HEC-RASLAB #1Page 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

PRJMain 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)

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.

  1. 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)

  1. Begin building model.

Start Geometric Data


Select Edit, Geometric Data

  1. 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

4. continued

Enter River Name (TREEO) and Reach Name (MAIN)

  1. 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

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

07

306 THIS IS A TRIANGULAR

504CHANNEL,10:1 SIDE SLOPE

706

907

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 Manning’s 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


SAVE GEOMETRIC DATA, file name automatically assigned


  1. Start Steady Flow Data

Select Edit, Steady Flow Data

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


SAVE STEADY FLOW DATA, file name automatically assigned

  1. 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

  1. 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

  1. 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

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

  1. Generate Report - File, Generate - Select Filename

SAVE PROJECT, file name assigned in step 1.