For the purpose of the chapter:
(A) Zone A shall consist of all land lying within or below the high-water mark in the reservoir sites, whether flooded or not. This zone includes tributary watercourses upstream to a distance of 1/2 mile from the high-water mark.
(B) Zone B shall consist of that portion of the drainage area within 100 feet of the high-water mark around the reservoirs and within the same distance of any of its tributaries extending upstream, following the channel of the stream, a distance of 1/2 mile from the high-water mark. This zone includes, at certain places, all land extending from the 100-foot limit to the top of the bluffs and to the end of the ravines where slopes are steep; provided the board of health or its duly authorized representative shall first notify, in writing, the owners and tenants of the bluffs and ravines.
(C) Zone C shall consist of the territory within 500 feet of Zone B as specified.
(D) Zone D shall constitute the remainder of the drainage area.
(E) The distances mentioned in Zones B, C, and D, shall be measured on a horizontal line from the high-water mark, except when otherwise specified. ('64 Code, § 36-3)