Watershed at Measure

Delineate a watershed polygon at a point on the stream network, defined by blue line key and downstream route measure. Wraps the fwapg fwa_watershedatmeasure() function.

Usage

frs_watershed_at_measure(
  conn,
  blue_line_key,
  downstream_route_measure,
  upstream_measure = NULL,
  upstream_blk = NULL
)

Arguments

conn

A DBI::DBIConnection object (from frs_db_conn()).

blue_line_key

Integer. FWA blue line key identifying the stream.

downstream_route_measure

Numeric. Route measure of the downstream point (metres).

upstream_measure

Numeric or NULL. Route measure of an upstream point. When provided, returns the watershed between the two measures (downstream minus upstream).

upstream_blk

Integer or NULL. Blue line key for the upstream point. Defaults to blue_line_key (same stream). Use when the upstream point is on a tributary.

Value

An sf data frame with a single polygon geometry.

Details

When upstream_measure is provided, returns the difference between the downstream and upstream watersheds — the subbasin between the two points. The upstream point can be on a different blue line key (e.g. a tributary) by specifying upstream_blk.

See also

Other watershed: frs_watershed_split()

Examples

if (FALSE) { # \dontrun{
conn <- frs_db_conn()

# Watershed upstream of a single point
ws <- frs_watershed_at_measure(conn, 360873822, 208877)

# Subbasin between two points on the same stream
aoi <- frs_watershed_at_measure(conn, 360873822, 208877,
  upstream_measure = 233564)

# Subbasin with upstream point on a tributary (different BLK)
aoi <- frs_watershed_at_measure(conn, 360873822, 165115,
  upstream_measure = 838, upstream_blk = 360886221)
DBI::dbDisconnect(conn)
} # }