On May 29, 1996, at 1800 central daylight time, a Champion 7GCBC, operated by a private-instrument rated pilot, nosed over following a loss of directional control on landing at the Des Moines International Airport, Des Moines, Iowa. The 14 CFR Part 91 flight was not operating on a flight plan. The airplane was substantially damaged and the pilot was not injured. The local flight originated from Osceola, Iowa, at 1650 cdt. The pilot reported that he must have flared "to flat" because the airplane touched down hard and bounced back into the air during landing. He stated he added power to "smooth out the ensuing touchdown." He reported that he must have inadvertently applied the brakes during the landing and that is what caused the airplane to veer off the south side of the runway. The airplane traveled into a ravine where it nosed over upon contacting a ditch at the bottom of the ravine.