[1] The name comes from the Māori word hāpuku or hāpuka, a deep-water marine fish.

[8] Whilst other rivers were affected by serious flooding in 1953, the Hāpuku rose only 6.5 ft (2.0 m) at the railway bridge.

[9] Presumably this was due to the short catchment, the tectonic uplift of its headwaters and the width of the braided river bed, which is a source of railway ballast.

[12][13] Wildlife associated with the area include black-eyed geckos, found near the headwaters of the north branch Hāpuku River,[14] and bluff wetas.

[16] Introduced species include red deer, goats (kept at low levels by culling), pigs and chamois.