Package 'sealeveltools'

Adjust terrain elevations relative to sea-level change

Description

'adjustSeaLevel()' recalculates terrain elevations relative to a modified sea-level datum. The function simulates sea-level rise or fall by shifting elevation values accordingly.

If bathymetric data is provided, submerged terrain is merged with the DTM to produce a continuous DEM. This is particularly useful for: coastal engineering studies, paleogeographic reconstructions, archaeological landscape exposure modelling and climate change impact assessments.

Optional gap-filling enables reconstruction of missing terrain areas through iterative focal interpolation.

Usage

adjustSeaLevel(
  dtm,
  seaLevelChange,
  bathymetry = NULL,
  studyArea = NULL,
  fillGaps = FALSE,
  removeUnder = NULL,
  plot = FALSE,
  filename = "",
  overwrite = FALSE,
  wopt = list()
)

Arguments

dtm	'SpatRaster': Digital Terrain Model.
seaLevelChange	'numeric': Sea level change value. Positive = sea level rise. Negative = sea level drop.
bathymetry	'SpatRaster' (optional): Bathymetric raster to merge with DTM.
studyArea	'SpatVector' (optional): Study area polygon to which to crop results.
fillGaps	'logical' (default 'FALSE'): Whether to iteratively fill NA gaps.
removeUnder	'numeric' (optional): If specified, removes all elevations under defined threshold.
plot	'logical' (default 'FALSE'): Whether to visualize results
filename	'character' (optional): Output file name, skipped if left empty
overwrite	'logical' (default 'FALSE'): If 'TRUE', 'filename' is overwritten
wopt	'list()': list with named options for writing files as in 'writeRaster'

Value

'SpatRaster': DEM adjusted for sea level change.

Examples

library(terra)

### Create dummy DTM and Bathymetric data ###
nr <- 300
nc <- 300
lon <- seq(-10, 10, length.out = nc)
lat <- seq(-10, 10, length.out = nr)

data_mat <- matrix(NA, nrow = nr, ncol = nc)
for (i in 1:nr) {
  for (j in 1:nc) {
    terrain <- 500 * exp(-(lon[j]^2 + lat[i]^2) / 10)
    data_mat[i, j] <- -1000 + 1000 * exp(-(lon[j]^2 + lat[i]^2) / 50) + terrain + rnorm(1, 0, 5)
  }
}

### Create SpatRast data ###
rast_demo <- rast(ncols = 300, nrows = 300, xmin = 0, xmax = 300, ymin = 0, ymax = 300)
values(rast_demo) <- data_mat

dtm_demo <- rast_demo
dtm_demo[dtm_demo[] <= 0] <- NA
# plot(dtm_demo)

bathy_demo <- rast_demo
bathy_demo[bathy_demo[] > 0] <- NA
# plot(bathy_demo)

### Rise sea level ###
dtm_rise <- adjustSeaLevel(dtm = dtm_demo, seaLevelChange = 100, plot = TRUE)

### Lower sea level with bathymetric data ###
dtm_lower <- adjustSeaLevel(
  dtm = dtm_demo, seaLevelChange = -100,
  bathy = bathy_demo, plot = TRUE
)

### Lower sea level with bathymetric data and remove areas under -500 ###
dtm_lower <- adjustSeaLevel(
  dtm = dtm_demo, seaLevelChange = -100,
  bathy = bathy_demo, removeUnder = -500, plot = TRUE
)

### Lower sea level with bathymetric data and gap-filling ###
dtm_demo[dtm_demo[] <= 3] <- NA # introduce missing data
dtm_lower_gaps <- adjustSeaLevel(
  dtm = dtm_demo, seaLevelChange = -50,
  bathy = bathy_demo, plot = TRUE
)
dtm_lower_filled <- adjustSeaLevel(
  dtm = dtm_demo, seaLevelChange = -50,
  bathy = bathy_demo, fillGaps = TRUE, plot = TRUE
)

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