ISIS 2D Quick Start Guide - Halcrow

ISIS 2D Quick Start Guide
• The seventh column 2D DV/Dt shows the rate of change of volume in the model over
each time step.
• The eighth column 2D V records the total water volume accumulated in the 2D domain.
• The ninth and tenth columns, Trapped (+) and Trapped (-) show the volume loss or
gain due to the dry depth threshold. T
• The last column Q e is the mass balance error, defined as:
The mass balance error indicates the amount of water created (positive value) or lost (negative value)
by the model per second.
It is important that the user checks the mass balance file carefully to ensure the model is behaving
correctly. The total water volume, boundary inflow, and mass balance error are good indication of
whether the model is healthy or not.
After checking mass balance file, the user may want to view the 2D model results and do some postprocessing
of the data. The following list shows the items which modellers normally are interested in
when doing post-processing of the ISIS 2D results data:
• Time series plot for water level and velocity for any active cell in the domain;
• Cross-section plot for water level and velocity, and total water volume pass a
defined cross-section;
• Animation of water levels and velocities for the entire 2D results;
• Maximum flood extent map;
The ways to produce the plots or fulfil the actions mentioned above are described in the sections
below.
2. Viewing a time series plot at a particular point
Time series plot for water levels and velocities at a particular point are important for the modellers in
order to carry on model calibration and validation. There are two ways for creating and viewing time
series of ISIS 2D results:
1. The time series of ISIS 2D results can be viewed using ISIS Mapper;
2. The .CSV file with ISIS 2D results at a user-specified frequency at a particular
point can be created during the ISIS 2D simulation. The parameters for the
output of the results are specified in the ISIS 2D control XML file.
Viewing a time series plots at a particular point using ISIS Mapper
In order to plot the time series of certain variables at a particular point, the user has to load the
model results into ISIS Mapper first. The following four variables can be output: water depth, water
level, flow, and velocity. However, only two variables (one scalar and one vector) can be loaded into
ISIS Mapper at the same time. The example shown on Figure 1 shows a flood map for the same
example model as mentioned in Chapter 2 of this Quick Start Guide. The process of creating such a
flood map is described in Chapter 2 of this Guide (Step "Load the 2D Model Results Data into ISIS
Mapper" of the Sub-Chapter "Viewing the Results Files of the ISIS 2D simulation"). It is recommended
to load an appropriate ground elevation grid in order to overlay the visualised ISIS 2D results with and
to actually see the extents of flooding.
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