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

Criterion	Explanation
General Description	Hydrologic Engineering Center's River Analysis System (HEC-RAS) is a modeling platform that allows the user to perform one-dimensional steady flow, one and two-dimensional unsteady flow calculations, sediment transport/mobile bed computations, and water temperature/water quality modeling. The model is designed to perform one and two-dimensional hydraulic calculations for a full network of natural and constructed channels.
Model Domain	The model domain is flexible, specified by user.
Developer	US Army Corps of Engineers (USACE)
Hardware computing requirements	Processer 3.4 Ghz or higher for 1D model. 2D model: processors of > 3.2- 3.4 Ghz. >32 Gb RAM. 24-inch (or larger) dual monitors. Windows 7, 8, 8.1 and 10 64-bit only.
Code language	Visual Basic
Original application	Modeling of hydrodynamics in river systems
Public/proprietary and cost	The model is available for the public to download
Physically or empirically based	Physically based
Mathematical methods used	One- and two-dimensional unsteady flow simulation, steady transport/movable boundary computations, water quality analysis Steady flow simulation: solution of the one-dimensional energy equation Unsteady flow simulation: hydraulic calculations for steady flow were incorporated into the unsteady flow module Sediment transport/ movable boundary computations: 1D sediment transport from scour and deposition
Input data requirements	Geometry data, boundary flow/stage data, water quality data, meteorological data
Outputs	Flow, stage, velocity, water quality variables
Pre-processing and post-processing tools	New RAS mapper pre-processor tools allow users to extract 1D rivers, cross sections, storage areas and 2D model elements. RAS mapper is a post-processor generates inundation depth and floodplain boundary datasets, using geometry and computed water surface profiles.
Representation of uncertainty	None specified.
Prevalence	Widely applied in different river systems, potentially hundreds of applications worldwide
Ease of use for public entities	Needs knowledge and experience in hydraulic and water quality modeling. Model parameterization and calibration are needed for new applications.
Ease of obtaining information and availability of technical support	The HEC-RAS website provides technical support to HEC-RAS users. The website provides resources for users to download software, learn how to use the model, resolve problems, report bugs, and suggest improvements to products and service. No phone or email technical support is available to non-USACE customers.
Source code availability	The HEC generally discourages the distribution of source code. The center will provide source code if requested, for importing to different computers or for modifying. Source code under development will not be distributed.
Status of model development	Version 5.0.5 is latest version and is now available. This version supersedes all previous versions.
Challenges in integration	Provides inputs and outputs in ascii and binary format, which can be processed in DSS format, and can be easily integrated with other models.

References

US Army Corps of Engineers (USACE) Hydrologic Engineering Center (HEC). 2016. HEC-RAS River Analysis System. User's Manual. Version 5.0, February 2016. CPD-68.

US Army Corps of Engineers (USACE) Hydrologic Engineering Center (HEC). 2018. Hec-RAS River Analysis System. Supplemental User's Manual. CPD-68d.

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