The pilot was landing on a remote off-airport site in a tailwheel-equipped airplane. He stated that the landing area was on a 15-degree slope. The landing was uneventful, but shortly after stopping the airplane, a gust of wind turned the airplane so the nose was pointing down the hill. The airplane began rolling down the slope, and then nosed over. The airplane sustained substantial damage to the vertical stabilizer, rudder, and wing. The pilot reported that there were no preaccident mechanical anomalies with the airplane that would have precluded normal operation.