In the “Whanganui National Park Management Plan

Ngā āhua whenua

4.1.1 Long-term outcome

The Whanganui National Park landscape is preserved as closely as possible to its natural state.

4.1.2 Description

Geology

The geomorphology of the Park results from the geological uplift of early seafloor sediments formed during the Tertiary period. The oldest of these sediments are geologically quite young – about 30 million years old. The age of the sediments underlying the landscape decreases progressively towards the coastline at Whanganui. The area only finally thrust itself clear of the sea about 1 million years ago, as is evident from the numerous fossils seen in the elevated sediments of the river valley (Smale, 1995). This process, together with the major lowering of sea levels during the last ice age (between 80,000 and 15,000 years ago) has created the steep, sharp ridges of fairly uniform height and deeply entrenched dendritic (tree-like) drainage pattern, which are a key characteristic of the Park's topography.

A journey down the Whanganui River is also a journey through geological history, as this sequence of sedimentary strata is progressively revealed as the river cuts through it on the way to the sea.

The only hard rocks are the occasional limestone beds and calcareous concretions within the more sandy beds, which occur throughout the area. The difference in hardness and permeability of the sediment controls the rate of erosion, which in turn affects slope stability. In some places caves have formed in the limestone beds. Examples of such caves can be seen near the 'Drop Scene' on the Whanganui River, north of Pīpīriki.

Volcanism has also influenced the landform of the Park. Ash showers from the Taupō eruption 1850 years ago, and later from Taranaki and Tongariro, mantled much of the area with a fine layer of ash. The Whanganui River and its tributaries have carried pumice alluvium and deposited it on many river terraces.

General landscape

Nearly half of the Park is less than 300 metres above sea level, but higher points such as Mount Humphries reach over 700 metres. The Matemateāonga Range forms a dominant topographic feature northwest of Pīpīriki. The vegetation cover of mostly unmodified forest has developed across a landform, which has eroded over 20,000 years since the last ice age. Its sheer expanse is visually impressive and the relatively uniform ridge heights give the opportunity to experience uninterrupted panoramic views of extensive tracts of primary lowland forest, stretching from Mount Taranaki in the west to Ruapehu in the east.

The gorge scenery produced by the water courses cutting down through the soft underlying sediments is often spectacular.

Northern section

South of Taumarunui to Rētaruke, the Whanganui River is deeply entrenched into its original valley floor with occasional narrow terraces. Between Taumarunui and Marae-kōwhai the northern outliers of the Park form part of a wider landscape that is a mosaic of pastoral hill country with remnant and revegetating native vegetation and introduced trees. Willows are noticeable on the immediate river margins. Roads follow the river in this part of the Park. These cultural modifications contribute to a different landscape setting, which offers different experiences from the wilder, more natural sections to the south.

Central 'core' section

The central section or core of the Park is highly valued for the maturity, continuity and intactness of its landscape, with the natural landscape expressing the underlying geology across large tracts of primary lowland forest. The natural landscape is predominant and the sense of remoteness and isolation is profound.

The Whanganui River flows in an almost unbroken narrow winding gorge in this section of the Park, giving fine examples of entrenched meanders. This landscape provides a sense of enclosure and intimacy, as well as isolation, for those travelling this section of the river.

However, the history of human occupation, particularly along the main river valleys, also provides a rich thread of historical markers and associations that is interwoven through this fabric. Physical signs include the remnant earthworks of numerous pā and kāinga, old landings and groves of introduced trees, notably Lombardy poplars. Plantations of pine and bare hillsides give an occasional reminder that pastoral farming dominates beyond the Park and in enclaves within it. Old road formations, reverting native bush and the remains of old house sites also provide a cultural dimension to its particular sense of place. These are poignant reminders of brief attempts to harness nature during the 'soldier's settlement era' and the signs of the enduring relationship between tāngata whenua and their tūpuna throughout the Park and along the river corridor in particular. These features (and reminders) carry strong values for New Zealanders and are of great interest to visitors.

Many minor tributaries meet the Whanganui and other main rivers as hanging valleys, producing both small and larger spectacular waterfalls, such as Waterfall Creek in the Mangapurua Valley.

Southern section

South of Pīpīriki, steep gorges alternate with more open areas and wider terraces. Here the Park again forms part of the mosaic of natural, cultural and pastoral landscape that makes up the lower Whanganui. The Ātene Block provides a wild and natural backdrop, a strong reminder of the lowland New Zealand landscape as it was before human settlement. Winding round the hill Puketapu, the old bed of the Whanganui River is clearly visible as a 'cut off meander' (the Ātene Oxbow), which is one of the best examples in New Zealand, and is included in the Geological Society of New Zealand’s Geopreservation Inventory2.

Whanganui National Park from Ātene Skyline Walk. Photo: A. Dijkgraaf.
Whanganui National Park from Ātene Skyline Walk

4.1.3 Management considerations

These landscape values are at the core of the Park's identity and are integral to its natural ecosystems. They also provide the scenic values that attract people to the Park. National park status provides strong safeguards against wholesale changes through major development or land use changes. General Policy 4.5 (b) states that activities that diminish the quality of scenic, geological (including geothermal), soil and landform features and other abiotic diversity within national parks should be avoided. This includes the cumulative effects of smaller scale activities.

Since its establishment, the Park has not been subject to any large scale effects arising from new human activities or uses. However potentially significant landscape changes could result from developments such as new large scale forestry, dams, accommodation facilities or major road cuttings within or adjacent to the Park.

The main aim during the plan period will be to continue to keep the Park in as natural a state as possible, whilst seeking to manage the impacts of past human uses on the landscape, notably the introduction of exotic plants and animals and the effects of past vegetation clearance.

4.1.4 Objectives

  1. To retain the Park in its natural state, free, as far as practicable from the effects of negative human-induced activities.
  2. To preserve and restore the natural features and scenic qualities of the Park for their intrinsic, scientific and educational values, and for the experience of nature and 'natural quiet' that they provide.
  3. To advocate for the preservation of landscape, geological features and landforms in areas adjacent to the Park, features of which contribute to the Park's natural or recreational values.

4.1.5 Policies

  1. Preservation of the natural and scenic qualities of the Park landscape and its 'natural quiet' will be the primary consideration in all decisions by the Department and in its recommendations on decisions to be made by the Minister with respect to any activities that have potential to affect its values.
  2. The Department will also advocate for the preservation and restoration of these values from the potential adverse effects of other activities, arising outside the Park, through a combination of advocacy, seeking appropriate additions to the Park, and formal submissions under the Resource Management Act 1991 and other relevant legislation.

Footnotes

2Note: Much of the above Landscape sections has been reproduced from Smale, 1995

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