Hydrologic and Hydraulic Uncertainties

Workshop Overview

The goal of this workshop is to familiarize students with using HEC-FDA Version 2, including navigating the user interface for importing hydrologic data and for defining exceedance-probability and stage-discharge functions, and their associated uncertainties.

• Steps already completed for the students include:
  • Creating the study
  • Importing the terrain and impact area set.
• Students will complete the following steps in this workshop:
  • Import the hydraulic data
  • Enter the exceedance probability functions
  • Enter the stage-discharge functions with uncertainty

Introduction

The hydrologic and hydraulic data you're working with are from a section of the White River in Muncie, Indiana. The example data set draws on an example data set used in HEC-RAS Training. The 0.02 annual chance exceedance (50-year) floodplain is illustrated in the image below. 

Instructions

Task 1 – Open Study for Workshop 2

1. Open the HEC-FDA Version 2 software. 
2. From the File menu, click Open. The Open Study dialog opens as a tab.
3. Click the ellipse button in the Study Path box to open the Select File browser window.
4. Navigate to the Workshop 2 starting project (e.g., C:\Workshops\FDA\Workshops\Muncie), select the *.sqlite HEC-FDA file and click Open.
5. From the Open Study tab, click OK.

Task 2 – Import Hydraulic Data

Considerations

Hydraulic modeling is used in HEC-FDA to identify the water surface elevation at each structure for, ideally, at least 8 unique events. This information is used in calculating the stage-damage functions for each structure. The structure-level stage-damage functions (aka consequence functions) are then aggregated to stages at the index point, which are defined by the combination of the input summary relationships. The hydraulics data can also be used to develop graphical stage-exceedance probability functions. Hydraulic engineers will use HEC-RAS or other hydraulic modeling software to develop the spatial data sets like the ones used in this workshop.

Steps

1. From the Study Tree under Hydraulics right-click on the appropriate spatial data sets type, and click Import Hydraulics. The Import Hydraulics dialog opens as a tab.
   

   Test Your Knowledge - Question 1

   Which import option should be selected to import the hydraulic data?

   1. Unsteady HDF
   2. Steady HDF
   3. Gridded Data

   

   Review the Example Study Data to determine the correct spatial data set type for the Muncie, Indiana Hydraulic study data.

    

2. From the importer enter a name for the hydraulics profile (e.g., Existing Conditions) and enter a description for the profile.
3. From the Source File box select the ellipse button to open the Select File browser window.
4. Navigate and select the folder containing the existing conditions hydraulic data (e.g., C:\Workshops\FDA\MuncieData\Hydraulics\Muncie_Existing_Conditions), and click Select Folder.

5. The importer tab updates with a table displaying the name of the profiles, the annual exceedance probability and the return interval. The Annual Exceedance Probability will need to be corrected. Manually enter the appropriate AEP value for each profile name based on Table 1.

   Table 1
   Name	Annual Exceedance Probability	Return Interval (Return Period)
   20%ACE	0.2	Updates based on the entered AEP using the equation (1/AEP)
   10%ACE	0.1
   5%ACE	0.05
   50%ACE	0.5
   2%ACE	0.02
   1%ACE	0.01
   0.5%ACE	0.005
   0.2%ACE	0.002

   

   Copy and paste is not an option in the import table. Select each cell to type in the appropriate return interval.

6. Note that the Return Interval column updates based on the AEP. Check that the AEP and return interval values are correct and click Save. The hydraulic data is added to the Study Tree.
7. Click Close to close the Import Hydraulics tab.

Task 3 – Enter the Flow-Frequency Function

Steps

1. From the Study Tree, right-click on Frequency Functions and select Create New Frequency Function. The Create Frequency Function opens as a tab.
2. Enter a name for the function in the Name box (e.g., Flow-Frequency LPIII), and enter a description for the frequency function (e.g., Flow-Frequency LPIII distribution for a period of record (Record Length) of 48 years).

3. Select Analytical and enter the LP3 Parameters listed below. 

   Mean	Standard Deviation	Skew	Record Length
   3.707	0.24	-0.475	(see Test Your Knowledge - Question 2)

   Test Your Knowledge - Question 2

   What is the correct Record Length (period of record) value for the flow-frequency LPIII distribution?

   

   Review the Example Study Data for Version 2 to determine the correct Record Length for the Flow Frequency Function.

4. Enter the correct period of record in the Record Length box.
5. Click Save. The flow-frequency function is added to the Study Tree.
6. Click Close to close the Create Frequency Function tab.

Task 4 – Enter the Without-project Condition Stage-Discharge Function

Steps

1. From the Study Tree, right-click on Stage-Discharge Functions and select Create New Stage-Discharge Relationship. The Create New Stage-Discharge Relationship opens as a tab.

2. Enter a name for the relationship in the Name box (e.g., Existing Condition Relationship, Rating Curve Without Project, etc.), and enter a description for the relationship (e.g., This stage-discharge function represents the relationship between stage and discharge for the without-project condition.).

   Test Your Knowledge - Question 3

   What is the correct Distribution Type for the without-project stage-discharge relationship?

   

   Review the Example Study Data for Version 2 to determine the correct without-project condition stage-discharge function.

3. Select Triangular from the Distribution Type dropdown box.
4. Use the information in Table 3 to create the new stage-discharge relationships for the without-project condition. 
   Table 3

   {"name":"MuncieData.xlsx","sheet":"ExistingConditions_Bank943","page":"Example Study Data","type":"xlsx","pageID":"152636670","space":"FDAUM"}

   Loading

5. Click Save.

Test Your Knowledge - Question 5

In the Study Tree, right-click on the frequency function you just created and select edit. Hit the pop-out icon to the left of the close file icon at the top of the tab. Click inside the plot to get the tooltip (yellow callout box) to inspect the plot a little closer (you can also use the mouse scroll wheel to zoom in or out). Use the plot of the flow-frequency function and the table for the rating curve to identify the most likely stage that has an approximate 0.4% chance of being exceeded. 

Review the Flood Risk Assessment and HEC-FDA for an example of how to work through this problem (specifically the Getting to Damage-Frequency section).

Conclusion

Download the solution project below to compare to your project:

• Muncie_WS2.7z
• Muncie_WS2.zip

Review the best answers to test your FDA knowledge questions and compare with yours to see how you did!

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Best Answers to Test Your FDA Knowledge Questions

Related Topics

• Page:
  Analytical Frequency Function (HEC-FDA User Manual)
• Page:
  Continuous Distributions (HEC-FDA Technical Reference)
• Page:
  Flood Risk Assessment and HEC-FDA (HEC-FDA User Manual)
• Page:
  Frequency Functions (HEC-FDA User Manual)
• Page:
  Getting Help and Additional Resources (HEC-FDA User Manual)
• Page:
  Glossary (HEC-FDA User Manual)
• Page:
  Graphical Frequency Function (HEC-FDA User Manual)
• Page:
  Hydraulics (HEC-FDA User Manual)
• Page:
  Known Issues (HEC-FDA User Manual)
• Page:
  Projection of Geospatial Data Sets (HEC-FDA User Manual)
• Page:
  Recommended GIS Skills (HEC-FDA User Manual)
• Page:
  Study Dimensions and Compute Configuration and Results (HEC-FDA User Manual)
• Page:
  Version 2.0 Certification Report (HEC-FDA User Manual)
• Page:
  Version 2.1 Certification Report (HEC-FDA User Manual)