1. HEC-RAS Version 3.1 Overview
Presented by:

2. HEC-RAS US Army Corps of Engineers’ Hydraulic Engineering Center
River Analysis System
Version 2.0 (Windows 3.1 or later) - April 1997
Version 2.1 (Windows 95/98 or NT(4.0)) - October 1997
Version 2.2 (Windows 95/98 or NT(4.0)) - September 1998
Version 3.0 (Windows 95/98 or NT(4.0))
Version 3.1 (Windows 95 or higher) January 2003

3. NRCS is adopting the Corps of Engineer's HEC-RAS (River Analysis System) for computation of water surface profiles. Use of the NRCS program WSP2 is being phased out as NRCS engineers become trained and experienced with HEC-RAS.

4. National Bulletin No. 210-01 September 30, 2000
NRCS will no longer support our WSP2.
Announce adoption of Hydrology Engineering Center-River Analysis (HEC-RAS).
HEC-RAS Leadership - National Water and Climate Center and NRCS HEC-RAS Team

5. HEC-RAS Team

6. HEC-RAS is software that allows the user to perform one dimensional steady and unsteady flow river hydraulics calculations go to:

7. Hydraulic Information - It’s Important
Water surface profiles
Hydraulic Parameters

8. Hydraulic Parameters
Velocity
Depth
Shear
Width
Area
etc

9. Hydraulic Computer Models: Why do we care?
Direct Measurements: hard, expensive, dangerous
Analytical: predictive

10. Hydraulic Models Steady Flow WSPRO (FHA) WSP2
HEC-2 (last one out in 1991)
HEC-RAS (released 1995)
Unsteady Flow
UNET
DAMBREAK
HEC-RAS
FHA
SCS
COE
last version of HEC2 was 1991, still has bugs, esp. at transition at bridge, may jump to pressure with HECRAS
FEMA - interested in consistency, not hydraulic theory
New studies or restudy, use HECRAS
Small modification, use HEC2 (which version-esp. if less than 1 ft impt)
If can’t find, try to match old profile with HECRAS and go from there

11. Comparison of HEC-2 and HECRAS
Improved conveyance calculations.
Mixed flow - supercritical, subcritical
Bridge hydraulics - more options
Culvert hydraulics - more options
Junctions - both energy and momentum
Others - interpolation, unsteady flow, more section definition, etc
HEC2 calculated between points - can get different values depending upon the number of points in a section
HECRAS calculates it at n break points

12. Comparison of WSP2 and HEC-RAS
DOS command line - batch jobs
One dimensional steady flow
Subcritical and critical flows
No graphics
Windows graphical interface for Win3.1, Win95/98, and WinNT
One dimensional steady flow
floodway encroachments
unsteady flow
sediment transport
Subcritical, critical, mixed and supercritical flows
Graphical display of all geometric data and output including 3D views

13. Comparison of WSP2 and HEC-RAS
Uses friction slope from upstream x-section only (i.e. upstream x-section represents entire reach).
Uses average of friction slope from upstream and downstream x-sections.

14. HEC-RAS Hydraulic Analysis Components Graphical User Interface
Data Input
Output

15. Hydraulic Capabilities
Steady flow water surface profiles - single reach, dendritic, mixed flow regime.
Unsteady flow simulation- full network of open channels, adapted from UNET
Sediment transport/Movable boundary- long term trends of scour and deposition (not ready, only bridge scour)

16. Data Input Flows Geometry Manning’s n Calibration Data Cross Section
Spacing
Structures
Manning’s n
Calibration Data
Cross section at where geometry changes, can interpolate but straight
spacing - steeper slopes require closer spacing (streams at 50’, larger rivers at 1000ft, Miss at a mile. Min spacing of 1’, otherwise may drop all friction loss

17. Flow Data

18. Reach

19. Background Pictures

20. Cross
Section

21. Trouble Shoot Cross Section Data

22. Edit/Review roughness for reach

23. Bridge Input

24. Output
Graphical
Tabular
Profile
Section

25. Tabular
Data Output

26. Profile Plots

27. Rating Curve

28. 3-D Plots

29. Flow Distribution
Use Caution
It's still a 1-D model

30. Channel
Modification

31. Other Applications and Capabilities
Bridge Scour
Culverts
Drop Structures
Hydraulic Jumps
Split Flow
Lateral Weirs
In Channel Weirs
Gated Spillways and Weirs
Vertical Variation in Roughness
GIS import and export features (HEC-GeoRAS 3.1 with ArcView)

32. How do you get HEC-RAS?
The HEC-RAS software and manual are available for free download from HEC at the following internet address:
Also available through NRCS CCE and NWCC web site.

33. HEC-RAS - Documentation
User’s Manual: provides an introduction and overview of the modeling system, installation instructions, how to get started, a simple example, detailed descriptions of each of the major modeling components, and how to view graphical and tabular output
Hydraulic Reference Manual: describes the theory and data requirements for hydraulic calculations
Applications Guide: contains a series of examples that demonstrate various aspects of HEC-RAS.

34. Hardware & Software Requirements for HEC-RAS
IBM compatible machine with 486 or higher
10 MB free space on hard drive (20 recommended)
16 MB of RAM for Windows95/98 and 24 MB for Windows NT (32 or more is recommended)
Mouse
Windows95/98 or Windows NT (4.0 or higher)
Color VGA or better video display

35. Limitations
Flow is constant with respect to time (unsteady is optional)
Flow is gradually varied with distance
Dominant flows in x direction (1-D)
Channel slopes less than 1:10H
These are limitations of 1-D energy eqns
Unsteady addition
estuaries or bays have side momentum
Junctions are 2-D, don’t have a section at a junction

36. Where do you go for help? On line help HEC-RAS documentation
HEC-RAS Support Team from NRCS (

37. The HEC-RAS software is an engineering tool.
Not a replacement for sound engineering.
The HECRAS software is an engineering tool. Input and output should be examined carefully.
Computational software is NOT a replacement for sound engineering and application of engineering judgment.

38. Agenda Tuesday: Hydraulics Review, Basic I/O, Bridges
Wednesday: Culverts, Tributaries, weir and drop structures
Thursday: Other features, Channel Modification, Unsteady Flow

39. The End