The pilot reported that he was performing external load long line hauling operations with a helicopter and was on a return leg with two empty nets. During the approach to a hilltop helipad, the pilot reported that he performed a normal approach, rather than a long line approach. Subsequently, the 100 foot long line snagged on a ridgeline and the helicopter jerked in an uncontrollable turn to the right, touched down right skid first, and rolled over. The pilot reported that he forgot that the long line was still attached. The tail boom was substantially damaged. The pilot did not report any mechanical malfunctions or failures with the helicopter that would have precluded normal operation. The operator submitted two operator/ owner safety recommendations to the National Transportation Safety Board investigator-in-charge. First, the operator revised the normal operation checklist. The revised checklist included a new "CARGO HOOK – CHECK" in both the BEFORE TAKEOFF and DESCENT AND LANDING checklist. Second, the chief pilot provided a copy of a memorandum to all employees that directs the use of an observer, when available, to observe the takeoff and landings and communicate any unsafe condition to the pilot via radio communication or hand signals.