Getting Started with HEC-RAS: Installation and First Launch

HEC-RAS (Hydrologic Engineering Center - River Analysis System) is the industry-standard software for hydraulic modeling of rivers, streams, and engineered channels. Developed by the U.S. Army Corps of Engineers (USACE), HEC-RAS is free, powerful, and used worldwide for flood studies, dam breach analysis, bridge and culvert design, and floodplain mapping.

This tutorial guides you through downloading, installing, and launching HEC-RAS 6.x for the first time.

What Is HEC-RAS?

HEC-RAS is a comprehensive hydraulic modeling system that computes water surface profiles, velocities, and other hydraulic parameters for natural and constructed channels. Originally focused on one-dimensional (1D) steady flow, modern versions now include 1D/2D unsteady flow, sediment transport, and water quality modeling.

Key Capabilities

HEC-RAS provides the following modeling capabilities:

• Steady Flow Water Surface Profiles: Calculate water surface elevations for gradually varied flow conditions in natural and artificial channels
• Unsteady Flow Simulation: Model flood wave propagation, dam breaks, and time-varying hydraulic conditions
• 2D Flow Modeling: Simulate complex flow patterns in floodplains, wetlands, and coastal areas where 1D assumptions break down
• Sediment Transport: Analyze long-term channel changes due to erosion and deposition
• Water Quality Analysis: Model temperature, dissolved oxygen, and other constituents
• Bridge and Culvert Hydraulics: Compute headwater elevations and flow distributions through structures

When to Use HEC-RAS

HEC-RAS is the appropriate tool for many hydraulic engineering applications:

Steady vs. Unsteady Flow

Understanding the difference between steady and unsteady flow analysis is fundamental:

Steady Flow assumes discharge is constant over time at each location. Use this for:

• Design flood analysis (e.g., 100-year flood)
• FEMA flood insurance studies
• Normal operating conditions
• Simple backwater calculations

Unsteady Flow simulates how discharge and water surface change over time. Use this for:

• Dam breach analysis
• Flood routing through systems
• Tidally influenced waterways
• Storage routing in floodplains

System Requirements

Before installing HEC-RAS, verify your computer meets these requirements.

Minimum Requirements

Recommended Specifications

For complex 2D models and large terrain datasets:

Software Dependencies

HEC-RAS 6.x requires:

• 64-bit Windows: 32-bit systems are not supported
• .NET Framework 4.8: Usually pre-installed on Windows 10/11
• Visual C++ Redistributable: Included with installer

Downloading HEC-RAS

HEC-RAS is available free of charge from the official USACE Hydrologic Engineering Center website.

Step 1: Visit the HEC Website

Navigate to the official HEC-RAS download page: https://www.hec.usace.army.mil/software/hec-ras/

Step 2: Review Version Information

1. Check the current stable version (6.x series)
2. Review the release notes for new features and bug fixes
3. Note system requirements and known issues

Step 3: Download the Installer

1. Click on the Downloads section
2. Select the appropriate installer (typically HEC-RAS 6.x Installer)
3. You may need to accept a license agreement
4. The download is approximately 800 MB to 1 GB
5. Save the file to a known location

Step 4: Verify the Download

If checksums are provided:

1. Open PowerShell in the download folder
2. Run: Get-FileHash .\HEC-RAS_6x_Setup.exe -Algorithm SHA256
3. Compare with the published checksum
4. Re-download if values do not match

Installing HEC-RAS

The installation process is straightforward but requires administrator privileges.

Step 1: Run the Installer

1. Locate the downloaded file (e.g., HEC-RAS_6.5_Setup.exe)
2. Right-click and select Run as administrator
3. Click Yes if prompted by User Account Control

Step 2: Accept the License Agreement

1. Read the software license agreement
2. HEC-RAS is public domain software developed by the U.S. Government
3. Click I Agree to accept and continue

Step 3: Choose Installation Location

1. The default path is C:\Program Files\HEC\HEC-RAS\6.x
2. You may change this if needed
3. Ensure adequate disk space (2+ GB)
4. Click Next to continue

Step 4: Select Components

The installer offers these components:

Keep all components selected for the complete installation.

Step 5: Create Shortcuts

Choose whether to create:

• Desktop shortcut: Quick access to launch HEC-RAS
• Start Menu folder: Access from Windows Start menu

Both are recommended for convenience.

Step 6: Complete Installation

1. Review your selections
2. Click Install to begin
3. Wait for installation to complete (5-10 minutes)
4. Click Finish when done

Launching HEC-RAS for the First Time

Starting the Application

Launch HEC-RAS using one of these methods:

1. Desktop Shortcut: Double-click the HEC-RAS icon
2. Start Menu: Navigate to Start > HEC > HEC-RAS 6.x
3. File Association: Double-click any .prj project file

The Main Window

When HEC-RAS opens, you will see the main interface with:

• Title Bar: Displays current project name
• Menu Bar: Access to all commands and editors
• Toolbar: Quick access buttons for common functions
• Project Information: Displays basic project settings
• Status Bar: Shows current status and messages

Primary Interface Components

HEC-RAS organizes functionality into separate editors accessed from the main window:

Initial Configuration

Before creating your first model, configure these settings.

