For a more detailed analysis of an urban river corridor, corridor-level delineation may not be sufficient. The corridor needs to be subdivided into smaller morphological units. Segmentation is a process of subdividing the corridor by using major transversal road or rail infrastructure lines.
By default, the all-in-one function delineate_corridor()
only returns the corridor boundary. The corridor can be segmented either
by setting the argument segments = TRUE in
delineate_corridor() or by using the
get_segments() function in a separate step.
To demonstrate this as a separate step, we will use the
bucharest_osm$corridor, bucharest_osm$streets
and bucharest_osm$railways layers from the package data as
input.
We first prepare the network and select all the streets and railways
that cover the river corridor plus a small buffer region (see also
vignette("network-preparation")):
# TODO remove eval=FALSE when the corridor is available as packaged data
# Build combined street and railway network
network <- bind_rows(bucharest_osm$streets, bucharest_orsm$railways) |>
as_sfnetwork(directed = FALSE)
# Add a 100 meter buffer region to the corridor
corridor_buffer <- sf::st_buffer(bucharest_osm$corridor, 100)
# Filter the network to the area of interest
network_filtered <- filter_network(network, corridor_buffer)We then delineate segments in the corridor. The algorithm spits the corridor using river-crossing transversal edges that form continuous lines in the network:
# TODO remove eval=FALSE when the corridor is available as packaged data
segmented_corridor <- get_segments(bucharest_delineation$corridor,
network_filtered)