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Calculate Geomorphology Metrics from dtm

calc_geomorph_metrics.Rd

This function calculates various geometric and hydrological metrics from a Digital Elevation Model (dtm). It computes terrain attributes, performs hydrological processing (including inverted processing for ridge extraction), and returns all metrics in a structured list.

Usage

calc_geomorph_metrics(
  dtm,
  output_folder = tempdir(),
  contour_interval = 10,
  stream_threshold = 1000,
  breach_dist = 50,
  hillshade_angle = 45,
  hillshade_direction = 270
)

Arguments

dtm

A SpatRaster object imported with terra::rast(). Must be a valid digital elevation model.

output_folder

Character string specifying the directory path for temporary whitebox processing files. Defaults to a temporary directory.

contour_interval

Numeric value for contour line spacing in elevation units. Default is 10.

stream_threshold

Numeric value for stream and ridge extraction threshold (number of cells). Default is 1000. Adjust based on your study area size.

breach_dist

Maximum breach distance for depression filling in cells. Default is 50.

hillshade_angle

Sun angle for hillshade calculation in degrees. Default is 45.

hillshade_direction

Sun direction for hillshade calculation in degrees. Default is 270 (from west).

Value

A list containing the following geometric metrics:

contours

sf object with contour lines

slope

SpatRaster of slope in degrees

aspect

SpatRaster of aspect in radians

hillshade

SpatRaster of hillshade

dtm_filled

SpatRaster of depression-filled dtm

flow_pointer

SpatRaster of D8 flow pointers

flow_acc

SpatRaster of flow accumulation

flow_acc_log

SpatRaster of log-transformed flow accumulation

streams

SpatRaster of extracted stream network

dtm_inverted

SpatRaster of inverted dtm (for ridge analysis)

dtm_filled_inverted

SpatRaster of depression-filled inverted dtm

flow_pointer_inverted

SpatRaster of D8 flow pointers for inverted dtm

flow_acc_inverted

SpatRaster of flow accumulation for inverted dtm

streams_inverted

SpatRaster of extracted streams_inverted

output_folder

Character string of the output folder path used

Details

The function performs the following calculations in order:

  1. Basic terrain attributes (contours, slope, aspect, hillshade)

  2. Depression filling using least-cost breaching

  3. D8 flow pointer calculation

  4. Flow accumulation

  5. Log-transformed flow accumulation

  6. Stream network extraction

  7. Inverted dtm creation (dtm * -1)

  8. Inverted hydrological processing (for ridge extraction)

  9. Ridge network extraction

The inverted hydrological processing creates a "reversed" topography where valleys become ridges and vice versa. This allows for the extraction of ridge networks using the same flow accumulation algorithms used for streams.

Note

Requires the terra, whitebox, and sf packages. Make sure whitebox tools are properly installed with whitebox::install_whitebox().

Examples

if (FALSE) { # \dontrun{

# Load your dtm
dtm <- rast("path/to/your/dtm.tif")

# Calculate all metrics with defaults
metrics <- calc_geomorphology_metrics(dtm)

# Access individual metrics
plot(metrics$slope)
plot(metrics$hillshade)
plot(metrics$streams)
plot(metrics$streams_inverted)

# Custom parameters
metrics <- calc_geomorphology_metrics(
  dtm = dtm,
  output_folder = "C:/my_project/temp",
  contour_interval = 20,
  stream_threshold = 500
)
} # }