The pilot reported that just after takeoff he hovered the helicopter about two feet above the ground before starting a northwesterly takeoff run over an area of grass-covered, uneven terrain. The pilot noted that during the takeoff run, the main rotor RPM began to decay, so he added engine throttle to correct for the RPM decline. The helicopter subsequently descended and during touchdown, the left main landing gear skid collapsed. The helicopter rolled to the left, and the main rotor blades struck the ground. The helicopter sustained substantial damage to the main rotor drive system, tail boom, and fuselage. The pilot reported that the estimated gross weight of the helicopter at takeoff was 2,300 pounds, or approximately 50 pounds under the maximum gross weight of 2,350 pounds. The density altitude was calculated to be 7,015 feet mean sea level. The pilot reported no preaccident mechanical malfunctions or failures with the helicopter that would have precluded normal operation.