rsaga.topdown.processing {RSAGA}

Top-Down Processing

Description

Calculate the size of the local catchment area (contributing area), accumulated material, and flow path length, using top-down processing algorithms from the highest to the lowest cell.
Top-Down Processing is new with SAGA GIS 2.1.3. See rsaga.parallel.processing() with older versions.

Usage

rsaga.topdown.processing(
  in.dem,
  in.sinkroute,
  in.weight,
  in.mean,
  in.material,
  in.target,
  in.lin.val,
  in.lin.dir,
  out.carea,
  out.mean,
  out.tot.mat,
  out.acc.left,
  out.acc.right,
  out.flowpath,
  step,
  method = "mfd",
  linear.threshold = Inf,
  convergence = 1.1,
  env = rsaga.env(),
  ...
)

Arguments

in.dem

input: digital elevation model (DEM) as SAGA grid file (default file extension: .sgrd)

in.sinkroute

optional input: SAGA grid with sink routes

in.weight

optional input: SAGA grid with weights

in.mean

optional input: SAGA grid for mean over catchment calculation

in.material

optional input: SAGA grid with material

in.target

optional input: SAGA grid of accumulation target

in.lin.val

optional input: SAGA grid providing values to be compared with linear flow threshold instead of catchment area

in.lin.dir

optional input: SAGA grid to be used for linear flow routing, if the value is a valid direction (0-7 = N, NE, E, SE, S, SW, W, NW)

out.carea

output: catchment area grid

out.mean

optional output: mean over catchment grid

out.tot.mat

optional output: total accumulated material grid

out.acc.left

optional output: accumulated material from left side grid

out.acc.right

optional output: accumulated material from right side grid

out.flowpath

optional output: flow path length grid

step

integer >=1: step parameter

method

character or numeric: choice of processing algorithm (default "mfd", or 4):

• 0 Deterministic 8 ("d8" or 0)

• 1 Rho 8 ("rho8", or 1)

• 2 Braunschweiger Reliefmodell ("braunschweig" or 2)

• 3 Deterministic Infinity ("dinf" or 3)

• 4 Multiple Flow Direction ("mfd" or 4)

• 5 Multiple Triangular Flow Direction ("mtfd", or 5)

• 6 Multiple Maximum Gradient Based Flow Direction ("mdg", or 6)

linear.threshold

numeric (number of grid cells): threshold above which linear flow (i.e. the Deterministic 8 algorithm) will be used; linear flow is disabled for linear.threshold=Inf (the default)

convergence

numeric >=0: a parameter for tuning convergent/ divergent flow; default value of 1.1 gives realistic results and should not be changed

env

list, setting up a SAGA geoprocessing environment as created by rsaga.env()

...

further arguments to rsaga.geoprocessor()

Details

Refer to the references for details on the available algorithms.

Value

The type of object returned depends on the intern argument passed to the rsaga.geoprocessor(). For intern=FALSE it is a numerical error code (0: success), or otherwise (the default) a character vector with the module's console output.

Author(s)

Alexander Brenning and Donovan Bangs (R interface), Olaf Conrad (SAGA module), Thomas Grabs (MTFD algorithm)

References

Deterministic 8:

O'Callaghan, J.F., Mark, D.M. (1984): The extraction of drainage networks from digital elevation data. Computer Vision, Graphics and Image Processing, 28: 323-344.

Rho 8:

Fairfield, J., Leymarie, P. (1991): Drainage networks from grid digital elevation models. Water Resources Research, 27: 709-717.

Braunschweiger Reliefmodell:

Bauer, J., Rohdenburg, H., Bork, H.-R. (1985): Ein Digitales Reliefmodell als Vorraussetzung fuer ein deterministisches Modell der Wasser- und Stoff-Fluesse. Landschaftsgenese und Landschaftsoekologie, H. 10, Parameteraufbereitung fuer deterministische Gebiets-Wassermodelle, Grundlagenarbeiten zu Analyse von Agrar-Oekosystemen, eds.: Bork, H.-R., Rohdenburg, H., p. 1-15.

Deterministic Infinity:

Tarboton, D.G. (1997): A new method for the determination of flow directions and upslope areas in grid digital elevation models. Water Ressources Research, 33(2): 309-319.

Multiple Flow Direction:

Freeman, G.T. (1991): Calculating catchment area with divergent flow based on a regular grid. Computers and Geosciences, 17: 413-22.

Quinn, P.F., Beven, K.J., Chevallier, P., Planchon, O. (1991): The prediction of hillslope flow paths for distributed hydrological modelling using digital terrain models. Hydrological Processes, 5: 59-79.

Multiple Triangular Flow Direction:

Seibert, J., McGlynn, B. (2007): A new triangular multiple flow direction algorithm for computing upslope areas from gridded digital elevation models. Water Ressources Research, 43, W04501.

Multiple Flow Direction Based on Maximum Downslope Gradient:

Qin, C.Z., Zhu, A-X., Pei, T., Li, B.L., Scholten, T., Zhou, C.H. (2011): An approach to computing topographic wetness index based on maximum downslope gradient. Precision Agriculture, 12(1): 32-43.

See Also

rsaga.parallel.processing(), rsaga.wetness.index(), rsaga.geoprocessor(), rsaga.env()

Examples

## Not run: 
# Calculation of contributing area with default settings:
rsaga.topdown.processing(in.dem = "dem", out.carea = "carea")
# Calculation of contributing area by maximunm downslope gradient:
rsaga.topdown.processing(in.dem = "dem", out.carea = "carea",
                         method = "mdg")

## End(Not run)