Louisiana has laws on drainage in the civil code that state that a landlowner can't change the natural drainage of his property to either make his land drain unnaturally onto his neighbor's land or to keep his neighbor's land from naturally draining onto his property. The issue is not really the fence per se (assuming the fence is not over the property line), your issue is one of drainage, it sounds like. Look at the Louisiana Civil Code articles under Property. Somewhere in the 600's, I think. You will find some articles dealing with your issue.