Rocky Creek Dam - Location and Features

Location and Features

Commenced in 1949 and completed in April 1953, the Rocky Creek Dam is a minor dam located in the Northern Rivers region of New South Wales, situated approximately 25 kilometres (16 mi) north of Lismore. The dam is the principal component of the Rous Water bulk supply network for the region, experiencing population growth. The dam as built by Dayal Singh under contract to the Rous County Council.

The dam wall is made up of about 80,000 tonnes (79,000 long tons) of rock, soil, clay and concrete and is 28 metres (92 ft) high and 220 metres (720 ft) long. At 100% capacity the dam wall holds back 14,000 megalitres (490×10^6 cu ft) of water at 187 metres (614 ft) AHD. The surface area of Rocky Lake is 200 hectares (490 acres) and the catchment area is 31 square kilometres (12 sq mi) which includes the Whian Whian State Forest, Nightcap National Park and Whian Whian State Conservation area. The area was once used for logging but is now has a conserved and generally pristine catchment environment. The uncontrolled spillway is capable of discharging 730 cubic metres per second (26,000 cu ft/s).

The vegetation in the catchment is mainly subtropical rainforest or wet sclerophyll. The vegetation community generally reflects the geology and soils in the area which are derived from the Lamington Volcanics which in this area consists of basalt and thick rhyolite rocks erupted from or associated with the Tweed Volcano. The subtropical rainforest is generally regarded as one of the biggest remnants of the Big Scrub rainforest that once existed over a large part of the surrounding region.

The dam is considered small compared to the size of the population it services. However, the secure yield is high because of the catchment's climate with its consistent high annual rainfall. The nearby Rummery Park rain gauge formerly operated by the Bureau of Meteorology has the highest average annual rainfall in New South Wales. However, in 2003 the lack of rain meant that the water level was at one stage less than twenty per cent.

In 2009 the dam wall was upgraded by ensuring the safety of the dam wall during a maximum probable flood. The upgrade involved the removal of the top of the wall, the installation of a concrete cut-off wall keyed into the impermeable clay core, followed by replacement of the gravel and road over the dam wall.