QGIS algorithm - r.watershed

Source: R/grass_r_watershed.R

QGIS Algorithm provided by GRASS r.watershed (grass:r.watershed). Watershed basin analysis program.

grass_r_watershed(
  elevation = qgisprocess:::qgis_default_value(),
  depression = qgisprocess:::qgis_default_value(),
  flow = qgisprocess:::qgis_default_value(),
  disturbed_land = qgisprocess:::qgis_default_value(),
  blocking = qgisprocess:::qgis_default_value(),
  threshold = qgisprocess:::qgis_default_value(),
  max_slope_length = qgisprocess:::qgis_default_value(),
  convergence = qgisprocess:::qgis_default_value(),
  memory = qgisprocess:::qgis_default_value(),
  .s = qgisprocess:::qgis_default_value(),
  .m = qgisprocess:::qgis_default_value(),
  .arg_4 = qgisprocess:::qgis_default_value(),
  .a = qgisprocess:::qgis_default_value(),
  .b = qgisprocess:::qgis_default_value(),
  accumulation = qgisprocess:::qgis_default_value(),
  drainage = qgisprocess:::qgis_default_value(),
  basin = qgisprocess:::qgis_default_value(),
  stream = qgisprocess:::qgis_default_value(),
  half_basin = qgisprocess:::qgis_default_value(),
  length_slope = qgisprocess:::qgis_default_value(),
  slope_steepness = qgisprocess:::qgis_default_value(),
  tci = qgisprocess:::qgis_default_value(),
  spi = qgisprocess:::qgis_default_value(),
  GRASS_REGION_PARAMETER = qgisprocess:::qgis_default_value(),
  GRASS_REGION_CELLSIZE_PARAMETER = qgisprocess:::qgis_default_value(),
  GRASS_RASTER_FORMAT_OPT = qgisprocess:::qgis_default_value(),
  GRASS_RASTER_FORMAT_META = qgisprocess:::qgis_default_value(),
  ...,
  .complete_output = .complete_output_option(),
  .quiet = .quiet_option(),
  .messages = .message_option()
)

Arguments

elevation

raster - Elevation. Path to a raster layer.

depression

raster - Locations of real depressions. Path to a raster layer.

flow

raster - Amount of overland flow per cell. Path to a raster layer.

disturbed_land

raster - Percent of disturbed land, for USLE. Path to a raster layer.

blocking

raster - Terrain blocking overland surface flow, for USLE. Path to a raster layer.

threshold

number - Minimum size of exterior watershed basin. A numeric value. field:FIELD_NAME to use a data defined value taken from the FIELD_NAME field. expression:SOME EXPRESSION to use a data defined value calculated using a custom QGIS expression.

max_slope_length

number - Maximum length of surface flow, for USLE. A numeric value. field:FIELD_NAME to use a data defined value taken from the FIELD_NAME field. expression:SOME EXPRESSION to use a data defined value calculated using a custom QGIS expression.

convergence

number - Convergence factor for MFD (1-10). A numeric value. field:FIELD_NAME to use a data defined value taken from the FIELD_NAME field. expression:SOME EXPRESSION to use a data defined value calculated using a custom QGIS expression.

memory

number - Maximum memory to be used with -m flag (in MB). A numeric value. field:FIELD_NAME to use a data defined value taken from the FIELD_NAME field. expression:SOME EXPRESSION to use a data defined value calculated using a custom QGIS expression.

.s

boolean - Enable Single Flow Direction (D8) flow (default is Multiple Flow Direction). 1 for true/yes. 0 for false/no. field:FIELD_NAME to use a data defined value taken from the FIELD_NAME field. expression:SOME EXPRESSION to use a data defined value calculated using a custom QGIS expression. Original algorithm parameter name: -s.

.m

boolean - Enable disk swap memory option (-m): Operation is slow. 1 for true/yes. 0 for false/no. field:FIELD_NAME to use a data defined value taken from the FIELD_NAME field. expression:SOME EXPRESSION to use a data defined value calculated using a custom QGIS expression. Original algorithm parameter name: -m.

