La. R.S. 38:1603

When it seems desirable in the opinion of the parish governing authorities acting on their own initiative, to create drainage districts composed of contiguous lands situated partly in one parish and partly in one or more adjoining parishes, the drainage district may be created either by joint resolution of the respective governing authorities of the parishes or by an ordinance of the governing authority of one of the parishes approved by the governing authority of the other parish or parishes.