La. Stat. tit. 38 § 1641
All bridges and enlargements of existing bridges, shall be built or enlarged according to the plans and specifications approved by the chief engineer of the district. Where the bridges are outside of the drainage district the Department of Public Works shall first approve the plans and specifications therefor.
All new bridges and all enlargements of existing bridges made necessary by the work of reclamation shall be built or enlarged at the expense of the drainage district. All new bridges built at the expense of the drainage district shall be maintained by the drainage district. Any increased cost of maintenance of existing bridges occasioned by any enlargement thereof made by a drainage district shall be borne by the drainage district.
Any owner of land within or without the district, desiring to do so, may, at his own expense, and in compliance with the terms and provisions of this Part, construct a bridge across any drain, ditch, canal, or excavation in or out of the district.
All drainage districts may construct and maintain any ditch or lateral provided in the plan for reclamation across any of the public highways of this state, without proceedings for the condemnation of the highways, or being liable for damages therefor. Within ten days after having completed a ditch across any public highway, the drainage district shall construct and maintain a bridge over the ditch where the ditch crosses the highway.
All drainage districts when deepening, enlarging, or cleaning out any natural drain in or out of the district shall remove any bridge, flume, or other work in, over, or under the natural drain, without the necessity of condemnation or of paying damages therefor. The bridge, flume, or other work shall be replaced by the drainage district within a reasonable time and at its own expense.
La. R.S. § 38:1641