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.
- Author: O.Conrad (c) 2001-2016, T.Grabs portions (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 | Grid system | - |
| Step | Integer | STEP | - | 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 | 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>] [-METHOD <str>] [-LINEAR_DO <str>] [-LINEAR_MIN <num>] [-CONVERGENCE <double>] [-NO_NEGATIVES <str>] [-WEIGHT_LOSS <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)
-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:<double> Convergence
Floating point
Minimum: 0.000000
Default: 1.100000
-NO_NEGATIVES:<str> Prevent Negative Flow Accumulation
Boolean
Default: 1
-WEIGHT_LOSS:<str> Loss through Negative Weights
Grid (optional output)