Not later than its last regular meeting of December, 1991, and every tenth year thereafter, the then incumbent Council must by ordinance redivide the Municipality into four wards or determine that no change in ward boundaries is necessary. Such an ordinance shall not be subject to veto by the Mayor. Wards so formed shall be composed of contiguous and compact territory within the Municipality bounded by street or railroad lines and natural boundaries, and shall be as nearly equal in population as shall be practicable, but wards shall not differ by more than ten percent by population from the smallest ward. Upon failure of the Council to establish such ward boundaries or to determine that no change in ward boundaries is necessary, the Mayor shall establish the ward boundaries as provided above and shall file such plan with the Clerk of Council and with the Summit County Board of Elections. This plan shall thereupon become the new division by wards of the Municipality.
   When any territory is annexed to the Municipality, Council shall by ordinance determine the contiguous ward or wards to which such territory shall be annexed.