openSTARS (version 1.0.0)

correct_compl_junctions: Correct junctions with three inflows.

Description

At complex junctions (i.e. more than two inflows to an outflow), the outflow is broken into two segments at 1/4 of the DEM's cellsize downstream of the start using v.edit(tool = break). Then, the stream with the smallest angle to the outflow is moved to this new junction using v.edit(tool = vertexmove). So far, this function works only for junctions with three inflows, not more.

Usage

correct_compl_junctions(clean = TRUE, celltoldig = 2)

Arguments

clean

logical; should intermediate files be removed from 'GRASS' session?

celltoldig

integer; number of digits the cell size dimensions are rounded to before it is checked whether they are identical

Value

Nothing. The function changes features in

• 'streams_v': Updated streams with topology (vector)

• 'streams_r': Updated stream raster (new cat) (raster)

and copies the original to

• 'streams_v_o': Originally derived streams with topology (vector)

• 'streams_r_o': Originally derived stream raster (raster).

Examples

# NOT RUN {
# Initiate GRASS session
if(.Platform$OS.type == "windows"){
  gisbase = "c:/Program Files/GRASS GIS 7.2.0"
  } else {
  gisbase = "/usr/lib/grass72/"
  }
initGRASS(gisBase = gisbase,
    home = tempdir(),
    override = TRUE)

# Load files into GRASS
dem_path <- system.file("extdata", "nc", "elev_ned_30m.tif", package = "openSTARS")
sites_path <- system.file("extdata", "nc", "sites_nc.shp", package = "openSTARS")
setup_grass_environment(dem = dem_path, sites = sites_path)
import_data(dem = dem_path, sites = sites_path)
gmeta()

# Derive streams from DEM
derive_streams(burn = 0, accum_threshold = 100, condition = TRUE, clean = TRUE)

# Check and correct complex junctions (there are complex juctions in the 
# example date set if the accumulation threshold is low)
cj <- check_compl_junctions()
if(cj){
  correct_compl_junctions()
}

# plot
dem <- readRAST('dem', ignore.stderr = TRUE)
streams <- readVECT('streams_v', ignore.stderr = TRUE)
streams_orig <- readVECT('streams_v_o', ignore.stderr = TRUE)
# zoom to a relevant part of the dem
plot(dem, col = terrain.colors(20), axes = TRUE, 
  xlim = c(640050,640200), ylim = c(219700,219850))
lines(streams_orig, col = 'red', lwd = 4)
lines(streams, col = 'blue', lty = 2, lwd = 2)
legend("topright", col = c("red", "blue"), lty = c(1,2), lwd = c(4,2), 
  legend = c("original", "corrected"))
# }