Whenever it becomes necessary, because the corporate limits of the City have been extended or contracted, the City Council shall redistrict the city into wards, change the boundaries of existing wards, or increase or diminish the number of wards.
But in no case shall the City Council redistrict the city into wards or change the boundaries of existing wards, except insofar as it may be necessary to maintain wards which meet the test of equitable population distribution, or to change such boundaries for the purpose of attaching newly annexed territory of such existing ward or wards as may be contiguous thereto, more often than once every five years, except upon a recorded vote of three-fourths of the members elected to the council; and in every such case the reason therefor shall be set forth in the ordinance providing for such redistricting.
