Great Lakes Environmental Assessment and Mapping Project

Marinas and recreational boating

Great Lakes marina (Michigan Sea Grant)

Marinas are a potential source of chemical pollution due to boat maintenance activities and spillage of a variety of compounds that are harmful to aquatic organisms, including oil and gasoline.  They may also lead to physical effects on the environment associated with boat wakes, propeller action, harbor dredging, breakwaters and shoreline structures.


Mapping marinas as a Great Lakes stressor

  • Marina locations were identified from internet sites and the number of boat slips was obtained from marina websites when available or were counted using aeriel images.
  • Marinas located within river-inland lake complexes were included if within 5 km of a Great Lake.
  • We identified 726 marinas grouped into 504 locations around the Great Lakes, with an estimated 102,251 marina slips.

Based on the finding that 93% of boat slips in marinas with zip codes that border the Great Lakes were occupied in 20041, the estimated number of boats docked in marinas on the Great Lakes is 95,093.


The influence of marinas was scaled using the count of boat slips and assumed to dissipate to 10% of their initial value within 2.5 km and to 1% within 5 km. Once boats leave the harbor their effect is assumed to be negligible.


Spatial distribution of marinas and recreational boating as a stressor in the Laurentian Great Lakes (Inset: Western Lake Erie).


Data Sources: 

1. U.S. Army Corps. of Engineers. 2008. Great Lakes Recreational Boating. Detroit, Michigan.