rdwplus (version 0.1.0)

get_flow_length: Derive a flow length to streams and outlets

Description

Given a (hydrologically corrected, see fill_sinks) DEM, this function produces a flow accumulation grid which shows the upstream area that flows into each cell in the DEM. Note that this function calls r.stream.distance, which is a GRASS GIS add-on. It can be installed through the GRASS GUI.

Usage

get_flow_length(
  str_rast,
  flow_dir,
  out,
  to_outlet = FALSE,
  overwrite = FALSE,
  max_memory = 300
)

Value

Nothing. A file with the name out will be written to GRASS's current workspace.

Arguments

str_rast

Rasterized unary streams file.

flow_dir

Flow direction raster.

out

A file name for the output raster of flow lengths.

to_outlet

Calculate parameters for outlets flag. Defaults to FALSE for streams.

overwrite

Overwrite flag. Defaults to FALSE.

max_memory

Max memory used in memory swap mode (MB). Defaults to 300.

Examples

# Will only run if GRASS is running
if(check_running()){
# Load data set
dem <- system.file("extdata", "dem.tif", package = "rdwplus")
sites <- system.file("extdata", "site.shp", package = "rdwplus")
stream_shp <- system.file("extdata", "streams.shp", package = "rdwplus")

# Set environment parameters and import data to GRASS
set_envir(dem)
raster_to_mapset(rasters = dem, as_integer = FALSE)
vector_to_mapset(vectors = c(sites, stream_shp))

# Create binary stream
rasterise_stream("streams", "streams_rast.tif", overwrite = TRUE)
reclassify_streams("streams_rast.tif", "streams_binary.tif", 
out_type = "binary", overwrite = TRUE)

# Burn dem 
burn_in(dem = "dem.tif", stream = "streams_binary.tif",
 out = "dem_burn.tif", burn = 10, overwrite = TRUE)

# Fill sinks
fill_sinks(dem = "dem_burn.tif", out = "dem_fill.tif", size = 1, overwrite = TRUE)

# Derive flow accumulation and direction grids
derive_flow(dem = "dem_fill.tif", flow_dir = "fdir.tif",
 flow_acc = "facc.tif", overwrite = TRUE)

# Snap sites to pour points (based on flow accumulation)
snap_sites(sites = "site", flow_acc = "facc.tif", max_move = 2, 
out = "snapsite.shp", overwrite = TRUE)

# Get pour points / outlets as raster cells 
rowID <- 1
site_coords <- readVECT("site")
coords_i <- site_coords@coords[rowID, 1:2]
coords_i_out <- paste0("pour_point_", rowID)
coord_to_raster(coords_i, coords_i_out, TRUE)

# Name for flow length raster
current_flow_out <- paste0("flowlenOut_", rowID, ".tif")

# Create it
get_flow_length(str_rast = coords_i_out, 
flow_dir = "fdir.tif", 
out = current_flow_out, 
to_outlet = TRUE, 
overwrite = TRUE)

# Plot 
plot_GRASS(current_flow_out, col = topo.colors(15))
}