Difference between revisions of "HEC-RAS"

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=Quick summary=
 
=Quick summary=
[[file:casimir_fish.png|thumb|450px|Figure 1: CASiMiR model of river stretch and results for adult barbel.]]
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[[file:casimir_gui.jpg|thumb|250px|Figure 1: HEC-RAS graphical user interface (GUI) (source: https://www.hec.usace.army.mil/software/hec-ras/).]]
[[file:casimir_hydropeaking.png|thumb|450px|Figure 2: Example of an operational mitigation measure: reduced downramping rate.]]
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[[file:hecras_cross_sections.png|thumb|250px|Figure 2: HEC-RAS output: cross sections (source: https://www.hec.usace.army.mil/software/hec-ras/).]]
[[file:casimir_migration.png|thumb|450px|Figure 3: Predicted migration paths based on rheoreactive behaviour of grayling.]]
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[[file:hecras_profiles.png|thumb|250px|Figure 3: HEC-RAS output: river profiles (source: https://www.hec.usace.army.mil/software/hec-ras/).]]
[[file:casimir_interface.png|thumb|450px|Figure 4: view of the CASiMiR interface.]]
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[[file:hecras_rating_curve.png|thumb|250px|Figure 4: HEC-RAS output: rating curve (source: https://www.hec.usace.army.mil/software/hec-ras/).]]
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[[file:hecras_stage.png|thumb|250px|Figure 5: HEC-RAS output: hydrograph and stage(source: https://www.hec.usace.army.mil/software/hec-ras/).]]
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[[file:hecras_mapper.jpg|thumb|250px|Figure 6: HEC-RAS output: inundation mapping (source: https://www.hec.usace.army.mil/software/hec-ras/).]]
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[[file:hecras_output.png|thumb|250px|Figure 7: HEC-RAS output: tabular output (source: https://www.hec.usace.army.mil/software/hec-ras/).]]
  
Developed by: CEIWR-HEC, the Hydrologic Engineering Center an organization of the United States Corps of Engineers (USACE) Institute for Water Resources
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Developed by: Hydrologic Engineering Center (CEIWR-HEC), United States Corps of Engineers (USACE)Institute for Water Resources
  
Date:  
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Date: July 1995
  
 
Type: [[:Category:Tools|Tool]]
 
Type: [[:Category:Tools|Tool]]
  
Suitable for the following [[::Category:Measures|measures]]:
 
 
=Introduction=
 
=Introduction=
HEC-RAS (Hydrologic Engineering Center-River Analysis System) is a freely available and widely used software tool for open channel flow analysis. The first version of the software, originally developed as a one-dimensional (1D) open channel flow analysis tool, was released in July 1995. In 2016 the ability to perform two-dimensional (2D) modelling was added. The current version allows users to perform 1D steady flow and 1D/2D unsteady flow modelling, sediment transport/mobile bed computations, and water temperature/water quality modelling for a full network of natural and constructed channels, or a single river reach, under the same graphical user interface (GUI) (Figure 1).
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HEC-RAS (Hydrologic Engineering Center-River Analysis System) is a freely available and widely used software tool for open-channel flow analysis. The first version of the software, originally developed as a one-dimensional (1D) open-channel flow analysis tool, was released in July 1995. In 2016 the ability to perform two-dimensional (2D) modelling was added. The current version allows users to perform 1D/2D unsteady flow modelling, sediment transport/mobile bed computations, and water temperature/water quality modelling for a full network of natural and constructed channels, or a single river reach, under the same graphical user interface (GUI) (Figure 1).
  
