get_huc4 returns a SpatialPolygonsDataFrame of the HUC4 regions within
the specified template. If template is not provided, returns the entire HUC4 dataset.
get_huc4(template = NULL, raw.dir)A SpatialPolygonsDataFrame of the HUC4 regions within
the specified template.
A Raster* or Spatial* object to serve as a template for cropping.
A character string indicating where raw downloaded files should be put. The directory will be created if missing.