HEC-RAS LAB #1 Page 1 of 10
TRIANGULAR OPEN CHANNEL
Project File: LAB_1.PRJ
HEC-RAS input files for example problem with single triangular open channel.
Input data for open channel, copy cross sections, and interpolate cross sections..
Generate program files, perform analysis and review output. Discussion of output
formats available from HEC-RAS (e.g., charts, tables, figures).
Problem Statement: One river reach (River TREEO, Reach Main) discharges
into a downstream basin outlet. The peak discharge has been calculated at 50 cfs,
using other methodology for input into HEC-RAS. The reach is 800 feet long.
To Do: Prepare a backwater profile analysis along the creek.
NOTE:
Projects consist of multiple files with multiple file extensions.
Extension: File Description
PRJ Main Project File
G** Geometry File
F** Steady Flow File
P** Plan File
R** Run File (contains results)
O** Output File (used to create graphs and tables)
HEC-RAS LAB #1 Page 2 of 10
TRIANGULAR OPEN CHANNEL
Lab #1 Steps to Develop the HEC-RAS Model:
1. Open HEC-RAS
Go to Windows Start, Programs, HEC, and click on the HEC-RAS icon.
2. Enter Project Information
Select File, New Project
Create Directory: Problems (enter)
Enter Short Project ID and Project Filename (extension is added automatically)
Short Project ID: RAS LAB 1
Project Filename: RASLAB1 (extension is added automatically)
Add Project Description: RAS LAB # 1 (optional information)
HEC-RAS LAB #1 Page 3 of 10
TRIANGULAR OPEN CHANNEL
3. Begin building model.
Start Geometric Data
Select Edit, Geometric Data
Reaches
Cross Sections
4. Add Reaches and Cross Sections
Draw Reach by Selecting the Reach Button (Click Once)
Move over screen to draw reach
Define Reach proceeding from upstream to downstream
With cursor in draw screen, click mouse button once to start
Move cursor, click mouse button once to add point, change direction
At downsteam point, doubleclick mouse button to end
HEC-RAS LAB #1 Page 4 of 10
TRIANGULAR OPEN CHANNEL
4. continued
Enter River Name (TREEO) and Reach Name (MAIN)
5. Add Cross Sections to Reach
Select Cross Section Button (click once)
Select Options, Add a new Cross Section
Enter Station Location (1.0)and Cross Section Description (optional)
Station must be numerical value and are defined as follows:
lower station downstream, higher stations upstream
HEC-RAS LAB #1 Page 5 of 10
TRIANGULAR OPEN CHANNEL
Cross Section Data
Cross Sections typically enter left to right looking downstream
Cross Section Stationing in left column
Elevation Data in right column
Triangular Channel
Station Elevation
0 7
30 6 THIS IS A TRIANGULAR
50 4 CHANNEL,10:1 SIDE SLOPE
70 6
90 7
Enter downstream reach lengths for main channel and overbanks
No downstream reach lengths for most downstream section
Furthest downstream section defined by boundary conditions
Add Mannings n value for main channel and overbanks
.04 .035 .04
Outer Banks are outside Main Channel.
Must correspond to a cross section station.
Left Main Channel Bank at 30 Right Main Channel Bank at 70
Repeat for additional Cross Sections
Use Add, Copy, Interpolate
Copy - Define New Cross Section Name: 9.0
Adjust Elevation: +4 feet (1/2 percent slope)
Revise Downstream Reach Lengths: 800 feet
Exit Cross Section Data Editor
Interpolate - On main geometry screen
Tools, XS Interpolation, Within a Reach
Maximum distance: 100 feet
Interpolate XSs, Close
Interpolated Cross Sections have * by station name
Interpolated Cross Sections can be made permanent by
editing the name in the cross section editor and
removing the asterisk
HEC-RAS LAB #1 Page 6 of 10
TRIANGULAR OPEN CHANNEL
SAVE GEOMETRIC DATA, file name automatically assigned
6. Start Steady Flow Data
Select Edit, Steady Flow Data
HEC-RAS LAB #1 Page 7 of 10
TRIANGULAR OPEN CHANNEL
Enter the Flow for the River TREEO and Reach Main : 50 cfs
(this is the flow at the upstream cross section of each)
Enter Boundary Conditions
Most Downstream Channel
- use Known Water Surface Elevation
- Critical Depth, determined by size of channel
- Normal Depth defined by channel shape, slope, and flow
- Rating Curve (user defined)
- HEC-RAS will normally set these automatically
Normal Depth,
slope = 0.005
SAVE STEADY FLOW DATA, file name automatically assigned
HEC-RAS LAB #1 Page 8 of 10
TRIANGULAR OPEN CHANNEL
7. Simulate Backwater Analysis
Select Run, Simulate
Select Geometry File: TREEO LAB 1
Select Steady Flow File
Save Steady Flow Analysis File
Description: TREEO LAB 1 Short Form: LAB 1
8. COMPUTE
Options within this segment allow for error checking, precision, etc.
See FINISHED COMPUTATION screen for errors and warnings.
Close Window
EXIT STEADY FLOW ANALYSIS
HEC-RAS LAB #1 Page 9 of 10
TRIANGULAR OPEN CHANNEL
9. View Results
View Graphics
Cross Sections
Profiles
Rating Curves (multiple profiles)
X-Y-Z Perspective (3-D)
View, X-Y-Z Perspective Plot
View, Water Surface Profile
print using File, Print from screen or copy to Windows clipboard
HEC-RAS LAB #1 Page 10 of 10
TRIANGULAR OPEN CHANNEL
View Tables
Cross Sections/Culverts/Bridges
Profile Table
Summary Errors/Warnings
print using File, Print from screen or copy to Windows clipboard
Cross Section 2.0: Water Surface Elevation = 5.94 feet
10. Generate Report - File, Generate - Select Filename
SAVE PROJECT, file name assigned in step 1.
