A Practical Approach to Cumulative Impact Assessment


D J. Stout

Publication Date



ISBN 0-913235-37-7

Publication Title

Proceedings of the Symposium on Small Hydropower and Fisheries

Start Page


End Page



Olson FW;White RG;Hamre RH;

Publication Place

Bethesda, MD


American Fisheries Society


More than 60 sites have been proposed for hydropower projects in Washington State's Snohomish River Basin within the last several years. In an attempt to provide for reasonable hydropower development that is compatible with fishery and wildlife management goals, the responsible Federal and State agencies and Indian tribes developed a procedure for project impact assessment. This procedure has been presented in the Snohomish Guidelines for the Evaluation of Hydropower Projects that (1) outlines parameters to be evaluated for each project, (2) recommends techniques to be used in assessing each parameter, and (3) describes an approach for the sequential analysis of project-specific and cumulative impacts. At this time, the Snohomish Guidelines have been used to analyze two projects. The Guidelines have provided a clear framework within which to evaluate these hydropower proposals. Agency and tribal biologists are required to establish management goals, make precise recommendations regarding assessment techniques, and set 'thresholds of significance' for the evaluation of study results. Project proponents are required to do detailed studies on selected parameters, and present the data in terms of a 'project impact zone' to allow analysis of potential cumulative impacts. The result is a clear path by which the acceptability of projects can be evaluated for impacts both project-specific and cumulative.

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