The private pilot was attempting to fly over a 1,200 foot long, gravel-surfaced site before landing. He reported that as he maneuvered the airplane for the fly over, he applied 10 degrees of wing flaps, and a "downdraft came over the wings and stalled them both... ." The airplane subsequently struck the ground in a nose down attitude, and came to rest about 200 feet from the approach end of the intended landing site. The airplane sustained structural damage to the wings, fuselage, and empennage. The pilot noted that there were no preaccident mechanical anomalies with the airplane.