Tutorial M11 001 GIS Inputs QGIS GPKG: Difference between revisions

= Introduction =

QGIS is used to create, import and view input data.<br>

 

= Method =

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==1D Cross Section ==

A 1D open channel requires cross sections for processing of the channel geometry. For each cross section there is an individual comma separated csv file:

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<li>The cross sections extend further than the 2d_code layer and DEM, here the model transitions from a 1D/2D model to a 1D only model. This method can be used where cross section data is available but topography data is not.

<li>Use the 'Identify Features' tool to inspect a cross section line. Each line has a unique name in the 'Source' attribute field that links to a cross section csv contained within the '''xs''' folder. Type attribute 'XZ' specifies distance vs elevation cross section: <br>

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<li>Open the TUFLOW Viewer, the 1d_xs file automatically appears with a time series result 'XZ' showing. Select a 1d_xs line and view the cross section: <br>

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A 1d_nwk layer is used to model open channels. It contains information on inverts and to obtain data from the cross section the 1d_nwk and 1d_xs must be snapped:

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<li>There are three 1d_nwk types used:

:* S - standard open channel.

:* W - weir.

:* X - connecting channel used for side channels entering the main channel.

<li>Use the 'Identify Features' tool to inspect the attributes of the three 1d_nwk types:<br>

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The 1D model extents both upstream and downstream of the 2D active domain:

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<li>Use the 'Identify Features' tool to inspect the attributes of the three boundaries. A QT type (flow vs time) hydrograph is used to apply flow at the upstream boundary and a HQ (water level vs flow) boundary is used to remove flow from the downstream boundary based on a water level vs flow curve:<br>

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1D culverts are included in a separate 1d_nwk layer. 1D culverts are described in detail in <u>[https://wiki.tuflow.com/index.php?title=Tutorial_M03 Module 3]</u>:

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<li>There are two 1d_nwk types used:

:*C - circular culvert.

<li>Two culverts within the open channel link upstream 1D channel to the downstream 1D channel underneath the roads, the culvert to the east is embedded into the 2D domain directly. Use the 'Identify Features' tool to inspect the attributes:<br>

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The culvert on the east is connected to the 2D domain using 2d_bc layer SX type connection. It removes water out of the upstream cell(s) and deposits water back at the downstream cell(s):

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<li>The 2d_bc SX points are snapped to the 1d_nwk culvert:<br>

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The 1D open channel is linked to the 2D using a 2d_bc layer HX and CN type connections:

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<li>The 2d_bc HX type lines run along the top of bank. In HX type, the H indicates a head (water level) boundary and the X indicates a water level value coming from the 1D model. Once the water level in the 1D exceeds the water level in the 2D boundary cell, water can enter from 1D channel to 2D domain and vice versa. For water to flow in and out of floodplain overbank areas, HX lines extending into the floodplain at the upstream and downstream are required. Without them, the flow is assumed to be contained within bank which may not be the case.

<li>The CN lines connect the HX lines to the 1D channel. Where a CN line is connected to the HX line, the water level from the 1D nodes is transferred to the HX line. In between 1D nodes a linear interpolation of water level is applied. <br>

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[[File:2D Breaklines_all together.jpg|1200px]]<br>

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<li>The 2d_zsh line layer is used to define breaklines along the bank of the channel:

:*No ‘Z’ attribute is specified, the elevations are taken from the 2d_zsh point layer.

 

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The area of the 1D open channel defined by the 1D/2D HX boundaries must be removed from the active 2D cells:

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<li>The 2d_code layer is used to deactivate the area representing the 1D open channel with attribute of '0'. All cells within the polygon are removed from the 2D computations. <br>

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==Water Level Lines==

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<li>The 1d_wll layer must be digitised perpendicular to the flow direction and from left to right looking downstream. An attribute of '2.5' is specified for all lines as a minimum distance interval along the WLL to generate triangulation points. <br>

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<li>Select '0d_rl' from the Empty Type list.

<li>In the Run ID box write 'M11_001'.

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Copy the line and point from the 2d_po layer:

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<li>Right click on the '''0d_rl_M11_001_L''' and toggle on Editing.

<li>Copy the line from the 2d_po line layer into the 0d_rl line layer.

<li>Turn off editing to save the edits.<br>

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<li>Right click on the '''0d_rl_M11_001_P''' and toggle on Editing.

<li>Turn off editing to save the edits.<br>

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<li>To ensure the point reporting functionality is correct, it needs to be snapped to the start/end of a 1d_nwk line.

<li>Turn off editing to save the edits. <br>

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