The slope of the digital elevation model (DEM) is used as friction (cost) surface to compute the cost distance from any grid cell of the raster to the river. A characteristic value (default: the mean) of the cost distance distribution in a region surrounding the river (default: a buffer region of 2 km) is then calculated, and used to threshold the cost-distance surface. The resulting area is then "polygonized" to obtain the valley boundary as a simple feature geometry.
Examples
get_valley(terra::unwrap(bucharest_dem), bucharest_osm$river_centerline)
#> Geometry set for 1 feature
#> Geometry type: MULTIPOLYGON
#> Dimension: XY
#> Bounding box: xmin: 412625.5 ymin: 4914219 xmax: 443449.4 ymax: 4928319
#> Projected CRS: WGS 84 / UTM zone 35N
#> MULTIPOLYGON (((417995.4 4926024, 417995.4 4926...