La. Stat. tit. 38 § 1674.6
The board of commissioners of any drainage district complying with the provisions of R.S. 38:1674.1 through R.S. 38:1674.10 shall be and is hereby authorized to issue, execute, negotiate, sell and deliver negotiable interest bearing drainage certificates of the district in an amount not exceeding the total amount of the installments or deferred payments, as provided for in R.S. 38:1674.5, said certificates to bear interest at a rate or rates not exceeding the maximum rate provided for conventional interest by the Louisiana Civil Code as the same now exists or may be hereafter amended, payable annually, and to mature serially over a period not exceeding twenty years, but in no event shall said certificates extend over a longer period of time than that provided for by the ordinance levying the local or special assessments which may be payable in annual installments. Said certificates shall be of such form, date, denomination and payable in principal and interest at such time and place as the board may determine, and such certificates shall be secured by and payable in principal and interest from the irrevocable pledge and dedication of the funds derived from the levying and collection of the said local or special assessments, as hereinabove provided, and which funds shall be set aside in a separate fund and shall not be drawn upon for any other purpose than to pay the principal and interest of said certificates. Said certificates shall be issued in compliance with the provisions of Article X, Section 13 of the Louisiana Constitution and shall be secured as therein and herein provided.
La. R.S. § 38:1674.6