# Upslope Area

(c) 2001 by O.Conrad
This module allows you to specify target cells, for which the upslope contributing area shall be identified. The result will give for each cell the percentage of its flow that reaches the target cell(s).
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
Deterministic Infinity:
- Tarboton, D.G. (1997):
'A new method for the determination of flow directions and upslope areas in grid digital elevation models',
Water Ressources 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
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This version uses all valid cells (not 'no data' values) of a given target grid to determine the contributing area. In case no target grid is provided as input, the specified x/y coordinates are used as target point.

## Parameters

Grid system
Grid system
  Grid system
Target Area
Input Grid
Target X coordinate
Floating point
  The x-coordinate of the target point in world coordinates [map units]
Target Y coordinate
Floating point
  The y-coordinate of the target point in world coordinates [map units]
Elevation
Input Grid
Sink Routes
Input Grid
Upslope Area
Output Grid
Method
Choice
  Available choices: Deterministic 8, Deterministic Infinity, Multiple Flow Direction
Convergence
Floating point
  Convergence factor for Multiple Flow Direction algorithm
  Minimum: 0.001