The Buller River is a river in the South Island of New Zealand. The Buller has the highest flow of any river in the country during floods, though it is only the 13th longest river; it runs for 177 km (110 mi) from Lake Rotoiti through the Buller Gorge and into the Tasman Sea near the town of Westport. A saddle at 710 m (2,330 ft) separates the Buller from the Motupiko River and that is divided from the Wairau River by a 695 m (2,280 ft) saddle, both aligned along the Alpine Fault, as is the top of the Buller valley.

The Stillwater Ngākawau Line (SNL), formerly the Stillwater–Westport Line (SWL) and the Ngakawau Branch, is a secondary main line, part of New Zealand's national rail network. It runs between Stillwater and Ngakawau via Westport on the West Coast of the South Island. It was one of the longest construction projects in New Zealand's history, with its first section, at the south end, opened in 1889, and the beginnings of the Ngākawau Branch, at its Westport end, in 1875. The full line was completed in 1942. The only slower railway projects were Palmerston North to Gisborne, 1872 to 1942, and the Main North Line to Picton, 1872 to 1945.