add_lake_context: Add Lake Context from NHD

In lakefetch: Calculate Fetch and Wave Exposure for Lake Sampling Points

Add Lake Context from NHD

Description

Add hydrological context to fetch results using the National Hydrography Dataset (NHD). Includes outlet/inlet locations, watershed area, connectivity classification, and stream order.

Usage

add_lake_context(fetch_results, lake_polygons, utm_epsg)

Arguments

fetch_results	sf object with fetch calculation results
lake_polygons	sf object with lake polygons
utm_epsg	EPSG code for UTM projection

Details

Requires the nhdplusTools package. If not available, returns the input with NA columns added for consistent output format.

Added columns include:

• nhd_permanent_id: NHD permanent identifier

• nhd_gnis_name: GNIS name from NHD

• nhd_areasqkm: Area in square kilometers from NHD

• outlet_dist_m: Distance to outlet in meters

• outlet_bearing: Compass direction to outlet

• inlet_nearest_dist_m: Distance to nearest inlet

• inlet_nearest_bearing: Compass direction to nearest inlet

• inlet_count: Number of inlets

• connectivity_class: Headwater/Drainage/Terminal/Isolated

• outlet_stream_order: Strahler stream order at outlet

• watershed_area_ha: Watershed area in hectares

• lake_watershed_ratio: Lake area / watershed area

Value

sf object with additional columns for NHD context

Examples

csv_path <- system.file("extdata", "sample_sites.csv", package = "lakefetch")
sites <- load_sites(csv_path)
lake <- get_lake_boundary(sites)
results <- fetch_calculate(sites, lake)
results_with_context <- add_lake_context(results$results, results$lakes, lake$utm_epsg)

lakefetch documentation built on March 20, 2026, 5:10 p.m.