Construction in the Landscape

A Handbook for Civil Engineering to Conserve Global Land Resources

T.G. Carpenter

• Publisher: Routledge
• Year: 2012
• ISBN:
  9781136539565
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Construction & Architectural Engineering
• Index: Technology & Engineering

Construction in the Landscape describes the impact of construction on the land and landscape where it takes place. Geographical coverage is necessarily global to reflect the great variation both in people's economic and social needs and in the shortage or abundance of natural resources.

Part I introduces both land resources, whether used for agriculture, human settlement or mineral extraction or conserved as scenery, wildlife habitat or for the undefined needs of future generations; and construction, its products, skills, processes and impacts on land resources.

Part II describes specific forms of civil engineering - from landform adaptation, through dams and river control works, coastal construction and transport infrastructure to particular types of structure such as bridges, towers and power stations, or the layout of complete settlements.

Part III deals with regional planning of construction and land use in different geographical circumstances - from fine scenery, through rural countryside to city and suburban development - and to the sort of land arrangements that may be sustainable for an increased but hopefully more civilized human population a century hence.

Part I

Land Resources

1

Land Features

1.1 Landscape – an inclusive concept

To most people, landscape is scenery, particularly scenery that they admire and wish to conserve. To some, it also reflects the presence and activities of life forms – from wild nature to cultured humanity – or the opportunities offered by land for production of food, as space to live in or as an amenity for recreation.

The first meaning in dictionaries is indeed scenery – or a painting or other depiction of a view. However, a geographical alternative (in the Shorter Oxford Dictionary, 2007) is a ‘tract or region of land with its characteristic topographical features’, which is perhaps closer to the opportunistic concepts of landscape. Forman and Godron (1986)¹ mention an American (Webster) definition as ‘landforms of a region in aggregate’.

Specific definitions of landscape have been proposed by people with interest in particular land characteristics or uses, for example:

• by painters, guidebooks and those who deplore its depredation: as acknowledged scenery;

• by geographers and landscape designers: as the physiographic and environmental aspects of land (for example, Laurie, 1986);²

• by ecologists: as clusters of ecosystems (Forman and Godron, 1986);³

• by historians: as associations with forests, mountains, rivers or settlements in our individual or collective recollection of past events (Schama, 1995);⁴

• by archaeologists: as surface landforms that recall man’s ancient structural achievements (for example, Muir, 2004).⁵

According to Schama (1995)⁶ the Dutch word landscap once signified a limit of occupation or jurisdiction as much as a depiction of pleasing prospects. In the Netherlands, much of the landscape had already been transformed for productive use; and modern larger scale works have continued its reconstruction to this day.

The Germanic root of the Dutch word is landschaft where the suffix–schaft was equivalent to–ship in English, implying the quality or condition, in this case, of the land. However, by the time the word came to England, first as landskip, in the late 16th century, it meant a ‘picture of inland scenery’ (Jackson, 1986).⁷ Man-made landforms or structures have always been elements of that scenery, much of which was once recorded as background in portrait paintings. Then, as the landscape has become more crowded and land resources in greater demand, people have recognized that there are elements in landscape that are crucial to its conservation but cannot be fully expressed in visual terms. Even in viewed scenery, if there is something that jars our aesthetic sense, then perhaps it is because we sense there is something wrong with treatment of the land itself. Thus a popular concept of landscape today is scenery plus non-visual attributes such as wildlife habitat and cultural association. In this book we regard it as land resources including scenery. Some of the forms of construction addressed in Part II, such as schemes for bulk supply of water for irrigation or the alignment of highways, primarily affect actual land space. Others, such as tower structures or daring bridge crossings, are important elements of scenery.

This chapter introduces basic geologic landforms and the influence of climate and water on them (Section 1.2) and the plant life that clothes the Earth and sustains its animals (1.3). Section 1.4 recognizes the productive and necessary uses of land. The consequent implications for wildlife habitat (1.5) and natural or man-made scenery (1.6) are then discussed as is people’s perception of different aspects of landscape and land use and hence their wish and opportunity to influence plans affecting land resources (1.7).

1.2 Landforms, geology and climate

The forms of the Earth’s surface are consequences of geological processes – orogenic folding, faulting and thrusting, glaciation and wind or water erosion. The most prominent forms are seen where hard rocks have not yet been eroded down to form flatter softer land.

Climate concerns temperature, winds, humidity and precipitation, all with seasonal variations. Temperatures can be too cold to grow crops in the open or to sustain significant populations of people without support from elsewhere; or conditions may be warm and moist enough to promote luxuriant vegetation and abundant animal life – but also virulent pests and diseases.

Winds bring humid air and water vapour in wet zones, or scorching erosion to arid lands. Precipitation, as seasonal rainfall, falls directly on forest, grassland or cropland, providing opportunity to manage vegetation as crops for people or fodder for animals. Or the rain runs off or the snow melts, feeding streams and rivers or seeping into the ground.

Low temperatures and ice or water cause glacial movement in the high mountains, permafrost in flatter northern lands, and rough terrain with poor soils and irregular drainage in both conditions. High temperatures or diurnal extremes of freezing and thawing can shatter outcropping rock. Where rainstorms are occasional but intense, surface run-off may carry off topsoil. Streams in flood erode their banks or undermine sloping ground. The resulting eroded material – sediment – is transported downstream and deposited as alluvium in less steep territory.

Four representative types of physical geography represent typical landforms in a sequence from hard and chaotic rock geology down to soft plains and deltas.

Mountains, gorges and escarpments, together with their lakes and cataracts, are grand scenery. With the exception of certain settlements or storage reservoirs in the valleys, they are best left as such, being less suited to productive land use.

