DURING THE TAKEOFF ROLL, THE AIRPLANE STRUCK SEVERAL LARGE ROCKS CAUSING THE MAIN LANDING GEAR TO TEAR AWAY FROM THE FUSELAGE. AS A RESULT OF THE MAIN LANDING GEAR BEING RIPPED AWAY, THE AIRPLANE'S MAIN WING SPAR AND STABILATOR WERE DAMAGED. AFTER THE PILOT DEPARTED THE BEACH AREA, HE FLEW DIRECTLY BACK TO KING SALMON AIRPORT.