SAGA-GIS Module Library Documentation (v2.1.3)

Module Flow Path Length

This module 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:

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

- 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

Parameters

 NameTypeIdentifierDescriptionConstraints
InputElevationGrid (input)ELEVATION--
Seeds (*)Grid (optional input)SEED--
OutputFlow Path LengthGrid (output)LENGTH--
OptionsSeeds OnlyBooleanSEEDS_ONLYUse only seed cells as starting points.Default: 0
Flow Routing AlgorithmChoiceMETHOD-Available Choices:
[0] Deterministic 8 (D8)
[1] Multiple Flow Direction (FD8)
Default: 1
Convergence (FD8)Floating pointCONVERGENCEConvergence factor for the 'Multiple Flow Direction' algorithm (after Freeman 1991)Minimum: 0.000000
Default: 1.100000
(*) optional

Command-line

Usage: saga_cmd ta_hydrology 6 -ELEVATION <str> [-SEED <str>] [-LENGTH <str>] [-SEEDS_ONLY <str>] [-METHOD <str>] [-CONVERGENCE <str>]
  -ELEVATION:<str>  	Elevation
	Grid (input)
  -SEED:<str>       	Seeds
	Grid (optional input)
  -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:<str>	Convergence (FD8)
	Floating point
	Minimum: 0.000000
	Default: 1.100000