Setting System Units

HEC-RAS supports both US customary and SI (metric) units:

To set system units:

1. Go to Options > Unit System
2. Select US Customary or SI (Metric)
3. Choose this before creating a new project

Display Preferences

Configure display settings through Options > Display Preferences:

• Default map colors: Customize channel, overbank, and structure colors
• Line thicknesses: Adjust for visibility on high-resolution displays
• Font sizes: Scale for your monitor resolution

Default Directories

Set your preferred working directories:

1. Go to Options > Directories
2. Configure default locations for:
   • Projects: Where your HEC-RAS projects will be saved
   • Terrain Data: Location for DTM/DEM files
   • Output: Where results files are written

Understanding HEC-RAS Projects

A HEC-RAS project consists of multiple related files stored in a project folder.

Project File Structure

The ## represents version numbers (01, 02, etc.) allowing multiple versions of each component.

Project Organization

HEC-RAS creates a folder structure for projects:

ProjectName/
  ProjectName.prj          (main project file)
  ProjectName.g01          (geometry version 1)
  ProjectName.f01          (steady flow version 1)
  ProjectName.p01          (plan version 1)
  ProjectName.O01          (output version 1)
  Terrain/                 (terrain data subfolder)
  Maps/                    (map output subfolder)

Exploring Example Projects

HEC-RAS includes example projects to help you learn the software.

Accessing Examples

1. Go to File > Open Project
2. Navigate to the HEC-RAS installation directory
3. Open the Example Projects folder
4. Select a sample project

Available Examples

Explore these examples by opening them, examining the geometry and flow data, running simulations, and viewing results.

Where to Find Help

HEC-RAS provides extensive documentation and support resources.

Built-In Documentation

• Help > HEC-RAS Help: Opens the comprehensive help system
• Help > User’s Manual: Full PDF documentation
• Help > Hydraulic Reference Manual: Technical computation methods
• Help > Applications Guide: Step-by-step examples
• Context-Sensitive Help: Press F1 in any dialog for specific guidance

Official Documentation

Key references from USACE:

Online Resources

• HEC Website: Official downloads, documentation, and updates
• USACE Learning Center: Training courses and webinars
• HEC-RAS Community Forums: User discussions and troubleshooting
• University Courses: Academic training materials and tutorials

Troubleshooting Common Issues

HEC-RAS Will Not Start

Missing DLL errors:

• Reinstall HEC-RAS to restore missing files
• Install Visual C++ Redistributable (included with HEC-RAS installer)
• Check that .NET Framework 4.8 is installed

Permission errors:

• Run as administrator for first launch
• Check write permissions to installation directory
• Avoid installing to protected system folders

Crashes on startup:

• Check graphics driver compatibility
• Disable hardware acceleration temporarily
• Verify 64-bit Windows is installed

Display Issues

Blank or corrupted graphics:

• Update graphics drivers
• Check DirectX installation
• Try software rendering mode

Text or icons too small:

• Adjust Windows display scaling
• Modify HEC-RAS display preferences
• Use a lower resolution monitor setting

RAS Mapper not loading terrain:

• Verify terrain file format is supported (GeoTIFF, ESRI Grid)
• Check file path for special characters
• Ensure adequate graphics memory

Performance Issues

Slow 2D simulations:

• Reduce 2D area computational cell size (larger cells = faster)
• Ensure dedicated GPU is being used
• Increase RAM allocation
• Use SSD storage for terrain data

Slow cross-section plotting:

• Reduce number of displayed profiles
• Close unused output windows
• Update graphics drivers

Next Steps

Now that HEC-RAS is installed and running, you are ready to:

1. Create your first model: Your First HEC-RAS Model - Build a steady flow model
2. Master cross-sections: Cross-Section Geometry - Define channel geometry properly
3. Try 2D modeling: 2D Modeling Basics - Two-dimensional flow analysis

References

1. U.S. Army Corps of Engineers, Hydrologic Engineering Center. (2024). HEC-RAS River Analysis System User’s Manual, Version 6.5. Davis, CA: USACE.

2. U.S. Army Corps of Engineers, Hydrologic Engineering Center. (2024). HEC-RAS River Analysis System Hydraulic Reference Manual, Version 6.5. Davis, CA: USACE.

3. U.S. Army Corps of Engineers, Hydrologic Engineering Center. (2024). HEC-RAS River Analysis System 2D Modeling User’s Manual, Version 6.5. Davis, CA: USACE.

4. Brunner, G.W. (2016). “HEC-RAS River Analysis System: 2D Modeling User’s Manual.” U.S. Army Corps of Engineers, Hydrologic Engineering Center, Davis, CA.

Summary

You have successfully installed HEC-RAS and are ready to begin hydraulic modeling. Key takeaways:

• HEC-RAS is free, powerful software for 1D/2D hydraulic analysis developed by USACE
• Download only from the official HEC website
• Choose your unit system before creating projects
• Start with steady flow analysis to learn the basics
• Explore the example projects to understand HEC-RAS capabilities
• The Hydraulic Reference Manual explains the computational methods

Continue to Your First HEC-RAS Model to start building a steady flow model.