Skip to contents

Flag whether each flowline is a direct constituent of its flowpath's line

Source: R/flag_flowpath_constituents.R
flag_flowpath_constituents.Rd

Adds a logical flowpath_constituent attribute to the flowlines layer. A flowline is a constituent (TRUE) when its geometry lies on the line that its aggregate flowpath traces from outlet to head: i.e. it is directly part of flowpath_id. Member flowlines that enter the flowpath as tributaries (a branch that drains into the stem but whose channel the flowpath line does not trace) are FALSE.

The test is geometric and matches the flowpath line by construction: extend_flowpaths_to_mainstem() builds each flowpath line by merging its stem member reaches, so a constituent's geometry is a sub-segment of the line (coverage ~1) while a tributary branches away (coverage low). A flowline is a constituent when at least cov_threshold of its length lies within tol_m of its flowpath's line. Every flowpath is guaranteed at least one constituent: if no member clears the threshold (a flowpath still carrying the aggregated original, non-member line), its single best-covered member is flagged.

Usage

flag_flowpath_constituents(
  input_gpkg,
  flowpath_layer = "flowpaths",
  flowlines_layer = "flowlines",
  tol_m = 5,
  cov_threshold = 0.5
)

Arguments

input_gpkg

Path to a GeoPackage containing flowpath_layer and flowlines_layer.

flowpath_layer, flowlines_layer

Layer names. Defaults "flowpaths" / "flowlines".

tol_m

Buffer (m) around the flowpath line within which a flowline segment counts as "on the line". Default 5.

cov_threshold

Fraction of a flowline's length that must lie on the line for it to be a constituent. Default 0.5.

Value

Invisibly, the number of constituent flowlines. Adds flowpath_constituent (logical) to flowlines_layer, overwriting it in place.

Routing contract

OWP routes on the flowlines coincident with flowpaths (flowpath_constituent == TRUE), that subset IS the routing network, not a descriptive overlay. It must be closed under flowline_toid: a coincident flowline's downstream must resolve to another coincident flowline. Do not fix a routing gap by filtering the mask; dropping a non-coincident connector reach that carries a coincident reach's downstream link would leave the routing set disconnected. A coincident flowline whose flowline_toid points to a non-coincident reach is a routing-set gap (detected by the coincident_flowline_toid_closed invariant); the remedy is to re-point the routing toid across the intervening non-coincident reaches to the next coincident flowline. flowpath_constituent == FALSE reaches are off-network tributary / connector geometry; a flowline's flowline_toid may legitimately name a reach in a different flowpath (a tributary confluence).

Examples

if (FALSE) { # \dontrun{
flag_flowpath_constituents("ngen_vpu01.gpkg")
} # }