Terrain Evaluation

Colin W. Mitchell

• Publisher: Routledge
• Year: 2014
• ISBN:
  9781317885221
• Edition: 2
• Topic: Physical Sciences
• Subtopic: Geology & Earth Sciences

Written from the point of view of the earth scientist, this book acts as an introduction to terrain evaluation. The emphasis throughout is on the physical rather than the economic, social or legal aspects of the subject, and topics covered include remote sensing and data processing technologies.

Part I

Principles of terrain evaluation

1

What is terrain Evaluation?

1.1 Outline and objectives of this book

Terrestrial life depends on a surface mantle of rock and soil not more than a few metres deep and the associated plant cover. The character and behaviour of this mantle under the influence of climate determine its suitability for all types of land use. Terrain represents one of the triad of factors of production: land, labour, and capital. It differs from the others in being relatively fixed in location and extent and in being more amenable to geographical forms of analysis. Accelerating population growth and earth-transforming technologies are changing the environment at an unprecedented rate, often for the worse. At the same time, modem methods of data processing make it possible to gather and manage information much more efficiently and rapidly than hitherto. There is an urgent need to harness this capability in order to improve land use and management.

Terrain evaluation is an important technique in achieving this. It integrates other land resource factors, notably surface materials, soils, water, and vegetation on a common readily comprehensible basis, such that a map of terrain can be used as a framework for the others. For this reason, it forms the basis for the interdisciplinary approach known as ‘integrated survey’.

Part I of this book considers the general principles of how and why an intelligence system based on terrain forms a valuable foundation for land use planning. The latter part of the present chapter defines terms, gives an account of the scope and requirements of an environmental intelligence system, and outlines the reasons for using a natural classification of terrain as its basis. Chapter 2 discusses the scale spectrum, the conceptual development of regionalizations, and boundary delimitation, and Chapter 3 outlines terrain and landscape classifications from international to local scale. Chapter 4 describes the way in which these have been developed into parametric and physiographic schemes, and Chapter 5 outlines a scalar hierarchy of physiographic units.

Part II outlines the type of information about the earth’s surface required in a practical intelligence system. Chapter 6 considers the variations imposed by climate, structure, and Ethology on surface form, and Chapter 7 the natural processes causing erosion, degradation, and pollution of the environment. Chapter 8 discusses the place of vegetation both as an aid in the recognition of terrain units, and in schemes where it plays a part in defining them, and considers the relevance of different types of vegetation classification to terrain evaluation.

Part III (Chs 9–15) deals with the practical aspects of data collection and analysis. This includes the techniques of project planning (Ch. 9), remote sensing (Chs 10 and 11), sampling (Ch. 12), field observation (Ch. 13), geographical information systems and data processing (Chs 14 and 15). Since these techniques have wide applications in all environmental sciences, the emphasis is on aspects specifically relating to terrain surveys, giving literature references to enable the reader to follow up specialist aspects in detail.

Part IV covers the techniques of display, reporting, and mapping of terrain data, Chapter 16 giving the principles of terrain mapping, and Chapter 17 showing how this and other forms of data presentation can be developed as an output from a geographical information system.

Part V (Chs 18–27) describes the applications of terrain evaluation to each of the main practical disciplines concerned with land uses. These are: environmental climatology, hydrology, geology, soils, archaeology, agriculture, civil and military engineering, and environmental planning. The general format of each chapter is first to discuss the relevance of terrain to the land use in question and then to describe the systems which have been developed for analysing and classifying the terrain for it. The final chapter synthesizes these methods and systems in relation to likely developments in the 1990s.

1.2 Definition of terms

The term ‘terrain evaluation’, used as the title of this book, follows the precedent of research carried out under the auspices of the Military Engineering Experimental Establishment (now the Military Vehicles and Engineering Establishment) (Beckett and Webster, 1969). The subject has developed in response to the need for an understanding of terrain by the increasing number of disciplines concerned with its use. These are both the pure sciences, such as geology, hydrology, geography, botany, zoology, ecology, pedology, and meteorology; and the applied sciences, such as agriculture, forestry, civil and military engineering, and landscape planning. This range of interest underlines the need for explaining terminology which may be understood in different senses in different disciplines.

