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FM Tute M01 ARC 1D2D Links: Difference between revisions

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Depending on the water level in the surrounding 2D cells, flow can either enter or leave the HX cells. The volume of water entering or leaving the 2D boundary is added or subtracted from the 1D Flood Modeller model to preserve volume. We must connect the HX lines to the 1D Flood Modeller model. This is done using CN type lines in the 2d_bc layer, where a CN line is connected to the HX line, the water level from the 1D Flood Modeller nodes is transferred to the HX line. In between 1D nodes, a linear interpolation of water level is applied. This is shown in the figure below.
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[[File:1d 2d FM link 01.jpg|800px]]
'''INSERT FIGURE'''
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AsOnce the water level in theFlood 2DModeller isexceeds calculatedthe atelevation in the boundary cell centres,water oncecan enter or leave the watermodel. levelSimilar into a Flood Modeller exceedslateral spill or lateral inflow, the discharge is distributed laterally along the length of the HX line. Note that it is the elevation inof the HX boundary cell watercentres canthat enterdetermines orwhen leavethe spill starts to occur and not the model.cross section within Flood Modeller. If there is a levee or flood defence, it is important that we use breaklines in the model to ensure that the elevations of the 2D cells are consistent with the levee crest. This will be described in the next section of the tutorial. The next four images show a section view of the 1D/2D link and how this may progress during a flood event.<br>
 
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[[File:M04 1d2d 01.png|300px]]
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In the example below, the HX lines are broken between FC01.35 and FC01.34 as a culvert is located between these nodes.
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[[File:FMTFM 1D-2D Broken HX FMJunction.JPG|900px]] [[File:FMT 1D-2D Broken HX.JPG|900px]]
 
<li>The CN and HX lines between nodes FC02.06 and FC02.01d along the tributary have not been digitised. Digitise these lines to connect the nodes to the 2D domain.<br>
To digitise the CN lines, make the <b> 2d_bc_FMT_M01_HX_001_L.SHP </b> layer editable and ensure snapping is turned on. For each node in the '''1d_x1d_FMT_M01_nodes_001_P.SHP''' layer, draw a line from the node to the HX line. The line must snap to both the node and the HX line. Draw two lines for each node, one to the left bank and one to the right bank. In the 'Type' attribute of each line, type 'CN'. Assign the digitised CN lines an ‘f' attribute’ of ‘1’. This sets the weighting to be applied in distributing the water level from the 1D node to the 2D cell. <br>
<br>The figure below shows how the nodes are connected at the confluence. Note that all Flood Modeller nodes at the junction are present within the 1d_x1D_nodes layer, and are connected to the 2D domain. The HX lines are broken around the junction. </li>
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