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:
- Deterministic 8 (aka D8, O'Callaghan & Mark 1984)
- Braunschweiger Reliefmodell (Bauer et al. 1985)
- Rho 8 (Fairfield & Leymarie 1991)
- Multiple Flow Direction (Freeman 1991, Quinn et al. 1991)
- Deterministic Infinity (Tarboton 1997)
- Triangular Multiple Flow Direction (Seibert & McGlynn 2007
- Multiple Flow Direction based on Maximum Downslope Gradient (Qin et al. 2011)
References
- 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, p.1-15.
- Fairfield, J. & Leymarie, P. (1991): Drainage networks from grid digital elevation models. Water Resources Research, 27:709-717. doi:10.1029/90WR02658.
- Freeman, G.T. (1991): Calculating catchment area with divergent flow based on a regular grid. Computers and Geosciences, 17:413-22. doi:10.1016/0098-3004(91)90048-I.
- 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. doi:10.1016/S0734-189X(84)80011-0.
- 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. doi:10.1007/s11119-009-9152-y.
- 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. doi:10.1002/hyp.3360050106.
- 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 in SAGA by Thomas Grabs (c) 2007, contact: thomas.grabs@natgeo.su.se, jan.seibert@natgeo.su.se. doi:10.1029/2006WR005128. - 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. doi:10.1029/96WR03137.
- Author: O.Conrad (c) 2001-2016, Portions by T.Grabs (c) 2010
- Menu: Terrain Analysis|Hydrology|Flow Accumulation
Parameters
| | Name | Type | Identifier | Description | Constraints |
|---|
| Input | Elevation | Grid, input | ELEVATION | - | - |
| Sink Routes (*) | Grid, input, optional | SINKROUTE | - | - |
| Weights (*) | Grid, input, optional | WEIGHTS | - | - |
| Input for Mean over Catchment (*) | Grid, input, optional | VAL_INPUT | - | - |
| Material for Accumulation (*) | Grid, input, optional | ACCU_MATERIAL | - | - |
| Accumulation Target | Grid, input | ACCU_TARGET | - | - |
| Linear Flow Threshold Grid (*) | Grid, input, optional | LINEAR_VAL | optional grid providing values to be compared with linear flow threshold instead of flow accumulation | - |
| Channel Direction (*) | Grid, input, optional | LINEAR_DIR | use this for (linear) flow routing, if the value is a valid direction (0-7 = N, NE, E, SE, S, SW, W, NW) | - |
| Output | Flow Accumulation | Grid, output | FLOW | - | - |
| Mean over Catchment | Grid, output | VAL_MEAN | - | - |
| Accumulated Material (*) | Grid, output, optional | ACCU_TOTAL | - | - |
| Accumulated Material (Left Side) (*) | Grid, output, optional | ACCU_LEFT | - | - |
| Accumulated Material (Right Side) (*) | Grid, output, optional | ACCU_RIGHT | - | - |
| Flow Path Length (*) | Grid, output, optional | FLOW_LENGTH | average distance that a cell's accumulated flow travelled | - |
| Loss through Negative Weights (*) | Grid, output, optional | WEIGHT_LOSS | when using weights without support for negative flow: output of the absolute amount of negative flow that occurred | - |
| Options | Grid System | Grid system | PARAMETERS_GRID_SYSTEM | - | - |
| Step | Integer | STEP | For testing purposes. Only generate flow at cells with step distance (each step row/column). | Minimum: 1
Default: 1 |
| Flow Accumulation Unit | Choice | FLOW_UNIT | - | Available Choices:
[0] number of cells
[1] cell area
Default: 1 |
| Method | Choice | METHOD | - | 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 Flow | Boolean | LINEAR_DO | apply linear flow routing (D8) to all cells, having a flow accumulation greater than the specified threshold | Default: 0 |
| Linear Flow Threshold | Integer | LINEAR_MIN | flow accumulation threshold (cells) for linear flow routing | Minimum: 0
Default: 500 |
| Convergence | Floating point | CONVERGENCE | Convergence factor for Multiple Flow Direction Algorithm (Freeman 1991).
Applies also to the Multiple Triangular Flow Directon Algorithm. | Minimum: 0.001000
Default: 1.100000 |
| Contour Length | Boolean | MFD_CONTOUR | Include (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 Accumulation | Boolean | NO_NEGATIVES | when 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