HEC-RAS Version 3.1 Overview Presented by:

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)) - 2001 Version 3.1 (Windows 95 or higher) January 2003

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.

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

HEC-RAS Team

HEC-RAS is software that allows the user to perform one dimensional steady and unsteady flow river hydraulics calculations go to: www.hec.usace.army.mil

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

Hydraulic Parameters Velocity Depth Shear Width Area etc

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

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

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

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

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.

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

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)

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

Flow Data

Reach

Background Pictures

Cross Section

Trouble Shoot Cross Section Data

Edit/Review roughness for reach

Bridge Input

Output Graphical Tabular Profile Section

Tabular Data Output

Profile Plots

Rating Curve

3-D Plots

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

Channel Modification

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)

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

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.

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

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

Where do you go for help? On line help HEC-RAS documentation HEC-RAS Support Team from NRCS (email: hecrasteam@wcc.nrcs.usda.gov)

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.

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

The End