On September 12, 1997, at 1545 Alaska daylight time, a Piper PA-12 airplane, N2389M, sustained substantial damage when it nosed over during landing at a gravel bar on the Theodore River, about 25 miles west of Anchorage, Alaska. The private certificated pilot and one passenger sustained minor injuries. The flight was conducted under 14 CFR Part 91, as a personal flight from Merrill Field in Anchorage, to the Theodore River, and returning. The flight departed Merrill Field at 1335. Visual meteorological conditions prevailed at the time of the accident, and no flight plan was filed. The pilot reported he was landing to the west with an approximate 30 degree right crosswind of four knots. The airplane was just above touchdown, at an indicated airspeed of 30 to 35 miles per hour, with full flaps extended, when the airplane settled. He stated the airplane landed hard, the tail came up, and the prop struck the ground. The airplane nosed over onto its back. Photographs of the landing site reveal a stand of trees just to the right of the approach end of the landing area. The airplane was configured with 8.50 x 6 inch tires. Photographs of the gravel bar reveal two 6 inch wide gouges in the sand beginning below the lip of the river bank, and continuing onto the landing area. Between these gouges are four slash marks oriented approximately 45 degrees to the gouges, spaced about equally in the line of airplane travel.