During approach the pilot was distracted by the proximity of trees and wires near the threshold. He allowed the speed to deteriorate and an excessive rate of descent to develop which he did not arrest. The aircraft landed heavily dislodging the nose wheel. The nose wheel mount tube dug into the surface of the strip and the aircraft overturned. The two occupants escaped without injury. Significant Factors. The following factors were considered relevant to the development of the accident. 1. The pilot was not aware of the degrading airspeed, possibly due to channelised attention. 2. The aircraft developed a high rate of descent. 3. The pilot did not arrest the high rate of descent. 4. The aircraft landed heavily and the nosewheel broke off.