Great Lakes Environmental Assessment and Mapping Project

Coastal Roads

Aerial view of Milwaukee, WI (Bing Maps, 2012)
Coastal roads in Milwaukee, WI on Lake Michigan. (Image: Bing Maps 2012)

Coastal roads provide access to the lake shore, including shoreline in less developed areas and sensitive habitats. Though similar to coastal development, roads are considered a distinct stressor because they:

  • Add to the amount of impervious, in impermeable, surrface area
  • Alter the nearshore physical and chemical environmnet by contributing run-off polluted with road surface materials (e.g., salt, sand)
  • Fragment habitats
  • Act as barriers to animal movement


Mapping coastal roads as a Great Lakes stressor

Canadian road data was derived from the Ontario Road Network.1 U.S. road data was derived from TIGER line files from the 2010 U.S. Census. For consistency, efforts were made to select paved roads from each dataset.2

The influence of coastal roads was assumed to extend one kilometer into the lakes. For each 1 km2 shoreline pixel, we computed the coastal road density (km road/km2) and assigned the value to the nearest water pixel. High coastal road density is generally correlated with high human population and high urban development.3


Spatial distribution of coastal roads as a stressor in the Laurentian Great Lakes (Inset: Southern Lake Michigan).



Data Sources: 

1. Ontario Ministry of Natural Resources. Ontario Road Network. 2005. Peterborough, Ontario, Canada.
2. U.S. Census Bureau. TIGER Line shapefiles. 2009. Washington, D.C., USA,
3. Lopez, R.D., D.T. Heggem, D.Sutton, T. Ehli, R.V. Remortel, E. Evanson, and L. Bice. 2006. Using Landscape Metrics to Develop Indicators of Great Lakes Coastal Wetland Condition. EPA/600/X-06/002. Washington, D.C., USA.