IN THE MATTER Of the Resource Management Act 1991
AND
IN THE MATTER Of hearings in relation to proposed District Plan Change 32 and proposed District Plan Change 33
STATEMENT OF EVIDENCE OF Dr JOHN ALLEN McCONCHIE
1.0 INTRODUCTION1.1 I am a Senior Lecturer with the School of Earth Sciences at Victoria University of Wellington. I hold a Bachelor of Science degree with first class honours, and a Ph.D degree in physical geography from Victoria University of Wellington. I am a member of the New Zealand Hydrological Society, the American Geophysical Union, and the New Zealand Geographical Society. I teach undergraduate courses in geomorphology and hydrology, and a post-graduate course in hydrology and water resources. For more than 20 years my research has focused on various aspects of geomorphology and hydrology including: geomechanics, soil-water interactions, hydraulic modelling, and slope and surface water hydrology.
1.2 Within these fields I have edited one book, and written or co-authored 10 book chapters and 40 refereed scientific publications.
1.3 Specifically, I have written two chapters on the geomorphic interpretation and understanding of the Wellington landscape for international texts. I was an author of Landforms and geological features: a case for preservation published by the Nature Conservation Council in 1988 and was involved with the production of the New Zealand Landform Inventory published in 1990.
1.4 For three years I coordinated the investigation and field studies into the effect of hydro-electric operations on the geomorphic processes of the Waikato River. This was part of the Assessment of Environmental Effects required as part of Mighty River Power Ltd's resource consent application to operate the Waikato hydro system.
2.0 EXECUTIVE SUMMARY
3.0 GEOMORPHIC SIGNIFICANCE
3.1 Quartz Hill is a unique geomorphological feature consisting of an upland surface of low relief known as a peneplain. It is clearly separated from the surrounding landscape by steep headwaters of streams that drain to the surrounding valleys. The streams draining across Quartz Hill are themselves unique, being the 'youngest' river channels in Wellington.
3.2 Quartz Hill is by far the most extensive, and best-preserved, remnant of an ancient erosional peneplain that once existed throughout the Wellington region. The long-term processes associated with tectonic deformation and erosion have modified the majority of this surface so that in most places it is now visible only to the trained eye.
3.3 This ancient erosion surface was first recognised by C.A. Cotton who published a paper describing the feature, with particular reference to its occurrence at Mt Kaukau and Quartz Hill, in 1912.
3.4 Cotton (1912) described Quartz Hill as 'an undulating surface of mature valleys and rounded spurs, appearing from a distance perfectly plain .. [and] bounded on all sides by the slopes of young ravines eating into it'. The contrast in topography between the hill top and hill sides is extreme.
3.5 After almost half a century of research on the geomorphology of the Wellington region, during which time he became the world authority on the geomorphology of actively deforming regions, Cotton published a paper introducing the term 'K-surface' for the feature (Cotton, 1957). The letter 'K' stood for 'key', as the K-surface was the basic geomorphological unit by which deformation in the region could be measured. More recently, the 'K' has often been interpreted incorrectly to having referred to Mt Kaukau which is located on the surface to the north of Wellington.
3.6 The geomorphic significance of Quartz Hill has therefore been recognised by the international scientific community for almost 100 years.
4.0 GEOLOGIC BEGINNINGS
4.1 The sandstone and mudstone rocks underlying Quartz Hill are commonly referred to as greywacke of the Torlesse group. These rocks are typical of the old hard sedimentary rocks that make up the alpine backbone of New Zealand. They belong to a group known as the Rakaia terrane, and as such can be linked to similar rocks in the South Island from which they have been displaced by fault movement. The rocks date from the Permian and Triassic periods of the Mesozoic age. Judging by the extremely rare fossil shellfish, tube-worms, and microfossils in the rocks they may be up to 240 million years old.
4.2 The rocks are composed of predominantly feldspar and quartz mineral grains. The latter was remobilised by the high overburden pressure and temperature associated with these sediments being buried at depth. The quartz was then re-precipitated in cracks within the rock forming veins that sometimes contain traces of gold. Hence the historic gold mines and mine shafts in the Makara area.
4.3 During the Tertiary Period (45-35 MY ago) central New Zealand was not located on an active plate boundary and experienced a long period of tectonic quiescence. The landscape, uplifted during the previous tectonically active phase (Rangitata Orogeny) was eroded, in perhaps a classic Davisian cycle of erosion, to form an extensive peneplain close to sea level. This has been broken, folded, tilted, elevated to various levels, and progressively destroyed by subsequent erosion until today it is represented only as remnants on the flattish crests of some ridges. The erosion surface, however, provides dramatic evidence of the scale and rate of geomorphic change.