.arg_4

boolean - Allow only horizontal and vertical flow of water. 1 for true/yes. 0 for false/no. field:FIELD_NAME to use a data defined value taken from the FIELD_NAME field. expression:SOME EXPRESSION to use a data defined value calculated using a custom QGIS expression. Original algorithm parameter name: -4.

.a

boolean - Use positive flow accumulation even for likely underestimates. 1 for true/yes. 0 for false/no. field:FIELD_NAME to use a data defined value taken from the FIELD_NAME field. expression:SOME EXPRESSION to use a data defined value calculated using a custom QGIS expression. Original algorithm parameter name: -a.

.b

boolean - Beautify flat areas. 1 for true/yes. 0 for false/no. field:FIELD_NAME to use a data defined value taken from the FIELD_NAME field. expression:SOME EXPRESSION to use a data defined value calculated using a custom QGIS expression. Original algorithm parameter name: -b.

accumulation

rasterDestination - Number of cells that drain through each cell. Path for new raster layer.

drainage

rasterDestination - Drainage direction. Path for new raster layer.

basin

rasterDestination - Unique label for each watershed basin. Path for new raster layer.

stream

rasterDestination - Stream segments. Path for new raster layer.

half_basin

rasterDestination - Half-basins. Path for new raster layer.

length_slope

rasterDestination - Slope length and steepness (LS) factor for USLE. Path for new raster layer.

slope_steepness

rasterDestination - Slope steepness (S) factor for USLE. Path for new raster layer.

tci

rasterDestination - Topographic index ln(a / tan(b)). Path for new raster layer.

spi

rasterDestination - Stream power index a * tan(b). Path for new raster layer.

GRASS_REGION_PARAMETER

extent - GRASS GIS 7 region extent. A comma delimited string of x min, x max, y min, y max. E.g. '4,10,101,105'. Path to a layer. The extent of the layer is used..

GRASS_REGION_CELLSIZE_PARAMETER

number - GRASS GIS 7 region cellsize (leave 0 for default). A numeric value. field:FIELD_NAME to use a data defined value taken from the FIELD_NAME field. expression:SOME EXPRESSION to use a data defined value calculated using a custom QGIS expression.

GRASS_RASTER_FORMAT_OPT

string - Output Rasters format options (createopt). String value. field:FIELD_NAME to use a data defined value taken from the FIELD_NAME field. expression:SOME EXPRESSION to use a data defined value calculated using a custom QGIS expression.

GRASS_RASTER_FORMAT_META

string - Output Rasters format metadata options (metaopt). String value. field:FIELD_NAME to use a data defined value taken from the FIELD_NAME field. expression:SOME EXPRESSION to use a data defined value calculated using a custom QGIS expression.

...

further parameters passed to qgisprocess::qgis_run_algorithm()

.complete_output

logical specifying if complete out of qgisprocess::qgis_run_algorithm() should be used (TRUE) or first output (most likely the main) should read (FALSE). Default value is TRUE.

.quiet

logical specifying if parameter .quiet for qgisprocess::qgis_run_algorithm() Default value is TRUE.

.messages

logical specifying if messages from qgisprocess::qgis_run_algorithm() should be printed (TRUE) or not (FALSE). Default value is FALSE.

Details

Outputs description

  • accumulation - outputRaster - Number of cells that drain through each cell

  • basin - outputRaster - Unique label for each watershed basin

  • drainage - outputRaster - Drainage direction

  • half_basin - outputRaster - Half-basins

  • length_slope - outputRaster - Slope length and steepness (LS) factor for USLE

  • slope_steepness - outputRaster - Slope steepness (S) factor for USLE

  • spi - outputRaster - Stream power index a * tan(b)

  • stream - outputRaster - Stream segments

  • tci - outputRaster - Topographic index ln(a / tan(b))