What is EDT?

 
EDT, or Ecosystem Diagnosis and Treatment, is a system for rating the quality, quantity, and diversity of habitat along a stream, relative to the needs of a focal species such as coho or chinook salmon. The methodology includes a conceptual framework for decision-making and a set of modeling tools with which to organize environmental information and rate the habitat elements with regard to the focal species. In effect, EDT describes how the fish would rate conditions in a stream based on our scientific understanding of their needs. EDT has been used extensively in the Pacific Northwest for a number of years in a variety of settings.

The value of EDT is that it can identify the potential for a stream under a set of conditions such as those that occur now or those that might occur in the future. The result is a scientifically based assessment of conditions and a prioritization of restoration needs.

Because each segment, or stream reach, is rated individually, we can systematically examine conditions along a stream from the perspective of the fish. In this way, we locate areas where conditions are particularly good or bad and identify things that need to be fixed. In particular, EDT identifies the "restoration potential" and the "protection value" of each reach. This helps us prioritize actions and focus them on areas with identified problems and where the potential for benefit is highest. Below is an example of an EDT output depicting the protection and restoration priorities for a small stream.

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