On August 16, 2002, about 1100 Pacific daylight time, a Cessna 185A, N4145Y, made a precautionary landing in a dry riverbed after colliding with a hilltop near Fillmore, California. The pilot/owner was operating the airplane under the provisions of 14 CFR Part 91. The airplane sustained substantial damage. The commercial pilot, the sole occupant, was not injured. Instrument meteorological conditions (IMC) prevailed for the cross-country flight that departed the Fresno Yosemite International Airport (FAT), Fresno, California, about 0930. The flight was scheduled to terminate at the Santa Paula Airport (SZP), Santa Paula, California. According to the pilot, he checked weather at FAT prior to departure. Because Santa Paula does not report weather, he checked nearby airports: Camarillo and Oxnard, California. He indicated that the weather at Camarillo and Oxnard was broken to overcast; however, from previous experience he believed that Santa Paula would be clear. The pilot felt that it would be a safe flight to make. When he arrived in the Santa Paula area, the clouds were lower than he had anticipated. He made a climbing right turn to get out of the clouds when he impacted a hill with the main landing gear. The pilot reported that the emergency locator transmitter activated. After he climbed out of the clouds he looked out the windows to assess the airplane damage. When he looked out the right window, he saw that the right landing gear was missing. The pilot stated that he would not be able to land at Santa Paula with missing landing gear because the runway width was small. Therefore, he chose to land in the riverbed. The National Transportation Safety Board investigator-in-charge reviewed the weather observation facility reports for Camarillo (located about 14 miles south of the accident site and 9 miles south-southeast of the destination airport), and Oxnard (located about 17 miles south-southwest of the accident site and 12 miles south of the destination airport). The reports revealed instrument meteorological conditions existed up to the time of departure with ceilings ranging between 400 and 1,000 feet and visibilities ranging between 1 to 5 miles. At 1055, the Camarillo weather observation facility reported a broken layer of clouds at 1,100 feet agl and an overcast layer of clouds at 1,300 feet agl with a visibility of 5 statute miles in haze. At 1155, the Camarillo weather observation facility reported the same cloud conditions with a visibility of 4 statute miles in haze. At 1051, the Oxnard weather observation facility reported an overcast ceiling at 1,100 feet agl and 3 statute miles visibility in haze. At 1128, Oxnard's weather observation facility reported a broken layer of clouds at 1,100 feet agl with a visibility of 2.5 statute miles in haze.