On February 1, 1997, at 1115 central standard time, a Cessna 182, N2898R, operated by a private pilot collided with a ditch following a loss of directional control while landing on runway 16 at the El Dorado Thomas Airport, El Dorado, Kansas. The 14 CFR Part 91 personal flight was operating in visual meteorological conditions without a flight plan. The airplane was substantially damaged and the pilot was not injured. The flight originated from Ponca City, Oklahoma, at 1035 cst. The pilot reported that after touching down on runway 16 the airplane began to veer to the right side of the runway. He reported that he was unable to straighten the direction of travel. The right main landing gear traveled off the side of the runway into soft terrain. The pilot reported that it seemed as if the right wheel was sliding and that this action pulled the airplane even more to the right. The airplane traveled into a ditch located approximately 30 feet off the side of the runway. The ditch was described as being 5 to 6 feet deep. The pilot reported the airplane heading was almost perpendicular with the ditch when it contacted it. The airplane was removed from the ditch by an A&P/IA. He stated that the wheels turned smoothly with no binding noted as the airplane was moved. The A&P/IA further inspected the brake system and reported he was unable to find any mechanical discrepancies which would have resulted in the loss of directional control.