# Channel Network

(c) 2001 by O.Conrad
This module derives a channel network based on gridded digital elevation data.
Use the initiation options to determine under which conditions channels shall start.

## Parameters

Grid system
Grid system
  Grid system
Elevation
Input Grid
  A grid that contains elevation data.
Flow Direction
Input Grid
  An optional grid that provides information about flow directions. Values between 1 to 8 force the flow of a cell to be given to one its adjacent neighbor cells (1->NE, 2->E, 3->SE, 4->S, 5->SW, 6->W, 7->NW, 8->N). In case of other values the algorithm will use its own routing scheme. This option is in particular useful to supply the algorithm with routes that lead the flow through closed depression.
Channel Network
Output Grid
  If a cell is part of a channel its value equals the channel order. Otherwise the cell is marked as no-data.
Channel Direction
Output Grid
  If a cell is part of a channel then its value shows the flow direction of the channel (1->NE, 2->E, 3->SE, 4->S, 5->SW, 6->W, 7->NW, 8->N). Otherwise the cell is marked as no-data.
Channel Network
Output Shapes
  This shapes layer will contain the resulting channel network in vector format (lines).
Initiation Grid
Input Grid
  Dependent on the chosen 'Initiation Type' and 'Initiation Threshold' the values of this grid control where a channel is initiated.
Initiation Type
Choice
  Options: - Less than - Equals - Greater than Controls under which condition a channel is initiated.
  Available choices: Less than, Equals, Greater than
Initiation Threshold
Floating point
  Dependent on the chosen 'Initiation Grid' and 'Initiation Type' this value controls under which condition a channel is initiated.
Divergence
Input Grid
  Tracing: Convergence
Tracing: Max. Divergence
Integer
  Tracing: Stop after x cells with divergent flow
  Minimum: 1.0
Tracing: Weight
Input Grid
  Tracing: Weight
Min. Segment Length
Integer
  Minimum Segment Length (Cells)