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.