(1) Part of the Watershed plan in its respective county;

(2) Any part to cover 1 or more sections of the Watershed within its respective county; or

(3) 1 or more of the other functional subject matters to be included in the plan.

(b) Before adopting the plan or any part, extension, amendment, or addition to it, the appropriate county governing body or its duly designated agency shall hold at least 1 public hearing. Thirty days notice of the time and place of the hearing shall be given by publishing a notice once in a newspaper of general circulation in the affected county. Adopting, amending, extending, or adding to the plan or any part of the plan shall be by resolution. The resolution expressly shall refer to the maps and other descriptive matter, which the appropriate county governing body or its duly designated agency intends to form the whole or part of the plan. Any action taken shall be recorded on the map, plan, or descriptive matter by the identifying signatures of the appropriate county official. The appropriate county governing body or its duly designated agency shall certify an attested copy of the plan or any part, amendment, extension, or addition to the plan and file it with the clerk of the circuit court for the county affected.