terminal_reaches function

Return terminal reaches from collection intersecting lake

In the case of a network query, a terminal reach is a stream flowline that has no downstream reaches in-network. In the case of a point query, a terminal reach is a flowline that exits the intersecting surface waterbody.

terminal_reaches(
  lon = NA,
  lat = NA,
  buffer_dist = 0.01,
  network = NA,
  lakepoly = NA,
  lakewise = FALSE,
  lakesize_threshold = 4,
  approve_all_dl = FALSE,
  temporary = TRUE,
  ...
)

Arguments

• lon: numeric decimal degree longitude. optional. See Details section.
• lat: numeric decimal degree latitude. optional. See Details section.
• buffer_dist: numeric buffer around lat-lon point in dec. deg.
• network: sf lines collection. optional. See Details section.
• lakepoly: sf polygon. optional. See Details section.
• lakewise: logical. If TRUE, return the terminal reaches of all lakes in the stream network rather than a single terminal reach of the focal lake.
• lakesize_threshold: numeric above which to count as a lake (ha).
• approve_all_dl: logical blanket approval to download all missing data. Defaults to TRUE if session is non-interactive.
• temporary: logical set FALSE to save data to a persistent rappdirs location
• ...: parameters passed on to sf::st_read

Returns

An sf data frame with LINESTRING geometries

Details

There are multiple ways to execute terminal_reaches:

• Only providing lon + lat arguments - this will query the corresponding lake polygon layer and find the terminal reach of the lake intersecting a buffer around the specified point.
• Only providing a lake polygon - this is essentially the same as above except there is no preliminary lake polygon query.
• Only providing a network of stream lines - this provides the most downstream reach irrespective of lakes.

Examples

## Not run:

library(sf)
library(mapview)

coords <- data.frame(lat = 46.32711, lon = -89.58893)
t_reach <- terminal_reaches(coords$lon, coords$lat)

coords <- data.frame(lat = 20.79722, lon = -156.47833)
# use a non-geographic (projected) buffer size
t_reach <- terminal_reaches(coords$lon, coords$lat,
  buffer_dist = units::as_units(5, "km"))

coords  <- data.frame(lat = 42.96628, lon = -89.25264)
t_reach <- terminal_reaches(coords$lon, coords$lat)

coords  <- data.frame(lat = 41.42217, lon = -73.24189)
t_reach <- terminal_reaches(coords$lon, coords$lat)

mapview(st_as_sf(coords, coords = c("lon", "lat"), crs = 4326)) +
  mapview(t_reach$geometry, color = "red")

coords <- data.frame(lat = 41.859080, lon = -71.575422)
network <- nhd_plus_query(lon = coords$lon, lat = coords$lat,
  dsn = "NHDFlowline", buffer_dist = 0.05)$sp$NHDFlowline
t_reach      <- terminal_reaches(network = network)
t_reach_lake <- terminal_reaches(network = network, lakewise = TRUE,
  lakesize_threshold = 1)

mapview(network) + mapview(t_reach_lake, color = "green") +
  mapview(t_reach, color = "red")
## End(Not run)