View source for Tute M04 Arc 1D2D Breaklines Archive

=Introduction=
In this section we will define within the model the elevation of the 2D cells activated by the HX lines we created in the previous step. The elevation of the HX activated cells control the flux between the 1D and 2D domains, and so it is important that the cell elevations reflect the true water level required for flow to cross the HX boundaries.
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As we have the HX lines in a 2d_bc format we can add the elevation points in the same format.  Alternatively, we could use the 2D Z Shape (2d_zsh) format that was used in module three of the tutorial.  If using this format it is important to ensure that a "thick" breakline format is used (by specifying a width greater than 0 and less than 1.5 times the cell size). 
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To create the breaklines we are going to convert the vertices along the "HX" lines to points and then sample the elevations from the DEM.  Another method would be to create a buffer (region) around each of these points and sample for the maximum elevation within the buffer.  This method is outlined in the following <u>[[Arc_Extract_Breakline_from_DEM | ArcGIS tip]]</u>.
=Method=
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<li>Select all the "'''HX'''" lines from the  '''2d_bc_M04_HX_001_L''' layer.  To do this use open the attribute table for the layer (right click on the layer in the Table of Contents and select ''Open Attribute Table''.  Use the select by attribute option to select all lines with "Type" equal to "HX".<br>
'''Tip: ''' Select the "TYPE" attribute and select ''Get Unique Values'' to get a list of values in the type column.</li>
<pre>"TYPE" = 'HX'</pre>.
[[File:Arc M04 2d breaklines 01.jpg|350px]]
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<li>To create points from these we need to save these as a separate table.  This will not be read into TUFLOW and can be deleted at the end of this step.  Save the selection as '''tmp_M04_HX_lines'''.  To export a selection as a new layer in ArcMap, right click on the layer in the table of contents and select ''Data >> Export Data''.<br>
In the export dialogue ensure that export '''Selected Features''' is selected.</li>
[[File:Arc M04 2d breaklines 02.jpg|400px]]
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<li>Next we need to convert the vertices along these lines to points.  This process uses the '''Feature Vertices To Points''' functionality. To open this select this from the toolbox.  This is located under Data Management >> Features >> Feature Vertices To Points.  Select the '''tmp_M04_HX_lines''' as the input layer (HX lines only). Once again this is a temporary file, set the output name as '''tmp_M04_HX_points'''and output this to the '''TUFLOW\model\gis\'''.<br>
To convert all vertices, use the default '''All''' option (alternate options include only the start or end vertices).</li>
[[File:Arc M04 2d breaklines 03.jpg|500px]]
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<li>Ensure the DEM ('''DEM_M01''') is open.</li>
<li>Once the points have been created we need to update the "TYPE" attribute to "'''ZP'''". This tells TUFLOW that the points contain elevation points.  To update the column, use the field calculator to update the "TYPE" attribute for <u>all</u> points to be "ZP".  Set the "FLAGS" to blank ("").</li>
<li> The next step is to inspect the elevations from the DEM.  To do this from the toolboxes select, ''Spatial Analyst >> Extraction >> Extract Values to Points''.</li>
[[File:Arc Extract Values to Points.jpg|300px]]
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<li>Set the input layer as the intermediate '''tmp_M04_HX_points''' layer containing the points and the input raster as the DEM.  Set the the output name as '''2d_bc_M04_HX_001_P'''and output this to the '''TUFLOW\model\gis\'''.  This output file will be inputted to TUFLOW.</li>
[[File:Arc M04 2d breaklines 04.jpg|500px]]
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<li>For elevation points contained in the 2d_bc format, we need to set the "'''f'''" attribute to the DEM column.  To update this, open the attribute table, right click on the "'''f'''" attribute and select ''Field Calculator''.</li>
<li>In the dialogue box simply double click on the raster value attribute.</li>
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=Conclusion=
The '''2d_bc_M04_HX_001_P''' which contains elevation points for the "HX" line has been created.  Please return to the tutorial where the next step is to <u>[[Tutorial_Module04_Archive#Deactivate_2D_Cells | deactivate the 2D cells in the creek areas.]]</u>