An Introduction to Green Cities and Comparing HEC-RAS and EPA SWMM: A Quick Guide from Clear Creek Solutions

Welcome back to Clear Creek Solutions’ Hydrology Education Series! In this article, we’ll break down the key differences between two powerful software tools widely used in water resource engineering: HEC-RAS (often referred to as HEC-R) and EPA SWMM. We’ll give you a quick overview of what each tool does, how to access them, and when to use each based on your project needs.

We also have a full playlist of EPA SWMM tutorials on our YouTube channel, so feel free to explore those for more in-depth guidance.

Overview of EPA SWMM and HEC-RAS

EPA SWMM (Storm Water Management Model)

EPA SWMM is designed for planning, analysis, and design of stormwater runoff, sewer systems, and drainage networks. It includes tools for:

• Basic hydrologic modeling

• Hydraulic system design

• Pollutant load estimation

• Running simulations with design storms

• Modeling low-impact development (LID) and green infrastructure features

HEC-RAS (Hydrologic Engineering Center’s River Analysis System)

HEC-RAS is primarily used for river and channel modeling, and excels at:

• 1D and 2D flow simulations

• Water surface profile calculations

• Sediment transport

• Water quality analysis in open channels

• Long-term trend analysis of river systems

Software Access

Both software packages are free to download:

• EPA SWMM can be downloaded from the EPA's website, which also includes a user manual and installation instructions.

• HEC-RAS is available from the U.S. Army Corps of Engineers' website, along with version details and support documents.

Interface and Modeling Capabilities

• EPA SWMM features a layout-based interface where you build your hydraulic network by connecting elements like junctions, storage units, outfalls, and rain gauges. It’s excellent for system design, inflow/infiltration analysis, and evaluating stormwater control strategies.

• HEC-RAS includes the RAS Mapper, offering basic GIS capabilities and detailed visualization of river cross-sections and flow paths. It is better suited for natural channels and floodplain analysis.

Similarities

Both tools share some common features:

• Support for hydraulic modeling

• Ability to perform water quality analysis

• Graphing tools for profile views and flow data analysis

Key Differences

FeatureEPA SWMMHEC-RASIntended UseSewer and drainage system designRiver/channel analysisHydraulic ModelingYesLimited (mainly water surface profiles)Channel Sediment TransportNoYesLID and Green InfrastructureYesNoGIS IntegrationBasic (through RAS Mapper)LimitedFacility Design CapabilitiesYesNo

When to Use Each

Use EPA SWMM if you need to:

• Design and size stormwater or sewer systems

• Conduct flood control studies

• Evaluate LID and green infrastructure impacts

Use HEC-RAS if your focus is to:

• Model water surface profiles

• Simulate 1D or 2D flow in open channels

• Perform sediment transport or river water quality analysis

Hands-On Overview

Inside the software:

• EPA SWMM allows you to build and analyze systems with interactive elements like storage units, rain gauges, and junctions.

• HEC-RAS lets you define river geometry, import cross-section data, and simulate detailed profiles and flow networks.

Final Thoughts

Both HEC-RAS and EPA SWMM are incredibly useful, but each excels in its own domain. Whether you're planning urban drainage or simulating river dynamics, understanding their strengths will help you choose the right tool for your project.

For more guides, walkthroughs, and tips, check out our tutorials on YouTube or leave a comment if you have questions—we're happy to help!

Thanks for reading, and we’ll see you in the next tutorial!+-