SMS:SRH-2D

SRH-2D
Model Info
Model type	Two-dimensional (2D) hydraulic, sediment, temperature, and vegetation model for river systems
Developer	Yong Lai Bureau of Reclamation
Web site	SRH-2D web site
Tutorials	General Section Data Visualization Mesh Editing Observation Models Section SRH-2D (Pending)

SRH-2D, or the Sedimentation and River Hydraulics – Two-Dimensional model, is a two-dimensional (2D) hydraulic, sediment, temperature, and vegetation model for river systems under development at the Bureau of Reclamation. It was known as SRH-W in version 1, and the name was changed to the current SRH-2D from version 2 onward.

Currently, it is recommended that the SRH-2D model only be used with the 64-bit version of SMS. Errors may occur if using the 32-bit version.

Features

• SRH-2D solves the 2D depth-averaged form of the diffusive wave or the dynamic wave equations. The dynamic wave equations are the standard St. Venant depth-averaged shallow water equations
• Both the diffusive wave and dynamic wave solvers use the implicit scheme to achieve solution robustness and efficiency
• Both steady or unsteady flows may be simulated
• All flow regimes, i.e., subcritical, transcritical, and supercritical flows, may be simulated simultaneously without the need of a special treatment
• Solution domain may include a combination of main channels, side channels, floodplains, and overland
• Solved variables include water surface elevation, water depth, and depth averaged velocity. Output information includes above variables, plus flow inundation, Froude number, and bed shear stress

SRH-2D is a 2D model and it is particularly useful for problems where 2D effects are important. Examples include flows with in-stream structures, through bends, with perched rivers, with multiple channel systems, and with complex floodplains. A 2D model may also be needed if one is interested in local flow velocities, eddy patterns and flow recirculation, lateral variations, flow spills over banks and levees, and flow diversion and bifurcation.

The Bureau of Reclamation does not provide technical support for SRH-2D.

Graphical Interface

SRH-2D uses a custom interface to specify boundary conditions, model paramters, model control and material parameters. The interface includes the following:

• SRH Menu
• SRH Model Control
• SRH Material Properties – SRH is able to work with a number of material zones. Materials may be created from a Materials Coverage, an SRH coverage, or directly from the mesh. Materials are added by selecting Edit | Materials Data when the coverage or mesh is activated.
• SRH Monitor Points Coverage
• SRH file I/O – When a user wishes to execute an SRH-2D model, he/she should export the model native files using the Export SRH-2D Files or Save/Export/Launch commands in the SRH-2D menu. The native files include:

• SRHHYDRO – Contains key information about the simulation while acting as a directory to other files for SRH to use.
• SRHGEOM – Tells SRH where each element is located and the characteristics of that element.
• SRHMAT – Gives each element a material type.
• SRHMONITORPTS – Tells SRH that there are monitor points to watch and where those points are located.

In the past, this model has been utilized through the Generic Model Graphical Interface. The SRH-2D version 2.0 Distribution included SRH2D template files for both SMS 8.0 and SMS 10.0. These are no longer needed with the custom interface.

Steps to Create an SRH-2D Model

To create an SRH model, the following general steps should be followed:

1. Gather data pertinent to the project and location. This should include bathymetry data, roughness data (Manning's n value), coordinate system corresponding to the data, and flow data.
2. Specify a coordinate system. This is done in the Disply Projections dialog accessed through the Display menu.
3. Add bathymetry data. This may come as survey data, Lidar data, or Raster DEM data to name a few.
4. Check the triangulation or raw data display. It is important to make sure that SMS is reading the data the same way that it was measured. Turning on contours will allow the user to view what SMS sees and make adjustments as needed. Contours may be turned on using the Display Options command. Optionally, the user may use the tools available in SMS for refinement of the data.
5. Create coverages. A simple SRH project would likely include a SRH-2D main coverage which would hold data about mesh type and bythymetry data, a materials coverage, which would map material types to region, and a monitor points coverage which will hold data relating to specific locations where site specific data will be gathered. Coverages may be created by right-clicking on the map data folder from the data tree and selecting New Coverage. The coverage is assigned a type upon creation. For an SRH model, select the SRH coverages as they relate to the data that will correspond to that type.
6. Outline the workspace with arcs. Here the user is defining regions of the model location that will have unique features. For example, locations of more water interaction will need more detail which equates to more nodes; locations with different roughness values will need to be separated for material type assignments. Create polygons for areas of similar characteristics. Keep in mind that SMS has a variety of tools available to adjust the arcs to meet the modeling needs of the project.
7. Build polygons.
8. Assign attributes to the polygons. Direct SMS to what materials and what mesh type is to be built over that polygon. Specify how SMS should assign elevation data by selecting the bathymetry source
9. Assign attributes to the arcs by giving the arcs boundary conditions. For interior arcs, the only option is a monitor line. For exterior arcs the user may choose from a variety of inlet conditions, whether subcritical or supercritical, as well as outlet or water surface elevation options. For no flow boundaries, the option of a wall or symmetry is available.
10. Prepare to build the mesh. Review the information given to SMS to ensure that the field data matches what is represented virtually for the region. After a review of the inputs for the model, the mesh is ready to be built. The mesh is built by converting the Map coverage to a 2D Mesh.
11. Build the mesh. If all of the attributes for the arcs and polygons were assigned correctly, the mesh will represent the same data over the elements and nodestrings. If the data is incomplete or changes need to be made, they will need to be done on the elements (for material properties) or the nodestrings (for boundary conditions). Note, that if necessary, it is possible to delete the mesh and adjust values over the polygons and arcs before regenerating the mesh.
12. Run the model. First, be sure that the project is saved. Next, from the SRH-2D menu, select Export SRH. Finally, from the SRH-2D menu, select Launch SRH.
13. Analysis of results and post processing.

