On June 10, 1995, about 1600 Alaska daylight time, a float equipped Champion 11BC-S airplane, N86135, sustained substantial damage when it collided with terrain shortly after takeoff from an unnamed lake located approximately 20 miles south of Anchorage, Alaska. The commercial pilot received serious injury. The one passenger aboard was not injured. The personal flight operated without a flight plan in visual meteorological conditions. The flight's intended destination was Kenai, Alaska. The pilot reported he was attempting to takeoff from a small lake in gusty wind conditions. He estimated the winds at 10 knots, gusting to 18 knots from the north. He said he made a step turn taxi from the south to the north, to make a northerly takeoff run. Soon after takeoff, he said he encountered a downdraft and realized he had low airspeed and minimal altitude above the brush-covered terrain. He lowered the nose of the airplane to increase airspeed, but in the process lost altitude and collided with terrain. The pilot reported no preimpact mechanical anomaly with the airplane.