Given a focal set of FWA watershed groups, return the drainage closure
— every WSG that any focal WSG drains through — ordered downstream-first
by outlet ltree depth (nlevel(outlet) ASC). Pure FWA topology; no
species or bundle knowledge.
Arguments
- conn
A DBI::DBIConnection (e.g. from
frs_db_conn()).- watershed_group_code
Character vector of focal WSG codes (e.g.
c("BULK", "MORR")). Must be non-empty and free ofNA. Codes are upper-cased internally. Focal codes that don't exist intabletrigger a warning and are dropped from the result; if no codes match, the function errors.- table
Character scalar. Fully-qualified table name holding the WSG outlet ltree topology. Default
"public.wsg_outlet".
Value
Character vector of WSG codes — focal plus every WSG they flow through — ordered downstream-first.
Details
Sources the FWA WSG outlet table (default public.wsg_outlet in fwapg).
The closure predicate is f.outlet <@ w.outlet — i.e. every WSG whose
outlet ltree is an ancestor of (or equal to) any focal WSG's outlet.
Order: depth ASC, wsg ASC — so the most downstream WSGs come first and
ties within a depth are alphabetical. Running per-WSG work in this order
persists downstream barriers before upstream WSGs read them, which makes
cross-WSG accessibility flags settle correctly within a single pass.
Examples
if (FALSE) { # \dontrun{
conn <- frs_db_conn()
# Skeena + Peace focal — returns the 15-WSG drainage closure DS-first
frs_wsg_drainage(conn, c("PARS", "BULK"))
#> [1] "KISP" "KLUM" "LKEL" "LSKE" "MSKE" "USKE" "BULK" "FINA"
#> "LBTN" "LPCE" "MORR" "PARA" "PCEA" "UPCE" "PARS"
DBI::dbDisconnect(conn)
} # }