According to the pilot, he performed about 20 touch-and-go landings on the dry lake bed prior to the accident. He stated that the terrain was mostly flat, but in places it was uneven and rough. During the last landing, the airplane's wheels became bogged down in the terrain, and the propeller struck the ground. The pilot shut down the engine, inspected the propeller, and examined the planned takeoff path for suitability. Thereafter, he attempted to depart. As the airplane accelerated, the left main landing gear encountered an area of soft dirt. The airplane impacted a berm whereupon it nosed over, bending the wing structure and the vertical stabilizer. The pilot further reported that no mechanical malfunction had precipitated the accident.