4.4 At Quartz Hill hundreds of metres of rock have been eroded to expose these once deeply buried quartz veins. The degree of quartz emplacement, as well as attempts to exploit the associated gold, make Quartz Hill unusual in the Wellington region.
5.0 ORIGIN OF THE SURFACE
5.1 The present-day K-surface was undoubtedly formed by the erosion processes. Although the exact nature of the erosive forces is not yet clear; they were probably a combination of fluvial, slope, and marine processes; the extent and nature of the surface mean that they must have operated over a considerable period of time. The forces must have also acted over a very wide area judging by the original size of the surface and the fact that the eroded material was deposited outside the Wellington region.
5.2 Because the surface lies at the top of the landscape, its origin was clearly early in the development of Wellington’s present landscape. The actual age of the surface is unknown. The only clues come from the age of the oldest sediments sitting on top of the surface (a little over 1 million years) and the age of the sediments that underlie the surface (3.6-5.0 million years for marine sediments at Makara).
5.3 Since the greywacke rocks that form the K-surface are commonly weathered to a depth of 50m the surface must have been stable for a considerable period of time.
6.0 SUBSEQUENT MODIFICATION
6.1 Since the K-surface was formed, it has been deformed by tectonic processes. It has been folded and faulted, uplifted and downwarped so that its elevation varies considerably across Wellington. In Wellington City it is near sea level, and presumably below sea level. To the west and north of the city it often forms the crests of ridges.
6.2 Since the activity of any faults younger than the K-surface displace, and disrupt, the surface it provides a useful reference horizon from which to assess the relative age of fault ruptures.
7.0 GEOMORPHIC AND EDUCATIONAL SIGNIFICANCE
7.1 The unique geomorphological aspect of Quartz Hill, that has qualified it for entry in The New Zealand Landform Inventory (1990), is its scientific and educational significance.
7.2 It is cited as evidence for the model of landform development (the 'Normal Cycle of Erosion') developed in 1899 by a famous Harvard University professor, William Morris Davis. Sir Charles Cotton was quick to recognise the importance of Quartz Hill and other similar, but less well-developed, landforms in the Wellington region.
7.3 The 'Normal Cycle of Erosion' explains the sequential development of landforms as a mountain range is eroded away. The end point of the model is a 'peneplain'- an erosional surface of low relief developed near sea level.
7.4 W.M. Davis 1895 described the peneplain as 'an almost featureless plain (a peneplain), showing little sympathy with structure, and controlled only by a close approach to baselevel, must characterise the penultimate stage of the uninterrupted cycle'. He viewed the peneplain as the final stage of the fluvial erosion cycle. This concept has a controversial history with more written on it than any other geomorphic idea.
7.5 Many scientists have doubted that it is possible for peneplain to form, because it takes millions of years, and in that time it is expected that the land would be uplifted before it could reach the final form. In fact, no one has convincingly demonstrated that there are any peneplains forming under contemporary conditions at, or near, sea level. Davis' ideas might have been abandoned had it not been for the sort of the evidence so clearly displayed at Quartz Hill.
7.6 Cotton considered that the plateau surface of Quartz Hill, and other similar features in Wellington including Mt Kaukau, represented a peneplain that had once formed at sea-level and had subsequently been uplifted, warped, and eroded.
7.7 Although many workers have recognised the presence of elevated, apparently anomalous, flat areas within the Wellington landscape they do not all agree that these are remnants of a large erosional peneplain. The main concern is that if this surface was formed during the Tertiary Period then subsequent tectonic processes should have affected it. That is, thrust faulting and westward tilting should have deformed the surface. The remnants should therefore be tilted and not level. Cotton noted this difficulty in landscape interpretation. However, he argued that the original, almost horizontal, surface to the west of Wellington had domed upwards along the centre of an anticline rather than tilted. Following uplift, the steeper sides of the anticline (those areas closer to the faults) would erode more rapidly, enhancing the prominence of the uplifted peneplain. Since Quartz Hill is close to the axis of the Wellington Peninsula anticline, and equidistant from surrounding major faults, such a model appears realistic.
7.8 Cotton using the conceptual framework of the erosion cycle, originally treated tectonic influences in the ‘past tense’, as if they were contributing to a static geological structure. The importance of continuing folding and faulting in the evolution of the Wellington landscape is now clearly recognised.
