The pilot was taking off from a gravel bar in a tailwheel-equipped airplane with a load of light, bulky cargo items. The gravel bar was in a valley location surrounded by mountainous terrain. He said that the wind indicators along the strip favored the takeoff direction, which was the same direction he had used for landing earlier. He stated that all felt normal during the takeoff roll, but the airplane encountered "a gust from behind or above" upon rotation. The airplane subsequently settled back to the surface and struck brush near the end of strip, turned, and came to a stop across a small ditch. The airplane sustained substantial damage to the right wing and the aft section of the fuselage. The pilot stated that there were no preaccident mechanical anomalies with the airplane that would have precluded normal operation. The pilot reported that, right after the accident, he observed that the wind became very gusty to about 20 mph. He noted that the wind condition returned to light and variable in less than an hour.