The board of township trustees of any township located in a county having a population of more than six thousand three hundred (6,300) and less than six thousand five hundred (6,500) and an assessed valuation of more than thirty-five million dollars ($35,000,000), may annually levy a tax of not to exceed two (2) mills for the purpose of creating a special fund for maintaining dams and other structures necessary for flood control. No such tax shall be levied unless and until the question of levying the same shall have been submitted to and approved by a majority of the qualified voters of such township voting thereon at a regular township election.