nhdplus_v2 — US river network (NHDPlus version 2.1)

Description

The rivers, streams, canals and other flowlines of the United States as represented by NHDPlus version 2.1 (the National Hydrography Dataset Plus) of the US Environmental Protection Agency and the US Geological Survey, which combines the medium-resolution (1:100,000) National Hydrography Dataset (NHD) with the National Elevation Dataset and the Watershed Boundary Dataset into a network of flowlines with flow directions and value-added attributes, such as the stream order, the drainage areas and estimates of the mean annual flow. It covers the conterminous United States, Hawaii, Puerto Rico and the US Virgin Islands, and the Pacific islands of American Samoa, Guam and the Northern Mariana Islands (not Alaska), and is distributed in 26 vector processing units (VPUs), which are combined here into a single network.

Nodes are the flowlines (identified by their COMID), and a directed edge goes from a flowline to each flowline downstream of it, as given by the flow table (PlusFlow) of NHDPlus, which is the basis of the navigation in the network (the connections across the boundaries of the processing units are included once). The network is not a forest of trees, since a flowline can have several flowlines downstream (divergences, e.g. in braided channels, deltas and canals; the main path is marked by divergence). Besides the flowlines of the network, the NHD contains flowlines that are not part of it (e.g. coastlines and some isolated or uninitialized features, without value-added attributes), which are included as nodes, marked by in_network (311,005 of the 3,035,617 flowlines, mostly canals and ditches and isolated streams; all of them but one are isolated nodes). The positions of the nodes are the downstream ends of the flowlines (whose geometries are digitized in the direction of flow), in NAD83 coordinates (which differ from WGS84 by about 1 m). The geometries, the catchments and the monthly flow estimates are not included.

The network has the following properties (missing values are -1, NaN or empty strings):

(Node) comid: the identifier of the flowline (COMID).
(Node) name, gnis_id: the name of the river or stream and its identifier in the Geographic Names Information System (GNIS).
(Node) reachcode: the 14-digit reach code of the NHD (whose first 8 digits are the hydrologic unit).
(Node) ftype, fcode: the type of the feature (e.g. StreamRiver, ArtificialPath, CanalDitch, Connector, Coastline, Pipeline) and its detailed code.
(Node) vpu: the vector processing unit of the flowline (e.g. 01, 03N, 10L).
(Node) in_network: whether the flowline is part of the network of NHDPlus (has value-added attributes).
(Node) length: the length of the flowline, in km.
(Node) stream_order: the Strahler stream order (modified for divergences); stream_calc: the stream order calculated without the minor paths of divergences (0 for these).
(Node) stream_level: the level of the stream (1 for the main paths that end at the coast or the Great Lakes, increasing for tributaries; -9 or 0 for coastlines).
(Node) hydroseq: the hydrologic sequence number (sorting the flowlines from downstream to upstream); level_path: the hydroseq of the most downstream flowline of the main path (level path) of the flowline; terminal_path: the hydroseq of the terminal flowline of its drainage network.
(Node) path_length: the distance from the end of the flowline to the end of its drainage network along the main paths, in km; arbolate_sum: the total length of the flowlines upstream, including this one, in km.
(Node) divergence: 0 for flowlines without divergence, 1 for the main path of a divergence, 2 for minor paths (9 for most coastlines).
(Node) start_flag, terminal_flag: whether the flowline is a headwater, or ends the drainage network.
(Node) area, total_area, divergence_routed_area: the area of the catchment of the flowline, its total drainage area, and its drainage area with the flow split at divergences, in km$^2$.
(Node) tidal: whether the flowline is tidal.
(Node) mean_flow, mean_velocity: the estimated mean annual flow (gage-adjusted, in cubic feet per second) and velocity (in feet per second) of the Enhanced Unit Runoff Method (EROM, not available for the Pacific islands).
(Node) slope: the slope of the flowline (m/m); max_elevation, min_elevation: the smoothed elevations of its ends, in m.
(Node) latitude, longitude: the position of the downstream end of the flowline.
(Edge) direction: the code of the connection in the flow table (709 for the connections between flowlines, 714 for the connections into coastlines, from rivers or between consecutive coastlines).
(Edge) delta_level: the difference of the stream levels of the flowlines.
(Edge) gap_distance: the distance across a gap between the flowlines, in km (0 for most).

Tags

Hydrology Spatial Unweighted Metadata

Added

2026-10-31

Citation

R. B. Moore, T. G. Dewald, "The Road to NHDPlus — Advancements in Digital Stream Networks and Associated Catchments." Journal of the American Water Resources Association 52, 890-900 (2016) 10.1111/1752-1688.12389 Sci-Hub
L. McKay, T. Bondelid, T. Dewald, J. Johnston, R. Moore, A. Rea, "NHDPlus Version 2: User Guide." US Environmental Protection Agency (2012) www.epa.gov

Upstream URL OK

https://www.epa.gov/waterdata/nhdplus-national-hydrography-dataset-plus
https://dmap-data-commons-ow.s3.amazonaws.com/index.html#NHDPlusV21/

Upstream license

Public domain (US government work), https://www.usa.gov/government-works

Networks

Tip: hover over a column header for a description.

Column legend

$\left<k\right>$: Mean degree
$\sigma_k$: Standard deviation of the degrees
$\lambda_h$: Largest eigenvalue of the Hashimoto (non-backtracking) matrix
$\tau$: Random walk mixing time
$r$: Degree assortativity
$c$: Global clustering coefficient
$\oslash$: (Pseudo-) diameter
$S$: Relative size of the largest component
NPs: Node properties
EPs: Edge properties

Name	Nodes	Edges	$\left<k\right>$	$\sigma_k$	$\lambda_h$	$\tau$	$r$	$c$	$\oslash$	$S$	Kind	Mode	NPs	EPs	gt	GraphML	GML	csv
nhdplus_v2	3,035,617	2,785,941	0.92	1.04	2.73	10429303.20	-0.17	0.00	12,184	0.62	Directed	Unipartite	comid vpu gnis_id name reachcode ftype fcode length longitude latitude in_network stream_order stream_calc stream_level hydroseq level_path terminal_path path_length arbolate_sum divergence start_flag terminal_flag area total_area divergence_routed_area tidal mean_flow mean_velocity slope max_elevation min_elevation	direction delta_level gap_distance	131.3 MiB	206.6 MiB	196.9 MiB	197.3 MiB