Chapter 2 Desert environments

Abstract

The majority of hazards to construction in desert regions are driven by geomorphological processes at the surface and geological processes within the near-surface. Most of these processes, such as mass movement or fluvial activity, are not unique to deserts and operate in a wide variety of environments. However, as noted in Chapter 1, some, including aeolian erosion and salt weathering, are much more effective or assume a greater relative importance in an arid zone. Geomorphological processes frequently lead to the creation of landforms, many of which are more prevalent in desert environments (e.g. dunes and playa lakes) and pose specific problems for engineering (Fig. 2.1). Fig. 2.1. Diverse desert environments. ( a ) Transverse dunes and mountain ranges in the Atacama Desert, northern Chile (for scale, note figure on dune to top right). ( b ) Ephemeral river channel in mountains SE of Swakopmund, Namib Desert (channel c . 120 m wide). ( c ) Mountain stream entering the northern edge of Chott el Gharsa, west-central Tunisia (channel in foreground c . 80 m wide). ( d ) Linear dunes ( c . 50 m high) on the margins of the southern Rub’ Al Khali, Oman (all photographs © David J. Nash). Climatic conditions in deserts can also pose significant operational difficulties during the construction process. Major problems are caused by the wide diurnal (i.e. daily) temperature fluctuations experienced in most desert regions, and the quality and quantity of water available during construction (cf. Chapter 9). In addition, high rates of water evaporation make the effective curing of concrete difficult. There are contamination issues caused by the deposition of windborne saline dust, and the introduction of chloride and sulphate salts by capillary rise mechanisms. Such conditions may also lead to the rapid deterioration of concrete, and long-term damage to roads and other engineering structures (Cooke et al. 1982; Fookes …