If the improvement contemplated by this chapter is ordered to be made upon the immediate payment plan, the city council shall provide for the payment thereof by the issuance of local improvement fund warrants against the local improvement district, which warrants shall be paid only out of the funds derived from the local assessments in the district and shall bear interest at a rate determined by the city council from date of issuance. If the improvement is ordered to be made upon the bond installment plan, the city council shall provide for the issuance of bonds against the improvement district.