derive_flow {rdwplus}

Obtain flow direction and accumulation over a digital elevation model (DEM)

Description

This function computes flow direction and accumulation (among other things) from a DEM. This is done using the r.watershed tool in GRASS.

Usage

derive_flow(
  dem,
  flow_dir,
  flow_acc,
  d8 = TRUE,
  overwrite = FALSE,
  max_memory = 300,
  ...
)

Arguments

dem

A digital elevation model that has been hydrologically corrected.

flow_dir

The name of the output flow direction file in the current GRASS mapset.

flow_acc

The name of the output flow accumulation file in the current GRASS mapset.

d8

A logical indicating whether D8 flow direction should be used. If FALSE, multiple flow direction is allowed. Defaults to TRUE.

overwrite

A logical indicating whether any of the outputs should be allowed to overwrite existing files. Defaults to FALSE.

max_memory

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

...

Additional arguments to r.watershed.

Value

Nothing. Files are written in the current GRASS mapset.

Examples

if(check_running()){
# Load data set
dem <- system.file("extdata", "dem.tif", package = "rdwplus")
stream_shp <- system.file("extdata", "streams.shp", package = "rdwplus")

# Set environment parameters and import data to GRASS
set_envir(dem)
vector_to_mapset(vectors = c(stream_shp))

# Create binary stream
out_name <- paste0(tempdir(), "/streams_rast.tif")
rasterise_stream("streams", out_name, 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 =  "dem_fill.tif", out_fd = "fd1.tif", overwrite = TRUE)

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

# Plot
plot_GRASS("fdir.tif", col = topo.colors(6))
plot_GRASS("facc.tif", col = topo.colors(6))
}