Difference between revisions of "SMS:TUFLOW Coverages"

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Revision as of 21:06, 16 September 2009

TUFLOW models use several types of Feature coverages. Feature coverages are used in SMS to represent geometry and associated attributes as points, arcs, and polygons. Unlike most models used in SMS, TUFLOW uses coverage data as model inputs.

TUFLOW coverages can be associated with 2D Geometry Components and TUFLOW Simulations by creating links to the coverage in the component or simulation. The use of links allows multiple simulations or geometry components to share coverage data. Sharing data between simulations reduces required disk space for the simulation and makes it easier to update several simulations with the same changes.

In addition to the coverages listed below, TUFLOW models can use Area Property Coverages to define where to use specific material properties using polygons.


1D/2D Connections Coverage

1D/2D connections are used with the 2D BC coverage (see ****) to link 2D and 1D domains. See (***** linking 1D and 2D models).

Two types of arcs can be created in a 1D/2D connection coverage: 1D/2D connection arcs (CN) and Flow vs. Head Connection arcs (SC).

1D/2D Connection arcs are written to a 2d_bc layer file for TUFLOW input (see 2d_bc_layers in the TUFLOW documentation). One end of the connection arcs must end at the same location as a 1D Flow/2D Water Level Connection (HX) in a TUFLOW BC coverage. The other end of the connection arc must end at the same location as a network node in a TUFLOW network coverage.

2D/2D Links Coverage

A 2D/2D Links Coverage is used to setup TUFLOW to use multiple 2D domains. See Linking 2D Domains.

Boundary Conditions Coverage

Boundary conditions are defined in TUFLOW with points, arcs, or polygons in a BC coverage. BC coverages can also be used to specify cell code (active/inactive) areas of the 2D model domain. The kinds of boundary conditions available depend upon whether it is applied to a point, arc or polygon.

Boundary conditions defined at points are 1D boundary conditions and must be placed at the same location as a 1D boundary node. (See Snapping Feature Objects) The boundary condition information is specified in the BC Node Attributes Dialog (see BC Node Attributes Dialog).

Arcs can be used to define 2D Boundary conditions applied to the 2D domain. The BC attributes are specified in the BC Arc Attributes Dialog (see BC Arc Attributes Dialog).

Polygons can be used to define rainfall applied to 2D domains or to specify active/inactive information for 2D domains. The BC Polygon Attributes dialog specifies the type of information stored with the polygons (see BC Polygon Attributes Dialog).

1D Cross Section Coverage

Cross section coverages are used to define open channel cross section data for 1D networks. Cross section geometry is generally extracted from a TIN and may be edited by hand if desired.

Cross sections are created by creating arcs in a cross section coverage. SMS can automatically create cross section arcs from a 1D network.

After cross section arcs are created, the elevations for the arc can be extracted from a scatter set (TIN) by right clicking on the coverage and selecting “Extract from Scatter” from the menu. This will extract the cross-section data from the active dataset on the active scatter set. Values are extracted at each triangle edge in the scatter set and each node or vertex on the cross section arc.

After cross sections have been created, the materials from an area property coverage may be mapped to the cross-sections. This is done by right clicking on the coverage and selecting, “Map Materials from Area Property Coverage.”

Individual Cross sections may be viewed and edited by double clicking on an arc, or by selecting an arc and choosing Feature Objects->Attributes. This will bring up the cross-section attributes dialog (see TUFLOW Cross Section Attributes).

All the cross-sections in the coverage are stored in a cross section database. The cross section database may be opened by right clicking on the coverage and selecting “Properties” (see Editing Cross Sections).

2D Geometry Modification Coverage

TUFLOW Geometry Modification Coverages are used to force grid elevation values using arcs or polygons. This can be useful to ensure ridge or gulley lines are represented in the model, simulate a proposed levy, or to simulate a proposed fill/excavation scenario.

It is possible to only have the elevations assigned from a feature object if the feature elevation is higher or lower (user specified) than the existing elevations in the grid. This is controled in the 2D Geometry Modification Coverage Properties (right click on the coverage and choose Properties).

Make sure the coverage is in the Geometry Component(s) you wish to apply to the modification to.

Points

Points are ignored in the geometry modification coverage.

