The goal of this vignette is to demonstrate how to pull the stream network associated with a waterbody catchment. We will use the
extract_network function to accomplish this task using the built-in
library(nhdR) library(dplyr) library(ggplot2) library(sf)
Let’s start by pulling the coordinates associated with Lake Mendota, which will be the largest object (by area) in the waterbody object.
data(mendota) <- which.max(st_area(mendota$sp$NHDWaterbody)) largest_waterbody <- mendota$sp$NHDWaterbody[largest_waterbody,] mendota_lake <- st_transform(mendota_lake, crs = 4326) mendota_lake <- st_coordinates(st_centroid(mendota_lake))mendota_centroid
Next, we can use the
extract_network function to pull the stream network associated with Lake Mendota. Notice that we have set the
maxsteps parameter to Inf. If the network is anticipated to be very large it can be a good idea to set this to a discrete (lower) number to avoid returning very large lines objects.
<- extract_network(lon = mendota_centroid, mendota_network lat = mendota_centroid, maxsteps = Inf)
Finally, we compare the stream network from a geometric buffer around Lake Mendota against the output of
extract_network to make sure everything is working properly.
ggplot() + geom_sf(data = mendota$sp$NHDFlowLine) + geom_sf(data = mendota_lake, fill = "cyan") + geom_sf(data = mendota_network, color = "blue")