SAGA-GIS Tool Library Documentation (v9.1.2)

Tool 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.

Flow routing methods provided by this tool:


References


Parameters

 NameTypeIdentifierDescriptionConstraints
InputElevationGrid, inputELEVATION--
Sink Routes (*)Grid, input, optionalSINKROUTE--
Weights (*)Grid, input, optionalWEIGHTS--
Input for Mean over Catchment (*)Grid, input, optionalVAL_INPUT--
Material for Accumulation (*)Grid, input, optionalACCU_MATERIAL--
Accumulation TargetGrid, inputACCU_TARGET--
Linear Flow Threshold Grid (*)Grid, input, optionalLINEAR_VALoptional grid providing values to be compared with linear flow threshold instead of flow accumulation-
Channel Direction (*)Grid, input, optionalLINEAR_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, outputFLOW--
Mean over CatchmentGrid, outputVAL_MEAN--
Accumulated Material (*)Grid, output, optionalACCU_TOTAL--
Accumulated Material (Left Side) (*)Grid, output, optionalACCU_LEFT--
Accumulated Material (Right Side) (*)Grid, output, optionalACCU_RIGHT--
Flow Path Length (*)Grid, output, optionalFLOW_LENGTHaverage distance that a cell's accumulated flow travelled-
Loss through Negative Weights (*)Grid, output, optionalWEIGHT_LOSSwhen using weights without support for negative flow: output of the absolute amount of negative flow that occurred-
OptionsGrid SystemGrid systemPARAMETERS_GRID_SYSTEM--
StepIntegerSTEPFor testing purposes. Only generate flow at cells with step distance (each step row/column).Minimum: 1
Default: 1
Flow Accumulation UnitChoiceFLOW_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 routingMinimum: 0
Default: 500
ConvergenceFloating pointCONVERGENCEConvergence factor for Multiple Flow Direction Algorithm (Freeman 1991). Applies also to the Multiple Triangular Flow Directon Algorithm.Minimum: 0.001000
Default: 1.100000
Contour LengthBooleanMFD_CONTOURInclude (pseudo) contour length as additional weighting factor in multiple flow direction routing, reduces flow to diagonal neighbour cells by a factor of 0.71 (s. Quinn et al. 1991 for details).Default: 0
Prevent Negative Flow AccumulationBooleanNO_NEGATIVESwhen using weights: do not transport negative flow, set it to zero instead; useful e.g. when accumulating measures of water balance.Default: 1
(*) optional

Command-line

Usage: saga_cmd ta_hydrology 0 [-ELEVATION <str>] [-SINKROUTE <str>] [-WEIGHTS <str>] [-FLOW <str>] [-VAL_INPUT <str>] [-VAL_MEAN <str>] [-ACCU_MATERIAL <str>] [-ACCU_TARGET <str>] [-ACCU_TOTAL <str>] [-ACCU_LEFT <str>] [-ACCU_RIGHT <str>] [-STEP <num>] [-FLOW_UNIT <str>] [-FLOW_LENGTH <str>] [-LINEAR_VAL <str>] [-LINEAR_DIR <str>] [-WEIGHT_LOSS <str>] [-METHOD <str>] [-LINEAR_DO <str>] [-LINEAR_MIN <num>] [-CONVERGENCE <double>] [-MFD_CONTOUR <str>] [-NO_NEGATIVES <str>]
  -ELEVATION:<str>     	Elevation
	Grid, input
  -SINKROUTE:<str>     	Sink Routes
	Grid, input, optional
  -WEIGHTS:<str>       	Weights
	Grid, input, optional
  -FLOW:<str>          	Flow Accumulation
	Grid, output
  -VAL_INPUT:<str>     	Input for Mean over Catchment
	Grid, input, optional
  -VAL_MEAN:<str>      	Mean over Catchment
	Grid, output
  -ACCU_MATERIAL:<str> 	Material for Accumulation
	Grid, input, optional
  -ACCU_TARGET:<str>   	Accumulation Target
	Grid, input
  -ACCU_TOTAL:<str>    	Accumulated Material
	Grid, output, optional
  -ACCU_LEFT:<str>     	Accumulated Material (Left Side)
	Grid, output, optional
  -ACCU_RIGHT:<str>    	Accumulated Material (Right Side)
	Grid, output, optional
  -STEP:<num>          	Step
	Integer
	Minimum: 1
	Default: 1
  -FLOW_UNIT:<str>     	Flow Accumulation Unit
	Choice
	Available Choices:
	[0] number of cells
	[1] cell area
	Default: 1
  -FLOW_LENGTH:<str>   	Flow Path Length
	Grid, output, optional
  -LINEAR_VAL:<str>    	Linear Flow Threshold Grid
	Grid, input, optional
  -LINEAR_DIR:<str>    	Channel Direction
	Grid, input, optional
  -WEIGHT_LOSS:<str>   	Loss through Negative Weights
	Grid, output, optional
  -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
	Minimum: 0
	Default: 500
  -CONVERGENCE:<double>	Convergence
	Floating point
	Minimum: 0.001000
	Default: 1.100000
  -MFD_CONTOUR:<str>   	Contour Length
	Boolean
	Default: 0
  -NO_NEGATIVES:<str>  	Prevent Negative Flow Accumulation
	Boolean
	Default: 1