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HEC-RAS is a computer program that models the hydraulics of water flow through natural rivers and other channels. The program is one-dimensional, meaning that there is no direct modeling of the hydraulic effect of cross section shape changes, bends, and other two- and three-dimensional aspects of flow. The program was developed by the US Department of Defense, Army Corps of Engineers in order to manage the rivers, harbors, and other public works under their jurisdiction; it has found wide acceptance by many others since its public release in 1995.

3D view

The Hydrologic Engineering Center[1] (HEC) in Davis, California developed the River Analysis System (RAS) to aid hydraulic engineers in channel flow analysis and floodplain determination. It includes numerous data entry capabilities, hydraulic analysis components, data storage and management capabilities, and graphing and reporting capabilities.

How it works[edit]

The basic computational procedure of HEC-RAS for steady flow is based on the solution of the one-dimensional energy equation. Energy losses are evaluated by friction and contraction / expansion. The momentum equation may be used in situations where the water surface profile is rapidly varied. These situations include hydraulic jumps, hydraulics of bridges, and evaluating profiles at river confluences.

For unsteady flow, HEC-RAS solves the full, dynamic, 1-D Saint Venant Equation using an implicit, finite difference method. The unsteady flow equation solver was adapted from Dr. Robert L. Barkau’s UNET package.

HEC-RAS is equipped to model a network of channels, a dendritic system or a single river reach. Certain simplifications must be made in order to model some complex flow situations using the HEC-RAS one-dimensional approach. It is capable of modeling subcritical, supercritical, and mixed flow regime flow along with the effects of bridges, culverts, weirs, and structures.


HEC-RAS is a computer program for modeling water flowing through systems of open channels and computing water surface profiles. HEC-RAS finds particular commercial application in floodplain management and flood insurance studies to evaluate floodway encroachments. Some of the additional uses are: bridge and culvert design and analysis, levee studies, and channel modification studies. It can be used for dam breach analysis, though other modeling methods are presently more widely accepted for this purpose.


HEC-RAS has merits, notably its support by the US Army Corps of Engineers, the future enhancements in progress, and its acceptance by many government agencies and private firms. It is in the public domain and peer-reviewed, and available to download free of charge from HEC's web site. Various private companies are registered as official "vendors" and offer consulting support and add on software. Some also distribute the software in countries that are not permitted to access US Army web sites. However, the direct download from HEC includes extensive documentation, and scientists and engineers versed in hydraulic analysis should have little difficulty utilizing the software.


Users may find numerical instability problems during unsteady analyses, especially in steep and/or highly dynamic rivers and streams. It is often possible to use HEC-RAS to overcome instability issues on river problems. HEC-RAS is a 1-dimensional hydrodynamic model and will therefore not work well in environments that require multi-dimensional modeling. However, there are built-in features that can be used to approximate multi-dimensional hydraulics.

HEC-RAS programs[edit]


Aquaterra is a professional software for canals and river engineering works design. Seamless integration in CAD environment makes it very easy to learn and use. Engineers use Aquaterra to create detailed designs as well as for conceptual studies and designs. HEC-RAS interface is intended for communication between CAD environment and HEC-RAS. This module prepares the HEC-RAS geometric input file based on cross sections, banks and Manning coefficient data and transfers the resulting water levels back to Aquaterra.


HEC-RAS can also be used in the GIS program ArcView (With 3-D analyst and Spatial Analyst extensions). ArcView can read-in AutoCAD drawings for backgrounds and can create a Digital Terrain Model (DTM). In a similar way to river CAD, Geo-RAS can be used to create cross sections and other geometric data for use in HEC-RAS and can be used to export water surface data from HEC-RAS back into ArcView to create flood maps with depths and extents of flooding.


HEC-RAS has a dll library that allows you to create an application for use without a user interface. This dll proved to be useful for advanced analysis such as Monte Carlo uncertainty. The freeware application ARAS[2] takes advantage of such capability, and allows to automate several tasks like running several plans of updating roughness. "RAS" : River Analysis System


HEC-RAS can be used along with AutoCAD. A digital terrain model (DTM) can be constructed in AutoCAD and sections can be cut from the DTM and imported into HEC-RAS.

