Desk study, remote sensing, geographical information systems and field evaluation

In science and engineering, including engineering geology and geotechnical engineering, initial investigations can be particularly cost-effective for early evaluation and the planning of subsequent investigations: ‘time spent in reconnaissance is seldom wasted’ (purportedly said by Napoleon Bonaparte). But the work needs to be well planned and executed if its findings are to be used properly and their potential benefits are to be realized. Clients and their professional advisors are frequently exhorted to carry out desk studies and other investigations early in the design of a project (e.g. among many publications: Association of Geotechnical and Geoenvironmental Specialists 2006; BS EN 1997-2). Unfortunately, such advice is sometimes ignored. This chapter contains advice on desk studies and field evaluation for projects in hot deserts. Much of the advice also applies to other geographical and geological environments. However, some is specific to hot deserts, and it is this advice that is emphasized. Hot deserts are defined by their climate. In addition to their aridity, high temperature and large daily range in temperature, four other attributes make deserts distinctively challenging for engineering projects. Wind – the effects of wind on the bare desert surface; the movement of sand and dust. Groundwater – the general absence of groundwater at shallow depths. Surface water – the erosive and inundating effects of storms: flash flooding in wadis and sheet flooding on the desert surface. Chemistry – desert temperatures and aridity result in the development of minerals and materials that are not present (or are much less familiar) in other climatic zones. Examples are the presence of gypsum, and the formation of crusts and cretes at or a little below the ground surface. In this chapter, consideration is given to work carried out prior to intrusive ground investigations and geophysical surveys, which are described in Chapter 7. Indeed, …