(1) The slope of the SMZ is measured perpendicular to the stream or lake from the ordinary high water mark to a point 50 feet slope distance from the ordinary high water mark.

(2) The SMZ width is 50 feet slope distance on each side of streams, lakes, and other bodies of water measured from the ordinary high water mark, in all cases except:

(a) where wetlands exist adjacent to the stream, lake, or other body of water, the SMZ extends to include the wetlands;

(b) on class 1 and 2 stream segments and lakes where the slope of the SMZ is greater than 35%, the SMZ width is 100 feet, except:

(i) where an established road exists between 50 and 100 feet from the ordinary high water mark, the SMZ boundary is located at the top of the road fill; or

(ii) where the slope of the SMZ decreases to 15% or less to form a bench that is 50 to 100 feet from the ordinary high water mark and at least 30 feet wide, the SMZ boundary is located at the edge of the bench nearest the stream.

(3) Where forest practices that are prohibited in the SMZ will be conducted adjacent to the SMZ boundary on a class 1 or class 2 stream segment, the SMZ boundary must be clearly marked prior to conducting such practices.