WCC 1995 Plan Excerpts

This page contains some information extracted from the Wellington City Council 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 within the park appear to be typically those of a valley landscape in reality the landforms are considerabl y more complex and varied. Within the park there are 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 l and which is not currently within the park. However, visually these areas are seen as 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 thus affording some degree of shelter and comfort. However while the site is reasonably protected from southerly winds 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 within 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 with regard to 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 , to Ngaio and Khandallah to the north. Within 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 from 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 within 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 within the park. There is also a length of older sewer pipe of varying ages towards the eastern end of the park. This pipe takes the flow from Wadestown. Upgrading works on this pipelines are planned in the 1994/95 financial year. While most of the sewer lines are underground there are locations throughout the park where pipelines 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 within the park while quite visible it is 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.