lakefetch

Calculate fetch (open water distance) and wave exposure metrics for lake sampling sites.

Overview

lakefetch calculates directional fetch using a ray-casting algorithm, can download lake boundaries from OpenStreetMap, and provides exposure classification for ecological and limnological studies. Unlike marine-focused packages (fetchR, waver), lakefetch is designed specifically for freshwater lakes with features like multi-lake batch processing and NHD integration.

Installation

Install the development version from GitHub:

# install.packages("devtools")
devtools::install_github("jeremylfarrell/lakefetch")

Quick Start

library(lakefetch)

# Load your sampling sites (CSV with latitude/longitude columns)
sites <- load_sites("my_sites.csv")

# Download lake boundaries from OpenStreetMap
lake <- get_lake_boundary(sites)

# Calculate fetch for all sites
results <- fetch_calculate(sites, lake)

# View results
results$results  # sf object with fetch data and exposure categories

Features

• Automatic boundary download: Downloads lake polygons from OpenStreetMap with multi-server fallback
• Ray-casting fetch calculation: Measures distance to shore in all directions at configurable resolution
• Multi-lake support: Process sites across multiple lakes in a single analysis
• Exposure classification: Automatic categorization into Sheltered/Moderate/Exposed
• NHD integration: Optional integration with National Hydrography Dataset for US lakes (outlets, inlets, watershed area)
• Weather integration: Weather integration is optional and disabled by default during package checks
• Visualization: Static plots (maps, bar charts, rose diagrams) and interactive Shiny app

Example Workflow

library(lakefetch)

# Use built-in example data
data("adirondack_sites")

# Get lake boundaries
lake <- get_lake_boundary(adirondack_sites)

# Calculate fetch
results <- fetch_calculate(sites = adirondack_sites, lake = lake)

# Visualize results
plot_fetch_map(results)
plot_fetch_bars(results)

# Launch interactive app (requires shiny, leaflet)
fetch_app(results)

Key Functions

Function	Description
load_sites()	Load sampling sites from CSV
get_lake_boundary()	Download lake boundaries from OSM or load from file
fetch_calculate()	Calculate directional fetch and exposure metrics
plot_fetch_map()	Map of sites colored by exposure category
plot_fetch_bars()	Bar chart of effective fetch by site
plot_fetch_rose()	Directional fetch rose diagram for a site
fetch_app()	Interactive Shiny app for exploration

Output Metrics

For each sampling site, lakefetch calculates:

• Directional fetch: Distance to shore at each angle (default: 10° resolution)
• fetch_mean: Mean fetch across all directions
• fetch_max: Maximum fetch (longest open water distance)
• fetch_effective: Mean of top 3 fetch values (primary exposure metric)
• exposure_category: Sheltered (<2.5 km), Moderate (2.5-5 km), or Exposed (>5 km)

Using Local Boundary Files

If you have your own lake boundary shapefile or geopackage:

lake <- get_lake_boundary(sites, file = "my_lake_boundary.shp")
results <- fetch_calculate(sites, lake)

Optional Features

NHD Integration (US lakes only)

# Requires nhdplusTools package
# install.packages("nhdplusTools")

results <- fetch_calculate(sites, lake, add_context = TRUE)
# Adds: outlet location, inlet locations, watershed area, connectivity classification

Weather Integration

# Add historical wind data for wave energy calculations
# Requires a datetime column in your sites data
results <- add_weather_context(results$results, datetime_col = "datetime")

Example Datasets

The package includes example datasets for testing:

• adirondack_sites: Sampling sites from Adirondack lakes (New York)
• wisconsin_lakes: Lake boundaries from Wisconsin
• example_lake: Single lake polygon for testing

Citation

citation("lakefetch")

License

MIT License

Contributing

Issues and pull requests are welcome at GitHub.