Hi and welcome to JA. I am Ray and will be the expert helping you today.
Yes your neighbor has liability to you under the law of South Carolina under the Common Enemy Doctrine.
The Common Enemy Doctrine in South Carolina
The common enemy doctrine is a rule derived from English common law. It holds that since surface water is a "common enemy" to landowners, each landowner has the right to alter the drainage pattern of his land (for example by building dikes or drainage channels) without regard for the effects on neighboring parcels, as long as that water flows to where it otherwise would have naturally flowed.
Typically, a landowner can capture surface water (e.g. by rain barrels or dams) as well, and lower landowners will not have a cause of action unless the diversion is malicious. This rule is followed by approximately half the U.S. states, although some states have modified the doctrine to hold landowners liable for negligent damage to the parcels belonging to neighboring landowners.
Here the law in South Carolina - SC follows the common enemy rule with respect to the diversion of surface waters naturally flowing across land. Baltzeger v. Carolina Midland Ry. Co., 54 S.C. 242, 247-48, 32 S.E. 358, 360 (1899); The rule allows a landowner to treat surface water as a common enemy and dispose of it as the landowner sees fit. Glenn v. School Dist. No. Five of Anderson County, 294 S.C. 530, 533, 366 S.E.2d 47, 49 (Ct. App. 1988).
There are, however, two exceptions and this is where your neighbor has crossed the line.. First, the common enemy rule is subject to the law of nuisance and an individual may not obstruct or alter the flow of water to create a nuisance per se. Johnson v. Phillips, id. at 414, 433 S.E.2d at 899; Baltzeger v. Carolina Midland Ry. Co., id. at 247, 32 S.E. at 359-60. Second, except by contractual or prescriptive right, an upper landowner may not, by means of a ditch, impoundment or other artificial structure, collect surface water on his own land and cast it in a concentrated form upon lower adjoining land. Johnson v. Phillips, id. at 414, 433 S.E.2d at 899.
So yes you may sue the neighbor here for damages and an injunction forcing them to remedy the problem as well as legal fees, court costs, etc.
Your lawyer sends demand letter and unless they resolve this then you can pursue a civil suit.I hope you will do so here as the neighbor has clearly harmed you and violated the law.