Viewing 3D TUFLOW FV Results in QGIS

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Introduction

The QGIS TUFLOW Viewer plugin can be used to display TUFLOW FV results, both as 2D results and 3D results. In order to use the TUFLOW FV plotting tools, the TUFLOW Viewer plugin should be version 3.1.1 or later and the version of QGIS used should be 3.14 or later.

• Open QGIS and open the TUFLOW Viewer plugin.

Opening the Map Output

• Choose File-> Load Results-Map Output and in the resulting dialog, navigate to the Results/ directory and select the PT_000.nc file.

This file contains the 3D results. In the previous sections, we assessed the 3D results using a python library. Further development now means those tools are available with the QGIS interface. The following sections outline the various different options for displaying 3D TUFLOW FV results using the QGIS TUFLOW Viewer plugin.

Time Series Plots

The time-series plots allow the modeller to plot the time varying result output. This can be done for invidiual layers within the 3D water column or it can be depth-averaged over a user-defined set of layers.

• Select the ‘3D to 2D averaging time series’ tool,. Using the drop down menu on the side of the tool icon, select the following:-

• Single Vertical Layer (from top)
• Multi Vertical Layer (from top)

• Set the Single vertical layer (from top) parameters as follows:

This will allow the velocity to be plotted for the layer closest to the surface as well as the 5th layer from the surface.

• Set the Multi vertical layer (from top) parameters as follows:

This will allow us to plot the depth-averaged velocity for the 5 vertical layers closest to the water surface.

The resulting output shows the velocity within the 3D layers within the water column.

• Investigate similar outputs for the particle group 1 concentration. The concentration of particles is reported in mg/l.

You’ll see the bulk of the particles occur in the top most layers with little being mixed within the flow depth.

Note, water depth and water surface elevation do not vary with depth and will therefore cannot be depth-averaged.

Depth-Averaged Cross-Section View

The 3D to 2D averaging cross-section tool allows the modeller to plot the spatial distribution of a results parameter either across a cross section or along a long profile. It allows results output to be plotted for individual 3D layers within the water column or depth-averaged for a number of user-defined layers within the vertical using TUFLOW's depth averaging options.

Note: If you extract a cross section but don't see anything come up in the plot window, please check that you have correctly configured both your QGIS project projection and TUFLOW FV result projection.

• Use the 3D to 2D Averaging Cross-Section tool,, with a similar setup to the above steps to obtain a cross-section of the variation of velocity across a cross-section through the channel width.

This shows the velocity in the top layer and the 5th layer from the top showing how velocity varies within the water column.

• Also, use the tool to take a long section through the reach.

• Right click on the Cross Section/Long Profile window and choose to ‘Clear Plot Window’. This will clear the existing graphs from the plot window.

Curtain Plot

The curtain plot allows a cross-section to be displayed to assess how a particular results parameter varies in both the horizontal and vertical dimensions.

• Use the Curtain plot tool, , to plot a cross-section across the river and assess the horizontal and vertical variation in velocity across the cross-section.

• Within the QGIS TUFLOW Viewer plugin, open the ‘Settings’ menu and select to ‘Show Grid’ and also ‘Mesh intercept locations (for map plotting line types e.g. cross section).

• Click ok.

• Create a new curtain plot across the channel. The QGIS window will now show those mesh elements used to generate the curtain plot.

Vertical Profile Plot

The 3D vertical profile plot allows the viewing of a results parameter through the vertical layers as a function of depth.

• Select the Vertical Profile Plots tool,, and select ‘Velocity’. Click on the mapped results to plot a the velocity profile through the water column.

Summary

The QGIS TUFLOW Viewer plugin provides an excellent tool to assess the 2D and 3D outputs from TUFLOW FV. It allows a number of different approaches to interrogate and analyse the variation in results parameters in both the horizontal and vertical domains. You can return to the particle tracking tutorial here.