La. Stat. tit. 38 § 438
For the purpose of providing a sinking fund to meet the payment of the principal of the bonds issued under this Subpart, the levee board or levee and drainage board, beginning ten years before the maturity of the bonds, shall levy annually to an amount sufficient for that purpose, the taxes and local contributions which it is authorized and empowered to levy and which they may be hereafter authorized to levy. From the first money realized from the taxes and local contributions, the state treasurer, after providing for the payment of the interest of the bonds, shall set apart annually, beginning ten years before the maturity of the bonds, an amount sufficient to pay ten percent of the bonds outstanding. The money thus set apart shall not be diverted to any other purpose, except the purchase of outstanding bonds.
La. R.S. § 38:438