Arcs

Only the elevations at the nodes (endpoints) are used to set the grid elevations. Vertex (intermediate) elevations are ignored. Cell elevations along the arc will be interpolated linearly based on distance from the endpoint elevation. If you would like to specify elevations at vertices on an arc, convert the arc vertices to nodes to create multiple arcs joined end to end.

Polygons

To set the elevation for polygons double click on the polygon and enter the elevation in the dialog. This elevation will be applied to all cells within the polygon.

Z Shape Coverage

The Z shape coverage is similar to the geometry modification coverage but has additional options. With the ZShape coverage, you can even modify geometry through time to simulate levee failures or other changes to elevation data within the model run.

'Make sure the coverage is in the Geometry Component(s) you wish to apply to the modification to.

Grid Extents Coverage

A TUFLOW Grid Extents coverage is used to create TUFLOW grids. TUFLOW grids are created by creating and positioning a Cartesian Grid Frame and then right clicking on the coverage and choosing Map->2D Grid.

1D Network Coverage

1D domains are made up of a network of channels and nodes. Channels represent the conveyance of the flowpaths and nodes represent the storage of inundated areas (TUFLOW Users Manual). Channels are created using arcs and the arc endpoints are the nodes.

There are a variety of channel types including open channels, weirs, and culverts (pipe networks). The channel also has a variety of attributes depending upon the channel type. The channel type and attributes are defined in the Channel Attributes dialog.

There are two types of nodes generic nodes, and inlets. Generic nodes can be used to specify storage and can be used to set channel invert elevations. Inlet nodes are used to get flows from a 2D domain into a 1D pipe network below the 2D domain. The node type and attributes are defined in the Network Node Attributes dialog. The TUFLOW documentation sections 4.5.1.3: Connecting Pits and Nodes to 2D Domains and 4.5.3: 1d_nwk Attributes list some new TUFLOW features that SMS now supports. SMS's Network Node Attributes dialog has several new additions to the Create Connection to 2D Domain (SX) section. These new options allow you to control elevations at the connections, how many cells are connected, and the method for selection of additional cells (Grade or Sag). Each option correlates fairly directly to a TUFLOW field and some are labeled as such to make lookup easy.

2D Spatial Attributes Coverage

Spatially varied attributes can be defined using the 2D spatial attributes coverage. The values for the attributes are assigned to polygons. TUFLOW assigns the values from the polygons to the cells that exist within the polygon.

The two available spatial attributes are initial water levels and weir factors.

Assigning spatially varied initial water levels may be necessary to ensure that water bodies have water in them initially.

Water Level Lines Coverage

Water level line coverages define the locations where 1D solutions will be written as 2D output. TUFLOW creates water level points along the water level lines. The water level lines in conjunction with the water level points guide TUFLOW on how to represent the 1D flow in the 2D domain.

Arcs are the only objects used in the water level lines coverage. The only attribute in the water level lines coverage is the minimum distance between water level points. This is used by TUFLOW to generate the water level points along the arcs.

For more information about how TUFLOW uses water level lines to generate 2D flows see TUFLOW Water Level Points Coverage.

Water Level Points Coverage

Water level points are used in conjunction with water level lines to guide TUFLOW on creating 2D output for 1D networks (see TUFLOW Water Level Lines Coverage).

Water level points store a material value. This material value along with the z location of each point is used by TUFLOW to better approximate 2D flow along a water level line. TUFLOW performs a parallel channel analysis so that flow rates reported in the 2D output vary based upon the depth and roughness of a channel. Areas that are more rough and shallow than other areas will have a smaller flow rate than other areas along the same water level line.

The material value for each point can be mapped from an area property coverage by right clicking on the coverage tree item and selecting “Materials for Area Coverage.” By default the elevation of each point is based upon the neighboring cross-section information.

Creating the Water Level Points Coverage

The initial water level points coverage data is created by TUFLOW during a run. Once a run has been completed, the data can be read from the check file that starts with the simulation name and ends with _WLLp_check.mif (see TUFLOW check files **Andrew Link). Open this file from SMS and select TUFLOW WLL Points from the combo-box that comes up. This coverage now can be included in simulations to provide additional guidance to TUFLOW in distributing 1D flows.