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Install: install.packages("hydroloom")

Or for latest development: remotes::install_github("doi-usgs/hydroloom")

hydroloom is a collection of functions to work with hydrologic geospatial fabrics. Hydroloom is designed to provide general hydrologic network functionality for any hydrographic or hydrologic data. The package intended for developers of workflows and other packages that require low level network and network data manipulation utilities.

To Learn More, visit the pkgdown site:


Blodgett, D., 2023, hydroloom: Utilities to Weave Hydrologic Fabrics,

Hyroloom has support for attributes that can be seen in:

Click to See Definitions
Name Definition
id shared network identifier for catchment divide and flowpath or flowline
toid indicates to the downstream id. May or may not be dendritic
fromnode indicates the node representing the nexus upstream of a catchment
tonode indicates the node representing the nexus downstream of a catchment
divergence indicates whether a catchment is not downstream of a diversion (0), the primary path downstream of a divergence (1), or a minor path downstream of a diversion (2).
wbid waterbody id
total_da_sqkm total drainage area at the outlet of a catchment
da_sqkm local drainage area of a catchment
length_km length of a single catchment’s flowpath
pathlength_km distance from the outlet of a catchment to the terminal outlet of a network
arbolate_sum total accumulated length of all upstream flowlines
topo_sort Similar to hydrosequence in NHDPlus. Large topo_sort values are upstream of small topo_sort values. Note that there are many valid topological sort orders of a directed graph.
up_topo_sort topo sort value of the upstream mainstem
dn_topo_sort topo sort value of the downstream mainstem
dn_minor_topo_sort topo sort value of the downstream minor network element with the smallest id
terminal_topo_sort topo sort value of the outlet network element
terminal_flag 1 for network terminous 0 for within network
terminal_id id of terminal catchment for entire drainage basin
start_flag 1 for a headwater, 0 otherwise
levelpath provides an identifier for the collection of flowpaths that make up a single mainstem flowpath of a drainage basin
up_levelpath levelpath value of the upstream mainstem
dn_levelpath levelpath value of the downstream mainstem
levelpath_outlet_id id of outlet catchment of a levelpath
stream_level starting at 1 for coastal terminals and 4 for inland terminals increments by 1 for each smaller tributary level
dn_stream_level stream level of downstream mainstem network element
stream_order starting at 1 for headwaters increments by 1 for each larger tributary level, divergences adopt stream order from upstream but returning divergent network does not increment stream order
stream_calculator starting at 1 for headwaters and 0 along diverted paths increments by 1 for each larger tributary level, does no increment along diverted paths. Is equal to stream_order along the dendritic network
feature_type descriptive feature type moniker
feature_type_code compact feature type identifier
vector_proc_unit identifier for processing units based on vector encapsulation
raster_proc_unit identifier for processing units based on raster encapsulation
id_measure interpolative linear reference measure along a single identified feature
aggregate_id aggregate identifier useful for ‘reach’ or ‘flowpath’ aggregation of flowlines
aggregate_id_measure interpolative linear reference measure along an aggregate feature
aggregate_id_from_measure interpolative linear reference for downstream end of a single feature that makes up an aggregate feature
aggregate_id_to_measure interpolative linear reference for the upstream end of a single feature that makes up an aggregate feature
point_id identifier of hydrologic location point
offset offset distance from point to line in units of linear reference analysis units

hydroloom supports your attribute names that map to the in-built definitions. See hydroloom_names() for more.

hydroloom supports both dendritic and non-dendritic networks start at this vignette for more.

hydroloom was largely created from components of nhdplusTools:

Blodgett, D., Johnson, J.M., 2022, nhdplusTools: Tools for
  Accessing and Working with the NHDPlus,

hydroloom will support some key functionality of nhdplusTools. Some components of nhdplusTools will be deprecated in a future version of the package in favor of the hydroloom implementation. In general, nhdplusTools will continue to support web service functionality and particulars of the NHDPlus data model. In contrast, hydroloom is intended to be more general and focused specifically on hydro fabric data functionality.

hydroloom implements algorithms documented in:

NHDPlus Attributes:

Moore, R.B., McKay, L.D., Rea, A.H., Bondelid, T.R., Price, C.V., Dewald, T.G., 
  and Johnston, C.M., 2019, User's guide for the national hydrography dataset 
  plus (NHDPlus) high resolution: U.S. Geological Survey Open-File Report 2019–1096, 
  66 p.,

Graph Concepts:

Cormen, T. H., & Leiserson, C. E. (2022). Introduction to 
  Algorithms, fourth edition. MIT Press.

Pfafstetter Attributes:

Verdin, K. L., & Verdin, J. P. (1999). A topological system for 
  delineation and codification of the Earth's river basins. 
  Journal of Hydrology, 218(1–2), 1–12.


The following definitions have been used as much as possible throughout the package.
Terms for rivers:
Flowline: A flowline is an linear geometry that represents a segment of a flowing body of water. Some flowlines have no local drainage area and are never aggregate features.
Flowpath: A flowpath is a linear geometry that represents the connection between a catchment’s inlet and its outlet. All flowpaths have a local drainage area and may be aggregates of flowlines.
Catchment: A physiographic unit with zero or one inlets and one outlet. A catchment is represented by one or more partial realizations; flowpath, divide, and networks of flowpaths and divides.
Catchment Divide: The polygon boundary that encompasses a catchment.

Design Notes:

  • Hydroloom uses tibble because dplyr verbs for data.frame was dropping the custom hy attributes.
  • The data.table package is used for some key joins to enhance scalability but dplyr is preferred for clarity.
  • hy class tibble standardizes all attribute names in code.
  • graph representation facilitated by make_index_ids() and make_fromids()
  • names are plural when referring to identifiers and singular when referring to a numerical attribute.


This software is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The software has not received final approval by the U.S. Geological Survey (USGS). No warranty, expressed or implied, is made by the USGS or the U.S. Government as to the functionality of the software and related material nor shall the fact of release constitute any such warranty. The software is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the software.