Riddolls, B.W. 1971 Geology of Karioi hydro-electric project. Lower Hutt: New Zealand Geological Survey. New Zealand Geological Survey report EG 107 12 p.
Abstract: The proposed scheme involves a canal and several control dams that will divert water from Tokiahuru Stream to a power-house in the valley of the Whangaehu River. The geology consists of soft fine-grained Upper Tertiary sediments that are overlain by a thick succession of volcanic derived conglomerates, breccias, and ash. These lithologies should cause few difficulties during construction, but further information will be obtained from a forthcoming site investigation programme. On a wider scale, the area has been affected by large landslides, and the Whangaehu River is notorious for lahars (mud-flows) that are associated with sudden floods. While neither of these events occurs frequently, the possibility of their effecting the scheme in the future should be taken into account. (auth)