On August 3, 1998, approximately 1500 mountain daylight time, a Cessna 182R, N5099E, sustained substantial damage when the pilot failed to negotiate a turn while taxiing from landing at Front Range Airport, Watkins, Colorado. The private pilot and his passenger sustained minor injuries. The flight was operating under Title 14 CFR Part 91 and no flight plan was filed for this cross-country flight which originated from Omaha, Nebraska, at 1200 central daylight time, with an intended destination of Centennial Airport, Englewood, Colorado. Visual meteorological conditions prevailed. According to the pilot, he was 40 miles from Centennial Airport when a level 6 thunderstorm was reported to be over the destination airport at the time of intended arrival. He made the decision to divert to Front Range Airport. He landed on runway 35 (8000 ft. x 100 ft., asphalt) and exited the runway. The pilot stated that the taxiway over to the terminal appeared to be approximately 2 miles away, and in order to save time, he taxied at a speed of 25 to 30 mph. There was a rise in the taxiway, and the pilot was unable to see the right taxiway exit in enough time to slow his taxi speed and execute a right turn. The aircraft departed the taxiway, and came to rest in a ditch west of the taxiway, approximately 15 feet below the taxiway pavement. Postaccident examination of the aircraft revealed that there was damage to the propeller, the engine, engine mount, and firewall. There was also damage to the landing gear, wing tips, and propeller.