The pilot of the helicopter reported that, while flying in mountainous terrain, he decided to land on top of a ridge for a rest break. The pilot performed a circling reconnaissance of the area before he began his descent to his intended landing spot. During the descent, the pilot felt a wind gust from behind, then the rotor rpm began to decay, and the low rotor rpm light illuminated along with the aural warning horn. The pilot attempted to reestablish power without success as the helicopter continued to descend. To avoid going over the ridge, the pilot intentionally lowered the helicopter to the ground and rolled the helicopter onto its right side. The helicopter sustained substantial damage to the fuselage and tail boom. The pilot reported that there were no preaccident mechanical failures or malfunctions with the helicopter that would have precluded normal operation.