For the general purpose of refunding all or any part of the bonded indebtedness, now or hereafter outstanding, of any drainage or levee district now or hereafter organized and existing under any law of this state, whenever in the judgment of the county legislative body of the county in which any such district was organized, it is advisable and for the best interest of the landowners of any such district, or whenever such district is or hereafter shall become unable to pay all or any part of the principal and interest or either the principal or interest of or on its outstanding bonded indebtedness, the county legislative body may issue refunding bonds of such district in an amount that shall not exceed in the aggregate the amount of bonds to be refunded, and the accrued interest on the bonds. Such refunding bonds shall be of such denomination or denominations, shall mature at such time or times, not exceeding forty (40) years from their date, and in such manner, amount or amounts, shall be payable at such place or places, and shall bear such rate of interest payable annually or semiannually as the county legislative body may determine. Such refunding bonds may be exchanged for the bonds to be refunded upon consent of the holders of the bonds, or may be sold at such price and in such manner as the county legislative body may determine. Any expense resulting from the sale or issuance of such refunding bonds may be paid out of any available funds of the district. If the outstanding bonds have not matured, they may be refunded only with the consent of the holder or holders of the bonds, which consent shall be sufficiently evidenced by the surrender of the bonds to be refunded. Such refunding bonds shall be signed by the county mayor and countersigned by the county clerk, under the seal of the county or the seal of such clerk, and the interest coupons attached to the bonds shall be executed by the lithographed facsimile signature of the officials.