7.9 Early workers, including Cotton, believed that the peneplain was formed near sea level during the end of the Cretaceous and beginning of the Tertiary. Recent workers consider that it is much younger, dating from Pliocene. Research has yet to refine the age of the K-surface, but the best opportunity to do this is at the more extensive K-surface remnants such as Quartz Hill. Whatever its age, Quartz Hill has a special significance in the science of landform evolution.
7.10 Cotton’s recognition of the K-surface as being the base horizon from which to estimate deformation in the region makes this landform of tremendous value to geologists. The surface is assumed to have once been close to horizontal, and net deformation since its development is measured by the deviation of remnants to the surface from that near horizontal plane. While this might not seem a particularly accurate way of estimating deformation, it is by far the most accurate measure that exists over the period of time represented by the K-surface.
7.11 The accessibility and distinctive form of Quartz Hill qualifies it as one of the most important landforms in the Wellington Region.
7.12 For more than 50 years students in first-year geography classes (currently over 200 a year) have been exposed to the significance and relevance of Quartz Hill to the geomorphic evolution of Wellington. Quartz Hill has been the focus for field trip and laboratory exercises aimed at exposing students to the dynamic Wellington landscape. It is used to assist them to develop the skills of enquiry necessary for landscape interpretation.
7.13 This landform, and the landscape of which it forms a part, must be preserved in such away that it can be visited and appreciated by the public, and local and international scholars.
8.0 Why has the 'K-surface' not been protected?
8.1 Given the significance of Quartz Hill and other 'K-surface' remnants to the scientific and educational community the question must be asked as to why they have so far received no protection?
8.2 As already mentioned the unique character of Quartz Hill qualified it for entry in The New Zealand Landform Inventory (1990).
8.3 In 1993 the Geological Society of New Zealand published an inventory of geologically significant sites for the Wellington region. One of the functions of this inventory was to identify and document significant geological sites so that they would not be destroyed by ignorance.
8.4 Quartz Hill was not ranked highly in this inventory, despite its international significance and profile, for two possible reasons.
8.5 First, I believe that the ranking of sites was based, at least in part, on the perceived threat to the feature. At the time Quartz Hill was under low impact pastoral land use and this was most likely seen as the only conceivable use of the area. As a result the character of Quartz Hill was not seen to be at risk. Emphasis was therefore placed on other more immediately threatened sites.
8.6 Second, the inventory had a strong focus on 'geologic' features while much of the unique value of Quartz Hill lies in its geomorphic significance. Had a geomorphologist, or at least someone with a background and training in geomorphology prepared the inventory, I believe the ranking would have been significantly different. The importance of Quartz Hill would then have been recognised.
9.0 The importance of landforms
9.1 Landforms and geological features are important for a number of reasons, including:
9.2 As communities, and individuals, we value the majority of our landscapes very highly. However, to date, there remains with public institutions and territorial authorities a general failure to address landscape and landscape issues as part of the planning and policy framework.
9.3 The courts have found that landscapes are themselves resources, or groups of natural and physical resources, and therefore landscapes are required to be managed sustainably under the RMA.
9.4 Furthermore, under the RMA landscape is understood to encompass the dimensions of the natural and physical environments (ones we are generally able to describe and measure) as well as the 'social, economic, aesthetic and cultural conditions' through which we are conditioned to perceive and experience it. Landscape is not to be regarded as being interchangeable with scenery and views. Specifically, the Fourth Schedule to the Act identifies separately both landscape and visual aspects.
9.5 It has also been ruled that it is the particular values (e.g., natural character) and not simply the resource that is required to be protected. With respect to Quartz Hill this requires that it is the natural character, the largely unmodified nature, and even the bleakness of the landscape that must be protected. It is not adequate to simply recognise the erosional peneplain and then cover it with wind turbines. It is the ‘package’ of landscape characteristics that make Quartz Hill unique. It is this package that must therefore be protected.
9.6 Finally, it might be argued that the geomorphic significance of Quartz Hill is not sufficient to outweigh national benefits for potential power generation, i.e., it is not outstanding enough. However, the courts have ruled that whether a feature is outstanding has to be assessed at the scale of the territorial authorities jurisdiction. There is no doubt that Quartz Hill is outstanding, indeed unique, within the area covered by the Wellington District Plan.
10.0 Conclusions
John McConchie
23 February 2005
