The Clutha's first dam: the Nil Desperandum project at Quartz Reef Point, 1864-66

Abstract

The first dam on Central Otago's Clutha River was not the 1956 Roxburgh dam, but a gold-mining enterprise's structure built ninety-three years earlier. If it had succeeded, it would be lauded with other colonial-era New Zealand engineering feats such as the Denniston Incline and Raurimu Spiral; because it failed, it is forgotten. In 1864, two years after the goldfield began, miners organized Cromwell businessmen as shareholders to form the Nil Desperandum Company. Where the Clutha was bifurcated by Knobby Island at Quartz Reef Point they would build a timber crib cofferdam at each end of the island and pump the enclosed space dry to mine the riverbed. The upstream structure was to be built at 45° to the flow, 270 metres long, 15 metres thick and 7.5 metres high, constructed from timber frameworks filled with stone and backed by an additional rockfill buttress. This paper discusses this engineering feat, including how it was built, what it achieved and when the methodology was used elsewhere in New Zealand.