According to the pilot, there was a slight depression in the narrow, paved strip used for glider takeoffs, and that during the takeoff roll, the left wing “flexed” and “dipped” such that the wingtip contacted the turf which created the pivot point around which the glider “ground-looped” which fractured the empennage aft of the cockpit. The pilot added that there had been “3 weeks of heavy rain” prior to the day of the accident and that the grass on either side of the takeoff strip was longer than usual, which reduced his wingtip clearance. He stated that while he had successfully departed the strip earlier that day, a lower grass height would have lowered his risk exposure during the takeoff run. The pilot reported that there were no pre-accident mechanical malfunctions or anomalies that would have precluded normal operation.