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.
- Freeman, G.T. (1991): Calculating catchment area with divergent flow based on a regular grid. Computers and Geosciences, 17:413-22. ScienceDirect.
- 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. ScienceDirect.
- 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. ResearchGate.
- 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. ResearchGate.
- 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. Wiley. - 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. Wiley.
- 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 (optional input) | SINKROUTE | - | - | |
| Weights (*) | Grid (optional input) | WEIGHTS | - | - | |
| Input for Mean over Catchment (*) | Grid (optional input) | VAL_INPUT | - | - | |
| Material for Accumulation (*) | Grid (optional input) | ACCU_MATERIAL | - | - | |
| Accumulation Target | Grid (input) | ACCU_TARGET | - | - | |
| Linear Flow Threshold Grid (*) | Grid (optional input) | LINEAR_VAL | optional grid providing values to be compared with linear flow threshold instead of flow accumulation | - | |
| Channel Direction (*) | Grid (optional input) | 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 (optional output) | ACCU_TOTAL | - | - | |
| Accumulated Material (Left Side) (*) | Grid (optional output) | ACCU_LEFT | - | - | |
| Accumulated Material (Right Side) (*) | Grid (optional output) | ACCU_RIGHT | - | - | |
| Flow Path Length (*) | Grid (optional output) | FLOW_LENGTH | average distance that a cell's accumulated flow travelled | - | |
| Loss through Negative Weights (*) | Grid (optional output) | 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: 1 | |
| 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: 0.000000 Default: 1.100000 | |
| 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>] [-NO_NEGATIVES <str>] -ELEVATION:<str> Elevation Grid (input) -SINKROUTE:<str> Sink Routes Grid (optional input) -WEIGHTS:<str> Weights Grid (optional input) -FLOW:<str> Flow Accumulation Grid (output) -VAL_INPUT:<str> Input for Mean over Catchment Grid (optional input) -VAL_MEAN:<str> Mean over Catchment Grid (output) -ACCU_MATERIAL:<str> Material for Accumulation Grid (optional input) -ACCU_TARGET:<str> Accumulation Target Grid (input) -ACCU_TOTAL:<str> Accumulated Material Grid (optional output) -ACCU_LEFT:<str> Accumulated Material (Left Side) Grid (optional output) -ACCU_RIGHT:<str> Accumulated Material (Right Side) Grid (optional output) -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 (optional output) -LINEAR_VAL:<str> Linear Flow Threshold Grid Grid (optional input) -LINEAR_DIR:<str> Channel Direction Grid (optional input) -WEIGHT_LOSS:<str> Loss through Negative Weights Grid (optional output) -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: 1 -LINEAR_MIN:<num> Linear Flow Threshold Integer Minimum: 0 Default: 500 -CONVERGENCE:<double> Convergence Floating point Minimum: 0.000000 Default: 1.100000 -NO_NEGATIVES:<str> Prevent Negative Flow Accumulation Boolean Default: 1