Tool Flow Path Length

This tool calculates the average flow path length starting from the seeds, that are given by the optional 'Seeds' grid and optionally from cells without upslope contributing areas (i.e. summits, ridges). Seeds will be all grid cells, that are not 'no data' values. If seeds are not given, only summits and ridges as given by the flow routing will be taken into account. Available flow routing methods are based on the 'Deterministic 8 (D8)' (Callaghan and Mark 1984) and the 'Multiple Flow Direction (FD8)' (Freeman 1991, Quinn et al. 1991) algorithms.

References

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.
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.

Author: O.Conrad (c) 2005
Menu: Terrain Analysis|Hydrology|Flow Accumulation

Parameters

	Name	Type	Identifier	Description	Constraints
Input	Elevation	Grid, input	`ELEVATION`	-	-
Input	Seeds (*)	Grid, input, optional	`SEED`	-	-
Output	Flow Path Length	Grid, output	`LENGTH`	-	-
Options	Grid System	Grid system	`PARAMETERS_GRID_SYSTEM`	-	-
	Seeds Only	Boolean	`SEEDS_ONLY`	Use only seed cells as starting points.	Default: 0
	Flow Routing Algorithm	Choice	`METHOD`	-	Available Choices: [0] Deterministic 8 (D8) [1] Multiple Flow Direction (FD8) Default: 1
	Convergence (FD8)	Floating point	`CONVERGENCE`	Convergence factor for the 'Multiple Flow Direction' algorithm (after Freeman 1991)	Minimum: 0.001000 Default: 1.100000
(*) optional

Command-line

Usage: saga_cmd ta_hydrology 6 [-ELEVATION <str>] [-SEED <str>] [-LENGTH <str>] [-SEEDS_ONLY <str>] [-METHOD <str>] [-CONVERGENCE <double>]
  -ELEVATION:<str>     	Elevation
	Grid, input
  -SEED:<str>          	Seeds
	Grid, input, optional
  -LENGTH:<str>        	Flow Path Length
	Grid, output
  -SEEDS_ONLY:<str>    	Seeds Only
	Boolean
	Default: 0
  -METHOD:<str>        	Flow Routing Algorithm
	Choice
	Available Choices:
	[0] Deterministic 8 (D8)
	[1] Multiple Flow Direction (FD8)
	Default: 1
  -CONVERGENCE:<double>	Convergence (FD8)
	Floating point
	Minimum: 0.001000
	Default: 1.100000