TUFLOW NetCDF Raster Output Format

Introduction

This page contains information on the NetCDF file format used for gridded (raster) outputs from a TUFLOW simulation. To specify NetCDF output from TUFLOW the 2016 version or later of TUFLOW must be used and "NC" must be included in the Map Output Data Formats, e.g.
Map Output Format == xmdf nc ! Output both xmdf and NetCDF formats
Additional NetCDF related commands are:
NetCDF Output Compression == {OFF} | ON | compression level <0 – 9>
NetCDF Output Start Date == {2000-01-01 00:00} | OFF | <date in isodate format>
NetCDF Output Time Unit == DAY | {HOUR} | MINUTE
NetCDF Output Direction == {ANGLE} | BEARING
NetCDF Output Format == {Generic} | FEWS
Br> Please refer to the TUFLOW manual for more details on these.

File Format

The output file has been created to work with GIS and the Delft-FEWS software and therefore should be compliant with the NetCDF CF 1.6 conventions. It is noted that the CF 1.6 standard names do not include any allowance for number of the output names such as Hazard and Time of Peak but these are still output.

Global Attributes

There NetCDF has four global attributes:

• Title - The simulation name
• Source - The TUFLOW version which has been used
• References - The documentation of the NetCDF file, i.e. this page!
• Comment - A description of the output.

An example of the Global Attributes is:

Global Attributes:
           title      = 'M01_5m_002_NC2'
           source     = 'TUFLOW Build: 2015-12-BB-Dev-iSP-w64'
           references = 'TUFLOW NetCDF Raster Output Format (http://wiki.tuflow.com/index.php?title=TUFLOW_NetCDF_Raster_Output_Format)'
           comment    = 'Contains raster TUFLOW output, TUFLOW netcdf version: 1'

Dimensions

The output NetCDF will have three or four dimensions depending on if the Generic or FEWS format has been specified. These are:

• x - the number of x coordinates (columns of data)
• y - the number of y coordinates (rows of data)
• time - the number of outputs. Note that this is an unlimited dimension meaning that the number of time changes each time a new output is written
• static_time (FEWS Format only) - This has a value of 1 and is used for storing the time for the static_data (such as maximums)

An example of the Dimensions is:

Dimensions:
           x           = 1946
           y           = 856
           static_time = 1
           time        = 161   (UNLIMITED)

Variables

Both time-varying and ??? variables are output in the same NetCDF file. For example if the model writes depths our every 10 minutes and tracking maximums is enabled (default) then two depth datasets are written: depths and maximum_depths.

Standard Variables

For each simulation the following variables are written:

• x - contains the x coordinates of the output grid
• y - contains the y coordinates of the output grid
• time - contains the times for the temporal outputs
• static time (FEWS only) - contains a single time which is used by FEWS to display the non time varying datasets (such as maximums)

Static Result Variables (single timestep)

There are currently two output formats from TUFLOW, this is controlled with the command:
NetCDF Output Format == {Generic} | FEWS
The file formats are very similar, but for the FEWS format an additional time dimension and time variable "static_time" are used to store a time for the maximum and time of peak data so that it loads into the FEWS interface at an appropriate time.

Generic

This is the default output format and can also be specified by including "NetCDF Output Format == Generic" in the .tcf file.

FEWS

To output in this format users will need to specify "NetCDF Output Format == FEWS" in the .tcf file.