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RowCol RF files in TUFLOW GPU, f1 and f2 weighting

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Q:

I have a TUFLOW GPU simulation which I am using “Read RowCol RF == <layer.mid>” to vary my rainfall factors (f1 and f2) on a cell by cell basis.  However, when I review the results it would appear that the multiplication factors are not being used (or used as 1).

 

 

A:

As background for other readers, to gradually vary direct rainfall across your code in both TUFLOW classic and GPU area, you can use the:

Read RowCol RF == <gis_layer>

command and alter the f1 and f2 scaling factors.

The hyetograph weights are multiplied together before being applied to the rainfall.  When running TUFLOW GPU, the GPU module performs a check that these are within a valid range, currently this range is 0 – 1.The range limit is applied in the GPU to limit the amount of memory required and maintain accuracy of resolution. 

If the factors are in the range 0 – 1 they are used as expected.  However, if these are outside the range the following error occurs in the log file:

 

Adding hydrograph weight layer 1 ...

ERROR: Hydrograph weight data not in range [0..1]

 

If the error above is generated, the simulation then discards the weighting factors and proceeds, however, the results should be treated as suspect and not used.  Currently, if this occurs the message is logged to the .gpu.tlf file, however, the simulation is not stopped.  It is likely the for a future release that we will force the simulation to stop.

 

TUFLOW classic allows the these weighting factors to add to more than 1, whereas, the GPU solver is capped as 1.  To maintain consistency with TUFLOW classic, this capped weighting limit is currently under review within the GPU module, we will ensure that should this change then users will be notified.

 

In the interim, to use weighing factors greater than 1 for a TFULOW GPU simulation, you will need to modify the rainfall boundary so that the f1 factors are less than 1.  E.g. multiply the rainfall boundary by 2 and divide the factors by 2 so that they are less than 1. 

 

For future releases, we have been enhancing TUFLOW to support a wider range of rainfall boundaries (e.g. as a series of radar images).  As part of this we are also adding more outputs.  We will be including added the following, to make it easier to track rainfall on a cell by cell basis:

·         Rainfall rate (output as mm/hr)

·         Cumulative rainfall (output as mm)

 

Regards

TUFLOW Support Team

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