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NAME
r.stream.channel - Calculates local parameters for individual streams.
KEYWORDS
raster,
hydrology,
stream network
SYNOPSIS
r.stream.channel
r.stream.channel --help
r.stream.channel [-dlcm] stream_rast=name direction=name elevation=name [identifier=name] [distance=name] [difference=name] [gradient=name] [curvature=name] [memory=integer] [--overwrite] [--help] [--verbose] [--quiet] [--ui]
Flags:
- -d
- Calculate parameters from outlet (downstream values)
- -l
- Calculate local values (for current cell)
- -c
- Calculate distance in cell count (ignored local)
- -m
- Use memory swap (operation is slow)
- --overwrite
- Allow output files to overwrite existing files
- --help
- Print usage summary
- --verbose
- Verbose module output
- --quiet
- Quiet module output
- --ui
- Force launching GUI dialog
Parameters:
- stream_rast=name [required]
- Name of input raster map with stream network
- direction=name [required]
- Name of input raster map with flow direction
- elevation=name [required]
- Name of input elevation raster map
- identifier=name
- Name for output unique stream identifier raster map
- distance=name
- Name for output init/join/outlet distance raster map
- difference=name
- Name for output elevation init/join/outlet difference raster map
- gradient=name
- Name for output mean init/join/outlet gradient of stream raster map
- curvature=name
- Name for output local stream curvature raster map
- memory=integer
- Maximum memory used in memory swap mode (MB)
- Default: 300
The module
r.stream.channel is prepared to calculate some local properties
of the stream network. It is supplementary module for
r.stream.order, and
r.stream.distance to investigate channel subsystem. For slope subsystem
parameters is
r.stream.slope. It may use ordered or unordered network. It
calculate parameters for every segment between it init to outlet/join to the
next stream. it also may calculate parameters between outlet and segment's init.
It can calculate parameters for every orders but best results are for these
orders where order remains unchanged from stream init to natural outlet (Hack
and Horton ordering).
- -d
- Calculate downstream distance (from current cell DOWNSTREAM to outlet/join).
Default is upstream (from current cell upstream to init/join.
- -m
- Only for very large data sets. Uses segment library to optimize memory
consumption during analysis
- stream_rast
- Stream network: name of input stream map. Map may be ordered according to one
of the r.stream.order ordering systems as well as unordered (with original stream
identifiers). Because the streams network produced by r.watershed and
r.stream.extract may slightly differ in detail it is required to use both stream
and direction map produced by the same module. Non-stream cell values must be
set to NULL.
- direction
- Flow direction: name of input direction map produced by
r.watershed or r.stream.extract. If the r.stream.extract
output map is used, it contains non-NULL values only in places where streams are
present. NULL cells are ignored; zero and negative values are valid direction data
if they vary from -8 to 8 (CCW from East in steps of 45 degrees). The direction
map shall be of integer type (CELL). The region resolution and map resolution
must be the same. Also the stream_rast network map must have the same
resolution. If resolutions differ the module informs about it and stops. Region
boundary and maps boundary may be different but it may lead to unexpected
results.
- elevation
- Elevation: name of input elevation map. Map can be of type CELL, FCELL or
DCELL. It is not restricted to resolution of region settings as streams and
direction.
- distance
- Upstream distance of current cell to the init/join. Flag modifications:
-d: downstream distance of current cell to the join/outlet;
-l: local distance between current cell and next cell. In most cases cell
resolution and sqrt2 of cell resolution. useful when projection is LL or NS and
WE resolutions differs. Flag -d ignored
-c: distance in cells. Map is written as double. Use r.mapcalc to convert
to integer. Flags -l and -d ignored.
- difference
- Upstream elevation difference between current cell to the init/join. It we
need to calculate parameters different than elevation. If we need to calculate
different parameters than elevation along streams (for example precipitation or
so) use necessary map as elevation. Flag modifications:
-d: downstream difference of current cell to the join/outlet;
-l: local difference between current cell and next cell. With flag
calculates difference between previous cell and current cell
-c: Ignored.
- gradient
- Upstream mean gradient between current cell and the init/join. Flag
modifications:
-d: downstream mean gradient between current cell and the
join/outlet;
-l: local gradient between current cell and next cell. Flag -d ignored
-c: Ignored.
- curvature
- Local stream course curvature of current cell. Calculated according
formula: first_derivative/(1-second_derivative2)3/2
Flag modifications:
-d: ignored;
-l: Ignored.
-c: Ignored.
- identifier
- Integer map: In ordered stream network there are more than one segment
(segment: a part of the network where order remains unchanged) with the same
order. To identify particular segments (for further analysis) every segment
receive his unique identifier.
This example shows how to visualise the change of gradient map along the main
stream of the catchment:
g.region -p -a raster=elevation
r.watershed elevation=elevation threshold=10000 drainage=direction stream=streams
r.stream.order streams=streams direction=direction hack=hack
r.stream.channel streams=hack direction=direction elevation=elevation \
identifier=stream_identifier distance=stream_distance gradient=stream_gradient
# Eg., 495 is a stream identifier. May be different in different situation
r.mapcalc "stgrad = if(stream_identifier==495,float(stream_gradient),null())"
r.mapcalc "stdist = if(stream_identifier==495,float(stream_distance),null())"
# Use R for plotting
R
library(spgrass6)
r=readRAST6(c("stdist","stgrad"),NODATA=-9999)
p=subset(r@data,!is.na(r@data$dist))
sorted=p[order(p$stdist),]
plot(sorted,stdist~stgrad,type="l")
r.mapcalc,
r.stream.distance,
r.stream.extract,
r.stream.order,
r.stream.basins,
r.stream.segment,
r.stream.slope,
r.stream.snap,
r.stream.stats,
r.watershed
Jarek Jasiewicz, Adam Mickiewicz University, Geoecology and Geoinformation
Institute.
Last changed: $Date: 2014-12-27 14:30:46 +0100 (Sat, 27 Dec 2014) $
SOURCE CODE
Available at: r.stream.channel source code (history)
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GRASS Development Team,
GRASS GIS 7.4.5svn Reference Manual