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Streamflow Duration Assessment Method for the Pacific Northwest

SDAM for Oregon

The Streamflow Duration Assessment Method (SDAM) for Oregon is a scientific, rapid-assessment field tool developed to help determine whether a stream is perennial, intermittent or ephemeral.  This tool has been developed for use in Oregon to provide technical guidance when identifying waters that may be subject to the regulatory jurisdiction under Oregon's Removal-Fill Law and Section 404 of the Clean Water Act.

The method was developed by experts from federal and state agencies with experience across Oregon, and reflects the technical expertise and critical review of others from relevant academic and professional fields. The interim method was released on March 6, 2009, for a trial implementation period. The method has been field tested by interagency teams of state and federal scientists, and was also the subject of a two-year validation study, in cooperation with EPA’s Office of Research and Development, Western Ecology Division, testing the method at more than 170 sites in western and eastern Or egon in both the wet and dry seasons. As a result of that study, the initial 21 field indicators used in the interim version were reduced to just seven reliable indicators in the final version. 
Use of the method is recommended whenever there is uncertainty regarding streamflow duration, but is not required. The method provides a scientifically supported, rapid assessment framework to support best professional judgment in a consistent, robust, repeatable and defensible way. Use of the method may result in more timely and predictable jurisdictional determinations. The method may also provide an initial framework to inform other stream-related issues such as stream function and compensatory mitigation, and to incorporate relevant tools and procedures as they develop.

NOTE: further field testing of the Streamflow Duration Assessment Method for Oregon supports its applicability in Idaho and Washington. The U.S. EPA and U.S. Army Corps have replaced the Oregon manual with a regionally consistent manual: Streamflow Duration Assessment Method for the Pacific Northwest. That method is substantively the same as SDAM for Oregon, and either may be used in Oregon.
Documents & Resources:

For more information, contact:

Tracie Nadeau, Environmental Protection Agency, 503-326-3685, Nadeau.Tracie@epa.gov
Peter Olmstead, Corps of Engineers, 541-962-0401, peter.d.olmstead@usce.army.mil 
Peter Ryan, Department of State Lands, 503-986-5232, Peter.Ryan@state.or.us