Said cities shall have the power to issue bonds to pay for any lands acquired, and the wharves and improvements constructed thereon, when authorized by a vote of the people at a general election or any special election held for that purpose, and said bonds to be serial bonds over a period not to exceed thirty (30) years, and to bear interest not to exceed the maximum rate of interest prescribed by Kan. Stat. Ann. § 10-1009. Bonds issued in pursuance of this act shall never exceed one percent (1%) of the assessed valuation of said city.