‘Terrain’ is defined by the New English Dictionary as a ‘tract of country considered with regard to its natural features and configuration’. This is preferable to similar terms because its meaning is more strictly confined to the surface of the earth and has fewer academic and practical connotations. It has now been used in the tides of a number of publications in this sense, e.g. Beckett and Webster (1969), Way (1973), and Townshend (1931). ‘Environment’ and ‘milieu’ have meanings which are somewhat too general and extend well beyond the confines of geography. ‘Physiography’ is an older term which includes not only surface form and geology but also climatology, meteorology, oceanography, and natural phenomena in general. ‘Geomorphology’ has the advantage of being more narrowly confined to landforms but is too strongly involved with considerations of process. ‘Microrelief’ is too exclusively geometric and does not comprehend earth materials or structure. ‘Regolith’ and ‘soil’, conversely, relate only to materials and not to geometry, regolith being restricted to the loose overburden mantling undecomposed bedrock and soil still more narrowly limited to its upper and biophysically weathered part. ‘Landscape’ or ‘land’ are perhaps the closest equivalents, but both are somewhat wider concepts than terrain. The former rather too strongly connotes the visual and artistic aspects, and the latter has been given the specific technical meaning of the total physical environment (including climate, relief, soils, hydrology, and vegetation) to the extent that it influences land use (FAO, 1976a). Terrain must also be distinguished from the term ‘terrane’ used by geologists for three-dimensional blocks of crust characteristically separated from each other by tectonic action. These may be large such as the Guyana and Saharan Shields separated by the Atlantic Rift, or smaller fragments of crust in younger mountain ranges such as the North American Cordillera.

‘Evaluation’ is defined as the ‘act or result of expressing the numerical value of; judging concerning the worth of’ an object. This double meaning makes it somewhat more inclusive and thus preferable to such terms as ‘analysis’, ‘quantification’, ‘assessment’, or ‘appraisal’.

1.3 The scope of terrain evaluation

The scope of the subject is wide. It begins with the user’s need and the whole problem of acquiring information about the terrain both from old records and new field surveys, laboratory studies, and statistical analyses. It therefore includes the study of these techniques. Secondly, it is concerned with the abstraction, classification, storage, and reproduction of such information to make it available quickly and cheaply to users. Thirdly, it considers the means by which these ends can be achieved.

Land is not static but experiences continual change both of its physical characteristics and also of the socio-economic conditions governing its use. The absolute and relative values placed on different tracts vary between societies and over time in the same society. Many examples of this could be quoted. The sugar-growing islands in the West Indies were highly valued in the eighteenth century but became much less important after sugar-beet became the main source of sugar in Europe as a result of the British blockade during the Napoleonic Wars. Similarly, the changed patterns of leisure in the last generation have dramatically increased land values in popular recreational areas such as the Alps, Mediterranean, Caribbean, and east Australian coast. There is now great pressure on land and ecosystems in specially favoured and accessible locations such as the shores of Lake Geneva, the Costa do Sul, southern Florida, and the Great Barrier Reef islands.

Even in the same society, land evaluations must take account of different perceptions of the environment, especially concerning rural areas. These perceptions have been altered and sharpened in recent years by the wider appreciation of the fragility of our planetary ecosystem and of the need for conservation. We can discern two types of approach today. The first, which could be called the ‘environmental management approach’, sees the existing pattern of land use as being in approximate equilibrium with the environment. It favours leaving the existing system approximately as it is and altering it only to maximize production and minimize wastage. The second, or ‘socio-economic planning approach’, seeks all-round improvement by replacing the old ecosystem with a planned new one. The difference between these two approaches is more than academic because we are already faced in some areas with pressures to manipulate land resources in ways which cannot be harmonized with maintaining their short-term equilibrium.

There are three types of terrestrial phenomenon which are generally excluded from consideration in this book as they do not fall within the normal definition of terrain:

1. The atmosphere. This is too variable and ephemeral to be assigned to sufficiently small and closely definable tracts of the earth’s surface.

2. Large expanses of water beyond the range of riparian uses. These are subject to different types of analysis than are applicable to terrain.

3. That part of the earth’s crust which lies at a greater depth than about 6 m. Terrain evaluation is not concerned with operations such as mining and well drilling except in so far as they involve the exploitation of the immediate surface.

1.4 Information requirements of a terrain evaluation system

Although a wide range of professions is concerned with land uses and the aggregate of their information requirements is large, it is not infinite. There is considerable overlap between the interests of different users. Most would agree on a central core of important information about land which would include such properties as gradient, soil texture, and moisture regime. Each would, however, require additional data of less general interest. Only agriculturists and foresters, for instance, would need detailed information on soil nutrient status, and only engineers would require it on some aspects of soil strength.

Nor is the range of land use intensities infinite. Terrain must always be evaluated within an economic context, and the importance of biophysical factors relative to others diminishes at very large and very small scales. Planning at international or national levels is concerned with macro-economic considerations of which terrain forms only a small part. At the other extreme, the construction of buildings or monuments or the layout of gardens involve s...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Dedication
• Table of Contents
• Preface
• Acknowledgements
• Part I. Principles of terrain evaluation
• Part II Terrain data requirements
• Part III Collection and analysis of terrain data
• Part IV Display, reporting, and mapping of terrain data
• Part V Applications of terrain evaluation
• Bibliography
• Appendix A Example of a method of sampling the terrain of a large area: the hot deserts of the world
• Appendix B Field measurements of hydraulic conductivity and infiltration rate
• References
• Index