The pilot was operating a sightseeing hot air balloon flight with eleven passengers. According to pilot statement, the approach was flown to a standard company landing field. During approach to landing, winds unexpectedly shifted from 330 degrees at eight knots to 110 degrees at speeds up to 18 knots. As the easterly winds decreased to approximately 12 knots, the pilot elected to continue the approach into an unplanned landing area and informed the passengers to prepare for a high wind landing by bending their knees and holding on to the rope handles tightly. According to the pilot, the hard landing occurred at approximately 12 knots groundspeed, in an open area with uneven terrain. Of the eleven passengers on board, one suffered a fractured ankle. The pilot reported no pre-impact mechanical malfunctions or failures with the balloon that would have precluded normal operation.