The basic computational procedure of HEC-RAS for steady flow is based on the solution of the 1D energy equation, the energy losses are evaluated by friction (Manning’s equation) and contraction/expansion (coefficient multiplied by the change in velocity head). The momentum equation may be used in situations where the water surface is rapidly varied (e.g. hydraulic jumps, bridges, river confluences). For the 1D unsteady flow computation, HEC-RAS solves the full, dynamic, 1D Saint Venant Equation using an implicit finite difference method. For the 2D modelling the software solves either the 2D Saint Venant equations, often referred to as the shallow water equations (with optional momentum additions for turbulence and Coriolis effects) or the 2D Diffusion Wave equations. This is user-selectable, giving modellers more flexibility. The shallow water equations solver disregards vertical velocities and assumes hydrostatic pressure, whereas the diffusive wave approximation solver additionally omits unsteady, advection and turbulent viscous terms, which narrows the range of applicability but has many computational advantages. Thus, in general, selection of the 2D Diffusion Wave equations allows the software to run faster, and has greater stability properties, whereas the 2D Saint-Venant equations are applicable to a wider range of problems.
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The basic computational procedure of HEC-RAS for steady flow is based on the solution of the 1D energy equation. The friction energy losses are computed by Manning’s equation, and the contraction/expansion head losses by coefficients multiplied by the change in velocity head. The momentum equation may be used in situations where the water surface is rapidly varied (e.g. hydraulic jumps, bridges, river confluences). For the 1D unsteady flow computation, HEC-RAS solves the full 1D Saint-Venant equation using an implicit finite difference method. For the 2D modelling the software solves either the 2D Saint- Venant equations, often referred to as the shallow water equations (with optional momentum additions for turbulence and Coriolis effects) or the 2D diffusion wave equations. This is user-selectable, giving users more flexibility. The shallow water equations solver disregards vertical velocities and assumes hydrostatic pressure, whereas the diffusive wave approximation solver additionally omits unsteady, advection and turbulent viscous terms, which narrows the range of applicability but has many computational advantages. Thus, in general, selection of the 2D diffusion wave equations allows the software to run faster, and has greater stability properties, whereas the 2D Saint-Venant equations are applicable to a wider range of problems.
 
The 2D unsteady flow equations solver uses an Implicit Finite Volume algorithm. The implicit solution algorithm allows for larger computational time steps than explicit methods. The Finite Volume method guarantees improved stability and robustness over traditional finite difference and finite element techniques with the wetting and drying of 2D cells being very robust.  
 
The 2D unsteady flow equations solver uses an Implicit Finite Volume algorithm. The implicit solution algorithm allows for larger computational time steps than explicit methods. The Finite Volume method guarantees improved stability and robustness over traditional finite difference and finite element techniques with the wetting and drying of 2D cells being very robust.  
  
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The 2D modelling has a flexible mesh generation allowing the user to generate a computation grid that is a mixture of structured and unstructured mesh types with the possibility of containing a mixture of cell shapes (the model is limited to elements with up to eight sides) and sizes. A user can customize a mesh to suit the terrain, containing predominantly large orthogonal grid cells (which simplifies the numerical discretization, making it more efficient), and where needed smaller cells, orientated appropriately along controlling terrain such as road crests, or along important river channels.
 
The 2D modelling has a flexible mesh generation allowing the user to generate a computation grid that is a mixture of structured and unstructured mesh types with the possibility of containing a mixture of cell shapes (the model is limited to elements with up to eight sides) and sizes. A user can customize a mesh to suit the terrain, containing predominantly large orthogonal grid cells (which simplifies the numerical discretization, making it more efficient), and where needed smaller cells, orientated appropriately along controlling terrain such as road crests, or along important river channels.
  
Within HEC-RAS each computational cell and cell face is based on the details of the underlying terrain, which is referred to as “high resolution subgrid model”. This allows larger cell sizes without compromising the resolution of the results, since it still accurately represents the underlying terrain, with gains in the modelling time.
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In HEC-RAS, each computational cell and cell face is based on the details of the underlying terrain, which is referred to as ''high resolution subgrid model''. This allows larger cell sizes without compromising the resolution of the results, since it still accurately represents the underlying terrain, with gains in the modelling time.
  