Releases

Version 1

SRH-W, or Sedimentation and River Hydraulics - Watershed, is a two-dimensional (2D) hydraulic model for river systems and watersheds developed at the Bureau of Reclamation. SRH-W was originally developed for Reclamation internal use for various projects, and version 1.1 was released for public use.

SRH-W v1.1 is used for hydraulic flow simulation in rivers and runoff from watersheds, but without the sediment capability. It solves the 2D dynamic wave equations (the standard depth-averaged St. Venant equations) that are mainly used for river simulation. In addition, the diffusive wave solver is used for watershed runoff simulation and river simulation.

Version 1.1 is comparable to many existing models such as RMA-2 (US Army Corps of Engineers, 1996) and MIKE 21 (DHI software, 1996) in its river simulation capability. For watershed applications, SRH-W v1.1 is a distributed model for event based runoff simulation and has capabilities similar to CASC2D (Julien, et al, 1995).

Version 2

In Version 2, SRH-W was renamed to SRH-2D. Version 2 solves the 2D dynamic wave equations, i.e., the depth-averaged St. Venant equations. Its modeling capability is comparable to some existing 2D models but SRH-2D claims a few boasting features. First, SRH-2D uses a flexible mesh that may contain arbitrarily shaped cells. In practice, the hybrid mesh of quadrilateral and triangular cells is recommended though purely quadrilateral or triangular elements may be used. A hybrid mesh may achieve the best compromise between solution accuracy and computing demand. Second, SRH-2D adopts very robust and stable numerical schemes with a seamless wetting-drying algorithm. The resultant outcome is that few tuning parameters are needed to obtain the final solution. SRH-2D was evolved from SRH-W which had the additional capability of watershed runoff modeling. Many features are improved from SRH-W.

Major Features of Version 2

Major SRH-2D capabilities are listed below

• 2D depth-averaged dynamic wave equations (the standard St. Venant equations) are solved with the finite-volume numerical method
• Steady state (with constant discharge) or unsteady flows (with flow hydrograph) may be simulated
• An implicit scheme is used for time integration to achieve solution robustness and efficiency
• An unstructured arbitrarily-shaped mesh is used which includes the structured quadrilateral mesh, the purely triangular mesh, or a combination of the two. Cartesian or raster mesh may also be used. In most applications, a combination of quadrilateral and triangular meshes is the best in terms of efficiency and accuracy
• All flow regimes, i.e., subcritical, transcritical, and supercritical flows, may be simulated simultaneously without the need for special treatments
• Robust and seamless wetting-drying algorithm; an
• Solved variables include water surface elevation, water depth, and depth averaged velocity. Output variables include the above, plus Froude number, bed shear stress, critical sediment diameter, and sediment transport capacity.

SRH-2D is a 2D model, and it is particularly useful for problems where 2D effects are important. Examples include flows with in-stream structures, through bends, with perched rivers, with side channel and agricultural returns, and with braided channel systems. A 2D model may also be needed if one is interested in local flow velocities, eddy patterns, flow recirculation, lateral velocity variation, and flow over banks and levees.

Version 3

SRH-2D version 3 is the current version.

Version 4

Version 4 is not yet released.

External Links

• Bureau of Reclamation SRH-2D Website

External Links – SRH-2D Version 2.0

• SRH-2D version 2.0 Theory and User Manual
• SRH-2D version 2.0 Distribution – Includes Software, Manual, Template file for integration into SMS interface, and Tutorials

Papers / Presentations

• SRH-2D Theory Paper
• SRH-2D Training Presentation
• 2005 US-China Workshop Paper[1]
• 2006 FISC Paper on Savage Rapids Dam Removal Project - "Comparison of Numerical Hydraulic Models Applied To The Removal of Savage Rapids Dam Near Grants Pass, Oregon"
• FISC 2006 Short Course Presentation
• Using Bathymetric LiDAR and a 2-D Hydraulic Model to Identify Aquatic River Habitat
• List of journal articles using SMS by Prof. Greg Pasternack, UC Davis

Project Reports

• Bountry J.A. and Lai, Y.G. (2006)."Numerical modeling of flow hydraulics in support of the Savage Rapids Dam removal."
• Lai, Y.G., Holburn, E.R., and Bauer, T.R. (2006)."Analysis of sediment transport following removal of the Sandy River Delta Dam."
• Lai, Y.G. and Bountry, J.A. (2006). "Numerical hydraulic modeling and assessment in support of Elwha Surface Diversion Project."
• Lai, Y.G. and Bountry, J.A. (2007). "Numerical modeling study of levee setback alternatives for lower Dungeness River, Washington"

In the News

• Wired.com article "Computer Modeling Smoothes a Dam Hard Job"
• Photos related to Wired.com article "Computer Modeling Smoothes a Dam Hard Job"

External Links – SRH-W

SRH-W Version 1.1

• SRH-W version 1.1 User Manual
• SRH-W version 1.1 Distribution Package – Includes Software, Manual, and Tutorials

Papers / Presentations

• 2006 FISC Watershed Modeling Paper - Watershed Simulation with an Enhanced Distributed Model[2]

Related Topics

• SMS Models