On July 25, 2006, at 1145 Pacific daylight time, a Cessna 182D, N8961X, experienced a loss of engine power and during the forced landing in a dry riverbed, the airplane collided with rocks at Santa Clarita, California. The private pilot and one passenger were not injured; the airplane sustained substantial damage. The pilot, who was also the registered owner of the airplane, was operating it under the provisions of 14 CFR Part 91. Visual meteorological conditions prevailed and no flight plan had been filed. The flight departed from Cameron Airpark, Cameron Park, California, at 0920. A Federal Aviation Administration (FAA) inspector from the Van Nuys, California, Flight Standards District Office responded to the accident scene. The airplane came to rest upright. The nose landing gear sheared from its mount and the firewall was buckled. The left wing was pulled aft into the fuselage of the airplane. Monarch Air fuel caps secured the intact fuel tanks. The right fuel tank contained a residual amount of fuel, and a large blue fuel stain was present on the right wing that ran from the filler neck aft and descended over the flap area. The o-ring on the right fuel cap was split. The left fuel tank was empty and there was a light fuel stain that ran approximately 6 inches aft of the tank filler neck. The left fuel cap o-ring was intact and the cap appeared to be securely fastened to the fuel tank. There was no further evidence of light blue staining on the airplane structure. The pilot stated that he topped off his fuel tanks at Cameron Airpark and departed at 0920 using the left tank. After approximately 2 hours, the engine began to sputter so he switched to the right fuel tank and initiated a descent from 7,500 feet mean sea level. After 10 minutes, the engine began to run rough so he switched the fuel selector to the both position, applied full mixture, full throttle, and carburetor heat. The engine would not restart and he force-landed the airplane in a dry riverbed. The airplane collided with rocks during the landing.