WMS (Watershed Modeling System)[edit]

WMS (Watershed Modeling System) provides pre and post-processing tools for use with HEC-RAS. The development of WMS was funded primarily by The United States Army Corps of Engineers. Commercial licenses to WMS are available from the developer, Aquaveo LLC.[3] Features include:

  • Use feature objects (centerline, cross section lines) and a TIN to develop the geometry of a HEC-RAS model.
  • Edit, merge, and create cross sections in a database for use with HEC-RAS and other hydraulic models.
  • Delineate flood plains from water surface elevation data. Water surface elevations can be computed by HEC-RAS, defined interactively, or imported from a file.
  • Link multiple simulations of HEC-1 to HEC-RAS to determine the uncertainty in modeling parameters on a delineated flood plain. Curve Number and Precipitation can be stochastically varied among HEC-1 parameters and Manning's n value for HEC-RAS.


  • HEC-Archives by Dodson & Associates, Inc.[4]

(needed: other vendors' products)

See also[edit]


  1. ^ HEC.usace.army.mil
  2. ^ Hometss.com
  3. ^ Aquaveo.com
  4. ^ a Dodson-hydro.com, free download site for archived versions of HEC-RAS and HEC-2]

External links[edit]

Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/HEC-RAS — Please support Wikipedia.
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51 news items

Mon, 09 Nov 2015 02:48:06 -0800

HEC-RAS® è il sistema d'analisi dei fiumi dell'Hydrologic Center (HEC), del Corpo degli Ingegneri dell'Esercito degli Stati Uniti d'America. HEC-RAS® analizza le reti di canali naturali ed artificiali, calcolando i profili del pelo libero basandosi su ...

Vicksburg District, US Army Corps of Engineers (press release)

Vicksburg District, US Army Corps of Engineers (press release)
Thu, 20 Aug 2015 05:22:30 -0700

Since the agreement was signed, HEC SME's have taught classes in hydrologic modeling with HEC-HMS, hydraulic modeling with HEC-RAS, and application of GIS data and tools for hydrologic and hydraulic modeling. Upcoming classes will focus on more ...

Vicksburg District, US Army Corps of Engineers (press release)

Vicksburg District, US Army Corps of Engineers (press release)
Tue, 09 Jun 2015 18:41:15 -0700

In May 2015, RID hosted two members of the CEIWR-HEC-RAS (Hydrologic Engineering Center's River Analysis Systems software) team, Cameron Ackerman and Stanford Gibson, and representatives from the Pacific Ocean Division (POD) John Emmerson ...

Ten Links

Ten Links
Mon, 28 Sep 2015 12:30:00 -0700

Aquaflood 2016 enables multiple data exchange possibilities between CAD and MIKE FLOOD, or CAD and DHI/HEC-RAS platforms. It also supports various Autodesk and BricsCAD platforms, so users can experience many benefits thanks to the wide range ...
Pittsburgh Post-Gazette
Thu, 12 Mar 2015 20:56:15 -0700

The study, called an HEC-RAS study, takes its name from the California-based Hydrologic Engineering Center, or HEC, which developed the river analysis system, or RAS. It provides computer models of flowing water under a variety of conditions.


Wed, 15 Apr 2015 09:08:27 -0700

The model was calibrated using water level and canal discharge data from the field, with HEC-RAS developed as the main predictive modeling tool for general hydraulic impacts because it is widely used in the industry and can be applied to a variety of ...

Emergency Management

Emergency Management
Tue, 07 Apr 2015 08:07:37 -0700

NOAA's Experimental Storm Surge Simulator shows a street-level view of where water could rise in a storm surge. Erin Moody, The Island Packet | April 7, 2015. Example of the experimental Potential Storm Surge Inundation Map. This is a static example of ...


Wed, 11 Mar 2015 07:25:58 -0700

Without a clearly defined process, Black & Veatch prepared a hydraulic model of the Occoquan River using the unsteady module within the U.S. Army Corps of Engineers' river hydraulic model, HEC-RAS, to evaluate the inundation downstream during various ...

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