Big Darby Creek Watershed

What is an ecological risk assessment?

An ecological risk assessment evaluates the potential adverse effects of human activities on the plants and animals that make up ecosystems. The risk assessment process provides a way to develop, organize and present scientific information so it is relevant to environmental decisions. When conducted for a particular place such as a watershed, the ecological risk assessment process can be used to identify vulnerable and valued resources, prioritize data collection activities, and link human activities with their potential effects. Risk assessments provide a focal point for cooperation among local communities and state and federal government agencies, and a basis for comparing various management options.

Why is Big Darby Creek special?

The Big Darby watershed is a freshwater, aquatic ecosystem encompassing 1,443 sq km (557 square miles) in central Ohio. It is drained by Big Darby Creek, Little Darby Creek and a dozen smaller tributaries. The watershed is an example of a high quality ecosystem relatively free of pollution. A significant portion of Big Darby Creek is an Ohio State Scenic River and National Scenic River. The 129 kilometer (80 mile) long stream is widely recognized as home to an exceptional variety of species, including many rare and endangered freshwater mussels and fish. Big Darby Creek has been designated by The Nature Conservancy - an international conservation organization - as one of the "Last Great Places" in the western hemisphere. Awareness of the value of this unique resource, and growing concern about its future, has resulted in a partnership of over forty public agencies and private organizations. The partners share the goal of developing a cooperative approach toward the protection and maintenance of this valuable resource.

How can this valuable resource be protected?

This ecological risk assessment will analyze the stressors and resulting ecological effects in the Big Darby Creek watershed. The assessment promotes community awareness of ecological problems in the watershed and will provide information to resource managers, including government officials, organizations and the public. These activities promote environmentally beneficial results.

How is the ecological risk assessment being done?

Interested organizations collectively developed a management goal and developed a scientific study approach. The ecological risk assessment brought together numerous organizations to analyze the impact of stressors on the watershed. Measurements of watershed condition will be plotted on maps and related to land use within the watershed. Relationships between the stressors caused by land use activities and effects on fish and aquatic invertebrates will be examined. This will provide information to estimate risks associated with land-use decisions. A report describing the management goals for the watershed and the analysis plan for the assessment will be available upon completion of the analysis described above.

Key stressors being evaluated in the ecological risk assessment are:

  • sedimentation
  • nutrient enrichment
  • changes in water flow
  • changes in the physical characteristics of the stream channel
  • loss of tree cover adjacent to the stream
  • chemical contamination

How will the results be used?

The Big Darby Creek Watershed Ecological Risk Assessment will help resource managers predict how changes in land use and river flow will affect biological communities in the watershed. This will enable resource managers to make decisions based on more information. This project is co-sponsored by the USEPA's Office of Water and Office of Research and Development as an effort to bring the science of risk assessment into the local community decision-making process.


Cormier, S. AND M. Smith. Big Darby Creek Watershed. U.S. Environmental Protection Agency, Washington, DC, EPA/630/R-96/006A, 1996.

Additional Information

The U.S. Environmental Protection Agency thanks the following for their participation in this case study:

US Geological Survey
Ohio Department of Natural Resources
Ohio Environmental Protection Agency
The Nature Conservancy
Ohio State University Extension