fasterRaster (version 8.4.1.1)

streams,GRaster-method: Create stream network

Description

This function estimates the course of streams and rivers from an elevation raster. It is based on the GRASS tool r.stream.extract, where more details can be found (see grassHelp("r.stream.extract"))

Usage

# S4 method for GRaster
streams(
  x,
  accumulation = NULL,
  depression = NULL,
  flowThreshold = 1,
  dirThreshold = 1,
  montgomery = 0,
  minLength = 1
)

Value

A GRaster.

Arguments

x

A GRaster representing elevation.

accumulation

Either NULL (default) or a raster representing flow accumulation. If not supplied, an accumulation will created internally. You can generate an accumulation raster using flow().

depression

Either NULL (default) or a GRaster representing depressions (areas from which streams will not flow out of).

flowThreshold

Numeric > 0: Minimum threshold for a stream to be generated. The default is 1, which is not necessarily a reasonable value.

dirThreshold

Numeric (default is Inf): When flow exceeds this threshold, its direction is estimated using a single-flow direction algorithm. Below this threshold, a multi-direction flow model is used. This is the d8cut parameter in r.stream.extract, and it is only used if accumulation is NULL. The default is 1, which is not necessarily a reasonable value.

montgomery

Numeric: The "Montgomery" exponent for slope, multiplied by accumulation as per accumulation * slope^montgomery. This value is then compared to the threshold to determine if it is sufficient. The default is 0 (i.e., no slope scaling).

minLength

Numeric: First-order streams less than this length are removed (units in cells). Default is 0 (no removal).

See Also

flow(), flowPath(), GRASS manual for tool r.stream.extract (see grassHelp("r.stream.extract"))

Examples

if (grassStarted()) {

# Setup
library(terra)

# Example data
madElev <- fastData("madElev")

# Convert a SpatRaster to a GRaster
elev <- fast(madElev)

# Calculate stream channels
streams <- streams(elev)
plot(streams)

}