The helicopter had been chartered because the passenger's farm had been isolated by flood waters. The crew carried out a survey of the area before landing to check the suitability of the chosen site. Shortly after take-off, the aircraft collided with a power line which was about 25 feet agl, and then struck the ground heavily about 15 metres beyond the line. Both the pilot and the crewman reported that they had sighted the power line during the survey prior to landing. However, the pilot subsequently forgot the presence of the line and conducted a shallow climb after take-off. Because the rear seat cushions were wet, the passenger was placed in the front seat, while the crewman occupied a rear seat. When he became aware that the helicopter was climbing at a shallow angle, he reminded the pilot to beware of the wires. The pilot then saw the power line directly ahead of the aircraft, but was unable to avoid the collision.