J. C. Doornkamp

Large scale geomorphological mapping and Highway engineering design

Summary Geomorphological mapping in site investigations for highway engineering is proving to be a rapid means of obtaining much relevant information about ground conditions. Such mapping requires the recognition of both the origin of surface features and the geological processes that still influence them. In addition information about materials is recorded and inferences made about their extent. The paper identifies eight aims of a geomorphological survey for highway engineering and discusses these in the context of small-scale maps and large-scale plans. The latter are illustrated by case studies from Nepal and South Wales. The review identifies the established applications of geomorphological mapping to site investigation and concludes that further work can usefully be directed towards a broadening of the geomorphological content of site investigation.

Rapid geomorphological assessments for engineering

Summary Geomorphological mapping is being used increasingly in engineering projects (especially at the reconnaissance and site-investigation stages) as a rapid, highly cost-effective means of assessing both potential hazards and resources. This is normally achieved through a field mapping programme which is dependent on the availability of aerial photographs, and which involves the correct interpretation of landforms as to their origins, material composition, and associated present-day geomorphological processes. The results of such a survey need to be presented in a form which is of direct use to an engineering geologist and/or engineer. This is best achieved, in most cases, by the production of problem or site-orientated maps derived from the primary geomorphological survey. The case studies, drawn from several investigations in arid land environments, were made by a small team of (3-5) geomorphologists and geologists, working for short but concentrated periods of time in the field. A search for fine aggregates in Bahrain was closely associated with the identification and mapping of contributing drainage networks and source areas for alluvial fan deposits. Thelocation of trial pits and boreholes at a site in Dubai was rationalised in terms of a reconnaissance map of both landforms and their constituent materials; while at Suez, extrapolation between existing trial pit and borehole sites was made possible from the geomorphological mapping of landform boundaries. Hazards to engineering from flooding (at Suez) and dune migration (in Dubai) were identified, assessed, and mapped on the basis of a knowledge of their place in the overall geomorphological system.

Clay shrinkage induced subsidence

Droughts since 1971 have been responsible for foundation problems associated with clay soils. The effect has been to face insurance companies with claims running into millions of pounds. Although methods exist for defining the relative risk of such damage from one part of Britain to another, based on an analysis of the location of clay soils, there is a likelihood that the climatic changes predicted will cause an increase in the frequency of damaging drought events. Insurers will need to take this into account when assessing their needs in terms of reserves required to meet future claims.

Middle East—Review and Bibliography of Geomorphological Contributions

It is the purpose of this brief review to provide the engineer with some background information and bibliographic sources to geomorphological studies relating to arid areas, especially the Middle East. Table 1 summarises some aspects of engineering work in deserts in which geomorphological studies have a role to play, especially with respect to resource appraisals and to the environmental hazards in arid and semi-arid areas. The analysis of aerial photographs and field survey to map features and deposits of engineering significance can be carried out on a variety of scales (see below). Landforms can be used as indicators of other environmental phenomena of importance to engineering (see Fookes, this vol.). Hazard maps including maps of flooding, unstable sand dunes and salt-weathering processes are frequently produced, and hence the geomorphologist can also help to establish the ways in which undesirable hazards and environmental processes can be ameliorated. Tricart & Cailleux (1969) and Cooke & Warren (1973) give general treatments of desert landforms and processes and provide extensive multilingual bibliographies. Two important bibliographies are those by Lustig (1968) and by Perrin & Mitchell (1969). Many of the modern techniques of quantitative geomorphological analysis and monitoring that have been applied to deserts have been brought together by Schick, Yaalon & Yair (1974), while desert sediments and sedimentary structures of ephemeral streams have been investigated by Glennie (1970) and Picard & High (1973) respectively. Bagnold’s classic work on wind processes remains an essential introduction to aeolian geomorphology (Bagnold 1941). Certain specific desert features have

Environmental geology mapping: An international review

Abstract Interest in environmental geological maps (EGMs) has increased in Britain since the publication in 1982 of the IGS Report 82/15 Environmental Geology of the Glenrothes District, Fife Region. Over the past decade or so similar interests have been developing elsewhere, particularly in the USA and in Europe. This review examines the style and purpose of EGMs in both the USA and Europe, and recognises distinct, yet different, characteristics in each. The review provides a reference against which British experience, when it is published, can be assessed. The US work, though very variable in style and scale of mapping, is consistently concerned to provide earth- science information to planners, engineers and politicians concerned with development, urban growth and redevelopment. The weakest of these studies provide raw geological data, the best make an effort to translate these data into terms that can be understood by the potential user. The European approach to EGMs has been different in that it tends to appear under the title ‘engineering geological maps’, and in some cases, such as under the ZERMOS scheme in France, has a direct relevance to the concept of Le Code de L’Urbanisme et de l’habitation (article R 128.18, 1970). In fact variations in style and purpose exist across Europe, with varying degrees of influence upon regulations or legislation in terms of planning and development.

Analysis of the Surface Texture of Selected Quartz Grains From Southern Africa Using a Scanning Electron Microscope

Abstract The use of the scanning electron microscope (SEM) in, the analysis of soils and sediments is described. Particular reference is made to some applications within Southern Africa that suggest (i) the presence of fluvial deposits above the Zambezi gorge below the Victoria Falls. (ii) widespread silica precipitation as plates. resulting from present-day soil-water conditions. especially in the Matopos HiI1s of Rhodesia. (iii) a change in soil-water conditions. and possibly climate in the northern Transvaal near Louis Trichardt. and (iv) the efficacy of semiarid and desert weathering conditions in the southern Kalahari area near Uppington.