Gently undulating hills are more evenly eroded and rounded, for example in the ranges of the Appalachian Mountains or the less steep regions of Mediterranean Europe. Natural rock outcrops are scarce and, in humid regions, smooth-sided valleys divide often wood-clad uplands of roughly equal altitude. With adequate soil and in suitable climates, these hills may offer slopes, terraces and plateaux suitable for agriculture, grazing land and forestry.

Alluvial plains comprise eroded sediment deposited during past and contemporary floods so that the land is now generally flat. Often the soil is richly fertile, sometimes so uneven as to be suitable only for grazing or so saline that few species can grow. Seasonally flooded land may be better suited to pasture and flood recession agriculture than to permanent settlement; but engineering structures and embankments can do much to influence the flow of flood water over the land or to protect habitation.

Deltas are formed by the deposition of sediment where rivers debouch into the sea, lakes or reservoirs. Their formation is a continuous process as long as the flow pattern of the river is unaltered by constructing dams and control works. The build-up of the delta of the River Nile into the Mediterranean Sea was reduced or reversed in the 1930s and 1940s; one of the causes was construction of barrages in the delta and of dams on the main river further upstream. The delta may have started to advance again from 1954 but its retreat recommenced rapidly after completion in 1970 of the Aswan High Dam prevented any more sediment passing downstream. The Akosombo Dam in Ghana has had a similar effect at the Atlantic outfall of the Volta River.

Other deltas, like that of the Mississippi and the Po rivers continue to advance and the consequences in protecting cities such as New Orleans or Venice are fraught with problems requiring expensive engineering solutions.

1.3 Life forms – animals and vegetation

Living organisms are:

• animals that have sense organs and nervous systems but can survive only by eating organic food, such as vegetation or other animals;

• vegetation, inanimate plants which absorb water and inorganic substances through their roots and synthesize nutrients in their leaves;

• microorganisms, which may fall into either category, are too small to be normally noticeable but are hugely abundant in all animals and plants and critical in the way in which all these life forms interact.

Ecology is the scientific study of relationships between organisms and their physical surroundings (habitat). Flora and fauna interact with other species in complex communities (ecosystems).

Animals fall into four categories as far as land use is concerned:

1 Human beings, who dominate all but the most remote places.

2 Domesticated farm livestock, such as cattle, sheep, goats, pigs or fowl, which require pasture and, sometimes seasonally, extra fodder or weatherproof accommodation.

3 Small domestic, feral or wild mammals that live in human environments such as villages and suburbs.

4 Wild creatures who live entirely naturally and whose survival depends on continuance of their habitat.

Vegetation can be similarly represented by three very broad classes in a world dominated by people:

1 Crops in cultivated fields, orchards and plantations; or commercial forests.

2 Incidental trees, offering shade and green attraction in human settlements, or gardens or lawns managed for amenity and recreation.

3 The plants and trees of wild land – from isolated wilderness on rough slopes or small wetlands to extensive tropical forest – that provide a habitat for wild animals.

Agriculture and forestry are mentioned here because they cover so much space and to observe that certain crops or trees suit certain land resources. Trees as a human amenity are features of settlement, wild animals of nature conservation.

Agriculture is the science or practice of growing food and industrial crops. It uses seeds, plants or livestock that have been selected, bred or modified to yield optimum types and amounts of produce. Types of agriculture can be related to the climate, soil fertility, topography (surface contours) of the land and the way in which the crops are watered. Cold climates favour only those hardy plants that can withstand frost or can grow during a comparatively short warmer season. Dry climates, even where the soils are fertile, cannot be agriculturally productive unless extra water is provided. Temperate climates with timely rainfall are ideal for many agricultural crops. Wet tropical climates engender profuse growth both welcome and destructive.

Soil fertility relates to its grading, chemical composition and nutrients as well as drainage conditions and the thickness of organic topsoil. Fertility can be exhausted by intensive cropping; or it can be restored – artificially by adding chemical fertilizers or organic material, naturally by rotating the primary crops with years of fallow or special plants such as nitrogen-fixing legumes.

In luxuriant growth such as tropical rainforests, the trees and undergrowth are sustained almost entirely by sunlight, rainfall and nutrients recycled through the vegetation itself and not through the soil. The latter is therefore bereft of the sort of nutrients and perhaps water retention or drainage needed for cultivation of ground crops. As a consequence, agriculture on land cleared from tropical jungle tends to fail because:

• the soil is unsuitable due to these deficiencies;

• growth of weeds and soon secondary forest requires arduous effort to combat; and

• pests and diseases are difficult to overcome.

Fortunately rice, the staple food for half of humanity, can overcome much of the tropical soil problems. Paddy rice grows in shallow water, thrives in a warm humid climate and forms an impermeable pan that eludes the loss of water by downward seepage (Young, 1998).⁸

Steep land is difficult to cultivate or harvest mechanically; and it may have to be terraced to retain water. But very flat land may be difficult to drain and can become waterlogged. Crop watering can be entirely by rainfall in wet climates; or water may have to be collected, stored and applied by an irrigation system in drier conditions.

In the past, seeds for agriculture have been selected, hybridized or genetically modified, primarily to raise the yield of crops. These yields are difficult to maintain without considerable inputs of fertil...

Table of contents

• Cover
• Halftitle
• Title
• Copyright
• Contents
• List of Photographs, Figures and Tables
• Preface
• List of Acronyms and Abbreviations
• PART I. Land Resources
• PART II. Man-made Forms and Structures
• PART III. Planning Construction in Various Landscapes
• Subject Index
• Index of Places, Projects and People