 
=Application=
 
=Application=
CASiMiR integrates interfaces for several 2D hydrodynamic models such as Hydro-AS_2D, SRH, BASEMENT, FLUMEN, River2D. The model has been applied in rivers of most different dimensions, types and stretches with lengths between several 10 meters to sections of several dozens of kilometres length (Figure 4).  
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HEC-RAS has a wide range of applications; it can be applied to river/open-channel flow analysis, river rehabilitation/restoration studies, floodplain determination studies, hydraulic structures design and analysis (e.g. bridges, weirs, culverts), sediment transport studies, scour/deposition analysis, dam break analysis (e.g. timing of flood, flood inundation), and water quality analysis.
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As input data, it requires geometry data, like topography (e.g. surveyed cross sections, digital elevation model), energy losses (e.g. roughness, expansions and contractions), and hydraulic structures (e.g. bridges, culverts, weirs). Hydrology data (e.g. gauging stations data, measured/observed flow and water depth data) are also needed for calibration/validation and/or boundary conditions. If sediment transport or water quality studies are intended, sediment data (e.g. representative material, appropriate transport equations, appropriate sorting and fall velocity methods) and water quality data (e.g. meteorological data, nutrients data) are required, respectively.
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HEC-RAS has an internal GIS tool (RAS Mapper) which provides flexible viewing and manipulation of integrated 1D and 2D results, greatly enhancing the pre- and post-processing capabilities of data within the software.
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Outputs of HEC-RAS include graphics, like X-Y plots of the river system schematic, cross-sections (Figure 2), profiles (Figure 3), rating curves (Figure 4), hydrographs (Figure 5), and inundation mapping (Figure 6). Inundation maps can contain multiple background layers, like terrain and aerial photography, and additional geospatial data can be generated for the analysis of velocity, shear stress, stream power, ice thickness and floodway encroachment data. Tabular output (Figure 7) is available with the possibility of selecting pre-defined tables or developing customized tables. The graphical and tabular output can be exported to other software, such as a word-processor or a spreadsheet.
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The current version (5.0.7) cannot perform sediment transport and water quality modelling in 2D flow areas, nor use HEC-RAS bridge modelling capabilities inside of a 2D flow area, nor connect pump stations to 2D flow area cells.
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=Relevant mitigation measures and test cases=
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{{Suitable measures for HEC-RAS}}
  
CASiMiR is unique in that it makes use of physical and biological parameters through the application of expert knowledge using fuzzy logic-based rule systems, but can also use the standard preference function method as well. The main advantages of using habitat simulation models are:
 
*The ecological condition of an aquatic ecosystem is directly coupled with the living conditions of the typical resident species.
 
*The use of habitat models allows for the effects of changing flow rates and structural characteristics to be account for and can be used to predict their impacts.
 
*Changes to the flow rate and morphology result primarily in impacting the water depth, flow velocity, and substrate conditions, all of which are major factors in determining the habitat suitability and can be directly evaluated with numerical models.
 
*Due to the direct relationship between habitat conditions and flow rate, a quantitative basis can be established whereby an overall ecological assessment of the habitat requirements can be performed.
 
 
=Other information=
 
=Other information=
Base versions of CASiMiR are free for download under http://www.casimir-software.de. Advanced versions can be purchased via mailbox@sjeweb.de. Scientific and commercial licenses are available.
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HEC-RAS is freely available at: https://www.hec.usace.army.mil/software/hec-ras/.
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Since the software is continuously under development, users are encouraged to submit suggestions and requests for enhancement, or to report bugs or possible errors, so current limitations and new additions are worked on to have solutions and improvements in future versions.
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The 2D modelling is done with a multi-processor based solution algorithm (parallel computing), to take advantage of multiple processors on a computer, allowing it to run much faster than on a single processor.
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HEC-RAS is compatible with several GIS software. HEC-GEO-RAS is an extension for ArcGIS which allows for the pre-processing of geometric data to import to HEC-RAS and the post-processing of the results. It was developed by CEIWR-HEC together with ESRI (Environmental System Research Institute). RiverGIS is a QGIS plug-in for creating HEC-RAS flow model geometry from spatial data, and is a free software released under the GNU General Public License.
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=Relevant literature=
 
=Relevant literature=
*Noack, M., Schneider, M. and Wieprecht, S. (2013): The Habitat Modelling System CASiMiR: A Multivariate Fuzzy Approach and its Applications; in Ecohydraulics: An Integrated Approach, Chapter 6 (75-93); Editors I. Maddock, A. Harby, P. Kemp, P. Wood, John Wiley & Sons Ltd
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*https://www.hec.usace.army.mil/software/hec-ras/
*Schneider, M., Kopecki, I., Tuhtan, J., Sauterleute, J., Zinke, P., Bakken, T., Zakowski, T., Merigoux, S. (2016): A Fuzzy Rule-based Model for the Assessment of Macrobenthic Habitats under Hydropeaking Impact. River Research and Applications, 1467-1535
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*https://www.hec.usace.army.mil/software/hec-ras/documentation.aspx
*Kopecki, I., Tuhtan, J., Schneider, M., Ortlepp, J., Thonhauser, S., Schletterer, M. (2014): Assessing Fishway Attraction Flows Using an Ethohyraulic Approach. 3rd IAHR Europe Congress, Porto, April 14-16.
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=Contact information=
 
