On June 20, 2000, at about 2042 eastern daylight time, a Bell OH-58A, N913SP, registered to the Georgia Department of Public Safety, operating as a public-use flight, rolled over on its right side after landing in the vicinity of Rome, Georgia. Visual meteorological conditions prevailed and no flight plan was filed. The helicopter sustained substantial damage. The commercial pilot reported serious injuries. The helicopter was on the ground running when the accident occurred. The pilot stated he had just landed at an unimproved field site after conducting a drug eradication flight to let his aerial observer out of the helicopter. He thought he had landed on flat terrain; however, the left skid was located on a rut. He lowered the collective pitch to the full down position and the throttle remained at 103 percent. The observer unbuckled his seat belt and shoulder harness and exited the helicopter through the left door. As soon as his body weight was off of the helicopter and onto the ground, the left skid came off the ground, and the helicopter rolled over on its right side before he could take any corrective action. Review of FM 1-203, Fundamentals of Flight states, a helicopter is susceptible to a lateral rolling tendency called dynamic rollover. This dynamic rollover can occur on level ground; however it is more likely to occur and more hazardous during slope or crosswind landing and takeoff maneuvers. Dynamic rollover starts when the helicopter has only one skid or wheel on the ground. That gear may become the pivot point for lateral roll. When this happens, lateral cyclic control response is more sluggish and less effective than a free-hovering helicopter. (For additional information see Fundamental of Flight, an attachment to this report.)