WCC 1995 plan excerpts

This page contains information taken from the Wellington City Council's Trelissick Park Management Plan June 1995.

Landform and geology

Prior to the formation of the gorge, the area was part of an extensive peneplain extending from Makara to Khandallah. The present landform developed from earthquake and erosion activity, resulting in the formation of the gorge. A characteristic feature of the peneplain remnant is the rounded forms of the higher slopes contrasting quite dramatically with the steeper erosion-formed valley sides.

While the landforms in the park appear to be typically those of a valley landscape, in reality the landforms are considerably more complex and varied. Within the park there is a series of quite dramatic bluffs, spurs, steep rock faces and outcrops along with a series of ravine-like side valleys. Some of the more visually striking landforms and rock outcrops are above and on the south side of the Kaiwharawhara Stream on land which is not currently in the park. However, visually these areas form an integral part of the park landscape. Generally the landforms in the Kaiwharawhara Stream valley are more dramatic and visually striking than those in the Korimako Stream valley.

Geologically the area consists of variably weathered, fractured and jointed sandstones and argillites. Bedrock slopes are carved by thin colluvium and solifluction deposits. The soils are yellow-brown Ngaio, Korokoro and Makara hill soils, and Ngaio silt loam over greywacke. The soils are reasonably fertile and very well drained.

Climate

The elevation of the park is low relative to the surrounding topography, affording some degree of shelter and comfort. The site is reasonably protected from southerly winds, but it is exposed to strong winds from the north to west quarter. Being in a steep-sided gorge the area experiences longer than usual periods of shade and cooler temperatures particularly in the winter months. On calm summer days temperatures can be very warm in the gorge. Generally the gorge landscape offers a range of micro-climates that adds to and enriches the attraction and diversity of the area.

Utilities

Trelissick Park is strategically important for stormwater and sewer services in the northwestern suburbs. The Kaiwharawhara and Korimako Streams are a major stormwater system draining the valley from Karori and Northland to the south, Ngaio and Khandallah to the north. In the park there are also a number of stormwater pipes, culverts and open streams which discharge stormwater into the Kaiwharawhara and Korimako streams. A stormwater tunnel under the railway embankment takes the flow from the Kaiwharawhara Stream in the Otari/Wilton area to the main stream, which is a combination of the Korimako and Kaiwharawhara streams. A recently upgraded sewer pipe is located in the tunnel.

Major sewer lines which convey sewage flow from Wilton, Crofton Downs and parts of Khandallah and Karori to the main sewer interceptor pass beneath the park. The 450 and 525mm diameter pipelines were replaced in 1984. As a consequence of this work there are some lengths of abandoned pipe lying in the park. There are also older sewer pipes towards the eastern end of the park, taking the flow from Wadestown. Upgrading of these pipes are planned for the 1994/95 financial year. While most of the sewer lines are underground there are places throughout the park where pipes and manholes are quite visible. Two grill-covered tunnel portals can be seen from the main track when walking beside the Kaiwharawhara Stream. Generally the sewer infrastructure in the park is visible but not generally obtrusive.

The 110kV Khandallah to Wilton transmission line passes over the park. Pylons are located on the Northern Walkway spur below Trelissick Crescent and on the area below Oban Street in Highland Park.