NLDI Flowtools

Version: 0.3.8

Basin delineation and flow path tracing for any point within CONUS, powered by NHDPlus V2 data and the Network Linked Data Index.

from nldi_flowtools.nldi_flowtools import splitcatchment, flowtrace

# Delineate the full upstream drainage basin
basin = splitcatchment(lon=-93.0, lat=45.0, upstream=True, simplified=True)

# Trace the flow path to the nearest stream
trace = flowtrace(lon=-93.0, lat=45.0, direction="down")

Both functions accept WGS 84 longitude/latitude coordinates and return GeoJSON FeatureCollections.

Tools

Split Catchment — Identifies the NHD catchment containing a point and delineates the upstream contributing area. Can return either the local split portion or the full upstream drainage basin merged with all upstream catchments.

Flow Trace — Follows the 30m flow direction grid downhill from a point until it intersects an NHD stream. Returns the traced raindrop path and the intersected stream segment (upstream, downstream, or full geometry).

Tip

When delineating a point on a stream, run it through flowtrace first to snap the point to the flowline. Use the returned intersection point as input to splitcatchment for the most accurate basin boundary.

Installation

pip install nldi-flowtools

Requirements: Python 3.10 – 3.14.

For development setup, see the Contributor Guide.

Authors

Anders Hopkins — Lead Developer — USGS Web Informatics & Mapping

Acknowledgments