| Tool Name | Flow Accumulation (Top-Down) |
| Tool ID | 0 |
| Library ID | ta_hydrology |
| Version | 1.0 |
| Author(s) | O.Conrad (c) 2001-2016, Portions by T.Grabs (c) 2010 |
Bauer, J., Rohdenburg, H. & Bork, H.-R. (1985): Ein Digitales Reliefmodell als Vorraussetzung für ein deterministisches Modell der Wasser- und Stoff-Flüsse. Landschaftsgenese und Landschaftsökologie, 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
| Name | Type | Identifier | Description | Constraints |
|---|---|---|---|---|
| Input | ||||
| Elevation | grid, input | ELEVATION | ||
| Sink Routes | grid, input, optional | SINKROUTE | ||
| Weights | grid, input, optional | WEIGHTS | ||
| Sinks | grid, input, optional | SINKS | A grid indicating sink (terminal) cells. Cells with valid values (i.e. not NoData) act as sinks that capture all incoming flow and sediment and do not route anything downslope. | |
| 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 | ||||
| Step | integer number | 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 Direction [6] Multiple Maximum Downslope Gradient Based Flow Direction 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 number | LINEAR_MIN | flow accumulation threshold (cells) for linear flow routing | Minimum: 0 Default: 500 |
| Convergence | floating point number | CONVERGENCE | Convergence factor for Multiple Flow Direction Algorithm (Freeman 1991). Applies also to the Multiple Triangular Flow Direction 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 |