SAGA-GIS Module Library Documentation (v2.2.2)

Module Flow Accumulation (Top-Down)

Top-down processing of cells for calculation of flow accumulation and related parameters. This set of algorithms processes a DEM downwards from the highest to the lowest cell.

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 Resources Research, Vol.33, No.2, p.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

Triangular Multiple Flow Direction
- Seibert, J. / McGlynn, B. (2007):
'A new triangular multiple flow direction algorithm for computing upslope areas from gridded digital elevation models',
Water Resources Research, Vol. 43, W04501
C++ Implementation into SAGA by Thomas Grabs, Copyrights (c) 2007
Contact: thomas.grabs@natgeo.su.se, jan.seibert@natgeo.su.se

Multiple Flow Direction based on Maximum Downslope Gradient:
- Qin, C. Z. / Zhu, A. X. / Pei, T. / Li, B. L. / Scholten, T. / Behrens, T. / & Zhou, C. H. (2011):
'An approach to computing topographic wetness index based on maximum downslope gradient',
Precision Agriculture, 12(1), 32-43.

Parameters

 NameTypeIdentifierDescriptionConstraints
InputElevationGrid (input)ELEVATION--
Sink Routes (*)Grid (optional input)SINKROUTE--
Weight (*)Grid (optional input)WEIGHT--
Input for Mean over Catchment Calculation (*)Grid (optional input)VAL_INPUT--
Material (*)Grid (optional input)MATERIAL--
Accumulation Target (*)Grid (optional input)TARGET--
Linear Flow Threshold Grid (*)Grid (optional input)LINEAR_VALoptional grid providing values to be compared with linear flow threshold instead of flow accumulation-
Channel Direction (*)Grid (optional input)LINEAR_DIRuse this for (linear) flow routing, if the value is a valid direction (0-7 = N, NE, E, SE, S, SW, W, NW)-
OutputFlow AccumulationGrid (output)CAREA--
Mean over CatchmentGrid (output)VAL_MEAN--
Total accumulated Material (*)Grid (optional output)ACCU_TOT--
Accumulated Material from Left Side (*)Grid (optional output)ACCU_LEFT--
Accumulated Material from Right Side (*)Grid (optional output)ACCU_RIGHT--
Flow Path Length (*)Grid (optional output)FLOWLEN--
OptionsStepIntegerSTEP-Minimum: 1
Default: 1
Flow Accumulation UnitChoiceCAREA_UNIT-Available Choices:
[0] number of cells
[1] cell area
Default: 1
MethodChoiceMETHOD-Available Choices:
[0] Deterministic 8
[1] Rho 8
[2] Braunschweiger Reliefmodell
[3] Deterministic Infinity
[4] Multiple Flow Direction
[5] Multiple Triangular Flow Directon
[6] Multiple Maximum Downslope Gradient Based Flow Directon
Default: 4
Thresholded Linear FlowBooleanLINEAR_DOapply linear flow routing (D8) to all cells, having a flow accumulation greater than the specified thresholdDefault: 0
Linear Flow ThresholdIntegerLINEAR_MINflow accumulation threshold (cells) for linear flow routingDefault: 500
ConvergenceFloating pointCONVERGENCEConvergence factor for Multiple Flow Direction Algorithm (Freeman 1991). Applies also to the Multiple Triangular Flow Directon Algorithm.Minimum: 0.000000
Default: 1.100000
Suppress Negative Flow Accumulation ValuesBooleanWEIGHT_GT_0keep accumulated weights above zero; useful e.g. when accumulating measures of water balance.Default: 1
(*) optional

Command-line

Usage: saga_cmd ta_hydrology 0 [-ELEVATION <str>] [-SINKROUTE <str>] [-WEIGHT <str>] [-CAREA <str>] [-VAL_INPUT <str>] [-VAL_MEAN <str>] [-MATERIAL <str>] [-TARGET <str>] [-ACCU_TOT <str>] [-ACCU_LEFT <str>] [-ACCU_RIGHT <str>] [-STEP <num>] [-CAREA_UNIT <str>] [-FLOWLEN <str>] [-LINEAR_VAL <str>] [-LINEAR_DIR <str>] [-METHOD <str>] [-LINEAR_DO <str>] [-LINEAR_MIN <num>] [-CONVERGENCE <str>] [-WEIGHT_GT_0 <str>]
  -ELEVATION:<str>  	Elevation
	Grid (input)
  -SINKROUTE:<str>  	Sink Routes
	Grid (optional input)
  -WEIGHT:<str>     	Weight
	Grid (optional input)
  -CAREA:<str>      	Flow Accumulation
	Grid (output)
  -VAL_INPUT:<str>  	Input for Mean over Catchment Calculation
	Grid (optional input)
  -VAL_MEAN:<str>   	Mean over Catchment
	Grid (output)
  -MATERIAL:<str>   	Material
	Grid (optional input)
  -TARGET:<str>     	Accumulation Target
	Grid (optional input)
  -ACCU_TOT:<str>   	Total accumulated Material
	Grid (optional output)
  -ACCU_LEFT:<str>  	Accumulated Material from Left Side
	Grid (optional output)
  -ACCU_RIGHT:<str> 	Accumulated Material from Right Side
	Grid (optional output)
  -STEP:<num>       	Step
	Integer
	Minimum: 1
	Default: 1
  -CAREA_UNIT:<str> 	Flow Accumulation Unit
	Choice
	Available Choices:
	[0] number of cells
	[1] cell area
	Default: 1
  -FLOWLEN:<str>    	Flow Path Length
	Grid (optional output)
  -LINEAR_VAL:<str> 	Linear Flow Threshold Grid
	Grid (optional input)
  -LINEAR_DIR:<str> 	Channel Direction
	Grid (optional input)
  -METHOD:<str>     	Method
	Choice
	Available Choices:
	[0] Deterministic 8
	[1] Rho 8
	[2] Braunschweiger Reliefmodell
	[3] Deterministic Infinity
	[4] Multiple Flow Direction
	[5] Multiple Triangular Flow Directon
	[6] Multiple Maximum Downslope Gradient Based Flow Directon
	Default: 4
  -LINEAR_DO:<str>  	Thresholded Linear Flow
	Boolean
	Default: 0
  -LINEAR_MIN:<num> 	Linear Flow Threshold
	Integer
	Default: 500
  -CONVERGENCE:<str>	Convergence
	Floating point
	Minimum: 0.000000
	Default: 1.100000
  -WEIGHT_GT_0:<str>	Suppress Negative Flow Accumulation Values
	Boolean
	Default: 1