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FAQ/ When the inundation depth is output to the GIS, the inundation area may be displayed as an enclave.

If you export the simulation results in MILIT CSV format and display them in the GIS, the flooding will be sparsely flying.

What is the cause? Is there a solution?

This behavior occurred in certain situations. The procedure is as follows.

  • In DioVISTA, the target area was continuously flooded.
  • The results were exported in MLIT CSV format and stored in a folder called BP001.
  • Of the exported files, BP001_TIME. All cells in CSV are visualized in GIS.
  • The mesh along the river is not displayed in the GIS. These cells seemingly have a very shallow flood depth.

response

There are two countermeasures. Please choose whichever is most convenient for you.

  • Fix 1: Change the Calculation Method
  • Fix 2: Change the Calculation Results Conversion Method

Measure 1 changes the calculation method. Therefore, you must redo the simulation calculations. For details, please refer to FAQ/Specifying the effective minimum value of inundation depth.

Countermeasure 2 is explained here. In Fix 2, change the conversion method when converting the calculation results to CSV. Therefore, there is no need to redo the simulation calculations.

Action: Change the method of converting calculation results

Specify option -z in dfsConv64.exe.

dfsConv64.exe use options -z and options -R .

If the option is -z specified, the immersion depth is output greater than 0 m. If no option is specified, the output is a depth of 0.005 m or greater.

When Optional -R is specified, variables such as immersion depth are output rounded to three decimal places.

For more information, see Technical Reference Batch Processing / MLIT CSV Conversion.

cause

The reason why inundation areas appear as enclaves in GIS is that cells with a depth of less than 0.005 m in DioVISTA are not output to MLIT CSV format.

The cause of this phenomenon lies in the handling of immersion depths of less than 1 cm. The MLIT CSV format specifies that the inundation depth should be output with two decimal places. Therefore, the MLIT CSV format requires care when handling immersion depths of less than 1 cm.

When outputting from DioVISTA to MLIT CSV format, the following behavior is performed by default.

  • Cells with a depth of 0.005 m or more in DioVISTA will be output as 0.01 in MLIT format.
  • Cells with a water depth of less than 0.005 m in DioVISTA will not be output to the MLIT format.

The option -z changes the behavior to the following:

  • Cells with a depth of 0.005 m or more in DioVISTA will be output as 0.01 in MLIT format.
  • Cells with a water depth of less than 0.005 m in DioVISTA will be output as 0.00 in MLIT format.

For more information about the logic, see Batch Processing/MLIT NetCDF Conversion to Format/Options -z -R .

Last update: 2023-03-17