=Contact information=
http://www.casimir-software.de
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hec.ras@usace.army.mil
 
 
 
 
 
[[Category:Tools]]
 
[[Category:Tools]]

Latest revision as of 13:38, 29 September 2020

Quick summary

Figure 1: HEC-RAS graphical user interface (GUI) (source: https://www.hec.usace.army.mil/software/hec-ras/).
Figure 2: HEC-RAS output: cross sections (source: https://www.hec.usace.army.mil/software/hec-ras/).
Figure 3: HEC-RAS output: river profiles (source: https://www.hec.usace.army.mil/software/hec-ras/).
Figure 4: HEC-RAS output: rating curve (source: https://www.hec.usace.army.mil/software/hec-ras/).
Figure 5: HEC-RAS output: hydrograph and stage(source: https://www.hec.usace.army.mil/software/hec-ras/).
Figure 6: HEC-RAS output: inundation mapping (source: https://www.hec.usace.army.mil/software/hec-ras/).
Figure 7: HEC-RAS output: tabular output (source: https://www.hec.usace.army.mil/software/hec-ras/).

Developed by: Hydrologic Engineering Center (CEIWR-HEC), United States Corps of Engineers (USACE)Institute for Water Resources

Date: July 1995

Type: Tool

Introduction

HEC-RAS (Hydrologic Engineering Center-River Analysis System) is a freely available and widely used software tool for open-channel flow analysis. The first version of the software, originally developed as a one-dimensional (1D) open-channel flow analysis tool, was released in July 1995. In 2016 the ability to perform two-dimensional (2D) modelling was added. The current version allows users to perform 1D/2D unsteady flow modelling, sediment transport/mobile bed computations, and water temperature/water quality modelling for a full network of natural and constructed channels, or a single river reach, under the same graphical user interface (GUI) (Figure 1).

The basic computational procedure of HEC-RAS for steady flow is based on the solution of the 1D energy equation. The friction energy losses are computed by Manning’s equation, and the contraction/expansion head losses by coefficients multiplied by the change in velocity head. The momentum equation may be used in situations where the water surface is rapidly varied (e.g. hydraulic jumps, bridges, river confluences). For the 1D unsteady flow computation, HEC-RAS solves the full 1D Saint-Venant equation using an implicit finite difference method. For the 2D modelling the software solves either the 2D Saint- Venant equations, often referred to as the shallow water equations (with optional momentum additions for turbulence and Coriolis effects) or the 2D diffusion wave equations. This is user-selectable, giving users more flexibility. The shallow water equations solver disregards vertical velocities and assumes hydrostatic pressure, whereas the diffusive wave approximation solver additionally omits unsteady, advection and turbulent viscous terms, which narrows the range of applicability but has many computational advantages. Thus, in general, selection of the 2D diffusion wave equations allows the software to run faster, and has greater stability properties, whereas the 2D Saint-Venant equations are applicable to a wider range of problems. The 2D unsteady flow equations solver uses an Implicit Finite Volume algorithm. The implicit solution algorithm allows for larger computational time steps than explicit methods. The Finite Volume method guarantees improved stability and robustness over traditional finite difference and finite element techniques with the wetting and drying of 2D cells being very robust.

The 1D and 2D solution algorithms are tightly coupled on a time step basis with an option to iterate between 1D and 2D flow transfers within a time step. This allows for direct feedback at each time step between the 1D and 2D flow elements.

The 2D modelling has a flexible mesh generation allowing the user to generate a computation grid that is a mixture of structured and unstructured mesh types with the possibility of containing a mixture of cell shapes (the model is limited to elements with up to eight sides) and sizes. A user can customize a mesh to suit the terrain, containing predominantly large orthogonal grid cells (which simplifies the numerical discretization, making it more efficient), and where needed smaller cells, orientated appropriately along controlling terrain such as road crests, or along important river channels.

