination. 

Third: Specify and Compute Scenarios

Specify a scenario for each project condition-analysis year combination. The following must be selected for each impact area for a given scenario:

1. Discharge-frequency function
2. Stage-discharge function 
3. Stage-frequency function if not able to use discharge-frequency function and stage-discharge function 
4. Stage-damage functions, one for each damage category - asset category combination 

The following may optionally be selected for any impact area for a given scenario:

1. Regulated-unregulated flow transform function
2. Interior-exterior stage transform function 
3. Levee elevation, system response curve optionally 
4. Additional thresholds 

Hit Preview Compute to view a deterministic estimate of EAD. After completing the configuration of the scenario for each impact area, hit save and close, right click on the scenario, and hit compute. When the compute is complete, a message will be displayed prompting on whether to display results. 

Fourth: Specify Alternatives and an Alternative Comparison Report

1. Specify Alternatives. An alternative should represent a given project condition and should include one scenario for each analysis year. Right click on each alternative to view results. 
   1. 
2. Specify the Alternative Comparison Report by identifying the without-project condition alternative and each with-project condition alternative for comparison. Right click on the alternative comparison report to view results.
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Helpful Hints About Study Data

Tips and Tricks

• Keep track of the units of measurement. Units of measurement will not be tracked nor handled within HEC-FDA Version 2.0. For example, if terrain elevation is measured in meters but the first floor elevation is measured in feet, HEC-FDA will not know about the discrepancy - this will have to be handled outside of HEC-FDA. 
• Generally, there are five distributional assumptions available for input relationships and uncertainty parameters: Normal, Log Normal, triangular, uniform, and deterministic (no uncertainty). These distributions are specified in their usual way. 

Related Topics

Review the HEC-FDA Quick Start Guides Create New Study from Scratch page for instructional videos for creating a new study from scratch.