Uses a raindrop trace web service to trace the nhdplus digital elevation model to the nearest downslop flowline.

`get_raindrop_trace(point, direction = "down")`

- point
sfc POINT including crs as created by:

`sf::st_sfc(sf::st_point(.. ,..), crs)`

- direction
character

`"up"`

,`"down"`

, or`"none"`

. Controls the portion of the split flowline that is returned along with the raindrop trace line.

sf data.frame containing raindrop trace and requested portion of flowline.

```
# \donttest{
point <- sf::st_sfc(sf::st_point(x = c(-89.2158, 42.9561)), crs = 4326)
(trace <- get_raindrop_trace(point))
#> Simple feature collection with 2 features and 7 fields
#> Geometry type: LINESTRING
#> Dimension: XY
#> Bounding box: xmin: -89.21572 ymin: 42.94986 xmax: -89.20944 ymax: 42.95699
#> Geodetic CRS: WGS 84
#> # A tibble: 2 × 8
#> id gnis_name comid reachcode raindrop_pathDi… measure intersection_po…
#> <chr> <chr> <int> <chr> <dbl> <dbl> <list>
#> 1 downstr… Yahara R… 1.33e7 07090002… 273. 29.7 <dbl [2]>
#> 2 raindro… NA NA NA NA NA <dbl [0]>
#> # … with 1 more variable: geometry <LINESTRING [°]>
bbox <- sf::st_bbox(trace) + c(-0.005, -0.005, 0.005, 0.005)
nhdplusTools::plot_nhdplus(bbox = bbox, cache_data = FALSE)
#> Spherical geometry (s2) switched off
#> although coordinates are longitude/latitude, st_intersects assumes that they are planar
#> Spherical geometry (s2) switched on
#> Spherical geometry (s2) switched off
#> although coordinates are longitude/latitude, st_intersects assumes that they are planar
#> Spherical geometry (s2) switched on
#> Spherical geometry (s2) switched off
#> although coordinates are longitude/latitude, st_intersects assumes that they are planar
#> Spherical geometry (s2) switched on
#> Spherical geometry (s2) switched off
#> Warning: No waterbodies features found
#> Spherical geometry (s2) switched on
#> Spherical geometry (s2) switched off
#> although coordinates are longitude/latitude, st_intersects assumes that they are planar
#> Spherical geometry (s2) switched on
#> Zoom: 15
#> Map tiles by Carto, under CC BY 3.0. Data by OpenStreetMap, under ODbL.
#> Audotdetect projection: assuming Google Mercator (epsg 3857)
plot(sf::st_transform(sf::st_sfc(point, crs = 4326), 3857), add = TRUE)
plot(sf::st_transform(sf::st_geometry(trace)[1], 3857), add = TRUE, col = "red")
plot(sf::st_transform(sf::st_geometry(trace)[2], 3857), add = TRUE, col = "black")
# }
```