build_chans: Construct a raster of channel locations from vector or...

Description Usage Arguments Value References Examples

View source: R/build_chans.R

Description

The discretise methods both requires a raster defining the locations of the channel cells and the proportion of each river cell occupied by the channel. A detailed river network (DRN) may be available in vector format and can be used to compute this. If not, the channel location can be inferred from a spatially-distributed metric, typically the topographic wetness index.

Usage

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build_chans(dem, drn, chan.width = 1, atb = NULL, buffer = 10,
  atb.thresh = 0.8, single.chan = TRUE)

Arguments

dem

raster Elevation raster (DEM) using a projected coordinate system (e.g UTM) and regular grid spacing. Not required if atb raster supplied.

drn

SpatialLines Detailed river network (DRN) in vector (ESRI Shapefile) format. Not required if atb raster supplied.

chan.width

numeric Vector of channel widths, in m, for each reach defined in the DRN. Will be recycled if shorter than the number of channels

atb

raster Optional raster used as criteria for locating the channel. Typically the value of the topographic wetness index (TWI) determined from the elevations. Should be in a projected coordinate system (e.g UTM) and use a regular grid spacing.

For the TWI to be meaningful this raster should have a resolution of a least 30m. It can be calculated using the upslope.area method applied to the DEM and atb=TRUE.

buffer

If using a vector input then buffer the DRN by this width to capture all river cells.

atb.thresh

If atb supplied and DRN null then this specifies the threshold value above which cells are identified as containing part of the channel network

single.chan

If using a vector input then the first raster layer returned contains either 1 for a river cell or NA for a non-river cell. Otherwise the values are the line ids of the channel vector, that typically identify individual reaches

Value

A two-band raster with the same dimensions as the elevation or ATB raster whose first layer comprises non-zero cells where identified with the channel and whose second layer holds the proportions of those cells occupied by the channel.

References

Kirkby, M. (1975). Hydrograph modelling strategies. In Peel, R., Chisholm, Michael, Haggett, Peter, & University of Bristol. Department of Geography. (Eds.). Processes in physical and human geography : Bristol essays. pp. 69-90. London: Heinemann Educational.

Examples

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## Not run: 

require(dynatopmodel)
data("brompton")

chan.rast <- build_chans(dem=brompton$dem, drn=brompton$drn, buff=5, chan.width=2)
# show it
sp::plot(chan.rast[[1]], col="green", legend=FALSE)

## End(Not run)

dynatopmodel documentation built on Jan. 20, 2018, 9:02 a.m.