The pilot reported that he was on a local flight in mountainous terrain. While returning to the airport he began a descent by reducing power to about 60 percent, which resulted in a complete loss of engine power. The pilot applied full carburetor heat and full throttle and the engine regained power. He continued a shallow descent with full throttle and carburetor heat for about another 5 minutes. He closed the carburetor heat and continued the descent at 75 percent engine power. Within less than a minute, the engine lost complete power again. The pilot applied carburetor heat and full throttle, along with mixture adjustments and pumping the throttle, but the engine did not restart. He attempted a forced landing to a local highway. During the final approach, he avoided power lines by flying under them, but he was unable to flare the airplane before touchdown. The nose strut assembly sheared off during the landing and the right wing struck an embankment which resulted in substantial damage. The weather conditions at the time of the accident were conducive to serious carburetor icing during a descent.