Engineering Geology

Chapter 8
Movement of sand can bury obstacles in its path such as roads and railways or accumulate
against large structures. Such moving sand necessitates continuous and often costly
maintenance activities. Indeed, areas may be abandoned as a result of sand encroachment
(Fig. 8.18). Stipho (1992) pointed out that only a few centimetres of sand on a road surface
can constitute a major driving hazard. Deep burial of pipelines by sand makes their inspection
and maintenance difficult, and unsupported pipes on active dunes can be left high above the
ground as dunes move on, causing the pipes to move and possibly fracture.
Aerial photographs and remote sensing imagery of the same area and taken at successive
time intervals can be used to study dune movement, rate of land degradation and erodibility
of surfaces (Jones et al., 1986). The recognition of these various features by the use of
aerial photographs should be checked in the field. Field mapping involves the identification
of erosional and depositional evidence of sediment movement, which can provide
useful information on the direction of sand movement but less on dust transport.
For instance, indirect evidence of the wind regime can be derived from trends of active
dunes. As their destabilization by human activity should be avoided, it is important that
dunes be identified and monitored.
Figure 8.18
Orchard partially buried by moving sand, Hebei, Gu’an County, China.
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