In HEC-RAS, each computational cell and cell face is based on the details of the underlying terrain, which is referred to as high resolution subgrid model. This allows larger cell sizes without compromising the resolution of the results, since it still accurately represents the underlying terrain, with gains in the modelling time.

Application

HEC-RAS has a wide range of applications; it can be applied to river/open-channel flow analysis, river rehabilitation/restoration studies, floodplain determination studies, hydraulic structures design and analysis (e.g. bridges, weirs, culverts), sediment transport studies, scour/deposition analysis, dam break analysis (e.g. timing of flood, flood inundation), and water quality analysis.

As input data, it requires geometry data, like topography (e.g. surveyed cross sections, digital elevation model), energy losses (e.g. roughness, expansions and contractions), and hydraulic structures (e.g. bridges, culverts, weirs). Hydrology data (e.g. gauging stations data, measured/observed flow and water depth data) are also needed for calibration/validation and/or boundary conditions. If sediment transport or water quality studies are intended, sediment data (e.g. representative material, appropriate transport equations, appropriate sorting and fall velocity methods) and water quality data (e.g. meteorological data, nutrients data) are required, respectively.

HEC-RAS has an internal GIS tool (RAS Mapper) which provides flexible viewing and manipulation of integrated 1D and 2D results, greatly enhancing the pre- and post-processing capabilities of data within the software.

Outputs of HEC-RAS include graphics, like X-Y plots of the river system schematic, cross-sections (Figure 2), profiles (Figure 3), rating curves (Figure 4), hydrographs (Figure 5), and inundation mapping (Figure 6). Inundation maps can contain multiple background layers, like terrain and aerial photography, and additional geospatial data can be generated for the analysis of velocity, shear stress, stream power, ice thickness and floodway encroachment data. Tabular output (Figure 7) is available with the possibility of selecting pre-defined tables or developing customized tables. The graphical and tabular output can be exported to other software, such as a word-processor or a spreadsheet.

The current version (5.0.7) cannot perform sediment transport and water quality modelling in 2D flow areas, nor use HEC-RAS bridge modelling capabilities inside of a 2D flow area, nor connect pump stations to 2D flow area cells.

Relevant mitigation measures and test cases

Relevant measures
Bypass combined with other solutions
By-passing sediments
Cleaning of substrate - ripping, ploughing and flushing
Complete or partial migration barrier removal
Construction of a 'river-in-the-river'
Construction of off-channel habitats
Environmental design of embankments and erosion protection
Migration barrier removal
Mitigating rapid, short-term variations in flow (hydro-peaking operations)
Mitigating reduced annual flow and low flow measures
Mitigating reduced flood peaks, magnitudes, and frequency
Nature-like fishways
Other types of fine screens
Placement of dead wood and debris
Placement of spawning gravel in the river
Placement of stones in the river
Removal of weirs
Restoration of the riparian zone vegetation
Sediment sluicing
Vertical slot fishways
Relevant test cases Applied in test case?
Altheim test case -
Altusried test case -
Anundsjö test case -
Bannwil test case -
Bragado test case Yes
Freudenau test case -
Gotein test case -
Guma and Vadocondes test cases Yes
Günz test case -
Ham test case -
Las Rives test case -
Schiffmühle test case -
Trois Villes test case -

Other information

HEC-RAS is freely available at: https://www.hec.usace.army.mil/software/hec-ras/. Since the software is continuously under development, users are encouraged to submit suggestions and requests for enhancement, or to report bugs or possible errors, so current limitations and new additions are worked on to have solutions and improvements in future versions.

The 2D modelling is done with a multi-processor based solution algorithm (parallel computing), to take advantage of multiple processors on a computer, allowing it to run much faster than on a single processor.

HEC-RAS is compatible with several GIS software. HEC-GEO-RAS is an extension for ArcGIS which allows for the pre-processing of geometric data to import to HEC-RAS and the post-processing of the results. It was developed by CEIWR-HEC together with ESRI (Environmental System Research Institute). RiverGIS is a QGIS plug-in for creating HEC-RAS flow model geometry from spatial data, and is a free software released under the GNU General Public License.

Relevant literature

Contact information

hec.ras@usace.army.mil