A watershed is the geographic region that drains into a body of water and is defined by the land forms and water flow. Hills and valleys direct water to a drainage basin such as a river or lake.

photo of Euclid Creek
Shaded waterways contribute to healthier ecosystems through cooler water temperatures.

The Rivers and streams of Cuyahoga County and their many tributaries give structure not just to the natural systems and ecology of the County, but also provide the underlying logic which shaped development patterns, including where we live, work, and play. Watersheds can be small – like the area that drains into the creek behind your house. Or, watersheds can be large – consider all the land, streams and rivers that drain into the Ohio River or Lake Erie.1 The Watersheds layer group provides two depictions of local watersheds:

  • Each of the local watersheds are named and grouped according to their major watershed “parent”; and
  • Local Watersheds by Percent Impervious: Watersheds are shaded according to the percentage of impervious surface, a key indicator of watershed health and guide for appropriate practices.

image of healthy valleyUrbanization often brings an increase in hard surfaces, or impervious cover, which changes watershed hydrology by increasing water runoff volumes. As rain falls on hard surfaces, such as rooftops and parking lots, it often picks up pollutants, delivering them directly to the stream and decreasing water quality. Reducing the amount of impervious cover in a watershed can help improve the water quality significantly. Studies conducted by the Center for Watershed Protection depict a correlation between impervious cover and stream degradation (see chart). The study found that an impervious cover greater than 25% can significantly damage stream functions and therefore reduce water quality. Every stream has a different threshold; however, generally speaking, the following conditions show a pattern and correlation.2

Percentage of
Impervious Cover
Level of
Water Quality
0-10% Sensitive Good Water Quality
Supports Aquatic Life
10 – 25% Impacted Marginal Water Quality
Can support aquatic life
Greater than 25% Damaged Poor Water Quality
Channel eroded or modified
Limited aquatic life

Importance and Value

Watersheds include the water features, wetlands, steep slopes and flat floodplains and thus share many of the same importance and value previously listed. Overall, healthy watersheds provide a variety of no-cost services to the communities including:

  • Stabilizing stream erosion,
  • Minimizing flooding,
  • Providing recreational opportunities.
  • Protecting the unique geography and natural history of the county.
  • Contributing to the aesthetic beauty of a community, making the County a more desirable place to live, work and visit.

Recommendations for Communities and Land Ownersimage of Willow West Creek

  • Develop a state endorsed Balanced Growth Watershed Plan.
  • Limit soil erosion on construction sites through best management practices (minimize extent of disturbance, temporary seeding, etc.) to keep soil particles in place, reducing the amount of sediment in a stream.
  • Re-establishing natural infiltration, e.g. allowing water to filter through the soil as it does naturally through creation of rain gardens or bioswales.
  • Separate storm sewers and sanitary sewers to eliminate the combined sewer overflow problems.
  • Restore the natural biological and physical systems of a watershed through tree plantings, bioengineering, floodplain enhancement, etc.
  • Remove invasive species and plant native species to help increase biodiversity.
  • Develop green connections between various beneficial natural areas (e.g. parks) to ensure wildlife movement and migration throughout the County.
  • Utilize Low-Impact Development practices that help to mimic the natural environment and ensure pre-development hydrology is reached at site completion.

Resources for More Information

1 Ohio EPA: Total Maximum Daily Load (TMDL) Program
2 Impacts of Impervious Cover on Aquatic Systems: Watershed Protection Research Monograph, Center for Watershed Protection