On November 5, 1998, 1043 central standard time, a Mooney M20J, N1073K, collided with a ditch following a loss of directional control while landing on runway 30L (6,997' x 100') at the St. Louis Downtown-Parks Airport, Cahokia, Illinois. The private pilot was not injured. The airplane was substantially damaged. The 14 CFR Part 91 instructional flight was operating in visual meteorological conditions without a flight plan. The flight originated from the St. Louis Downtown-Parks Airport, at 0955 cst. The pilot reported that he checked the ATIS prior to returning to the airport for landing at which time the winds were being reported as 020 degrees at 10 knots. He reported he centered the airplane over the runway by using a "lot of left rudder and right aileron." The pilot reported the airplane touched down "perfectly", but he was unable to control the "snake-like" motion of the airplane during the landing roll. He reported that instead of over controlling the airplane he decided to let it travel off the left side of the runway into the grass. He reported that there was a ditch in front of him and to minimize the impact he added power in an attempt to fly over it. He continued to report that due to the tailwind, he was unable to clear the ditch and the propeller hit the terrain. Post accident inspection of the airplane by an inspector from the Federal Aviation Administration St. Louis, Missouri, Flight Standards District Office revealed the ditch was approximately 6 to 7 feet deep and 30 to 40 feet wide. The inspector reported the airplane contacted the far side of the ditch approximately two feet below the top of the ditch. The airplane traveled another 60 to 75 feet prior to coming to a stop. The main landing gear were separated from the airplane and the nose gear had collapsed. Holes were punctured in the wings at the main gear attach points. Both the nose and cowling area were wrinkled. Reported local winds 9 minutes after the accident were from 050 degrees at 13 knots.