Abstract:
Considering the current lack of engineering geological mapping in urban developments
in Namibia, it was necessary to pioneer the input of engineering geology in the planning
of infrastructure. The benefits of engineering geological mapping in sustainable
development were highlighted and present methodologies were explored, looking at
their applicability to Namibia. The early activities of engineering geological mapping
include terrain classification, which groups areas of terrain that have similar conditions.
It applies the principle of homogeneity such that areas falling under one terrain class are
treated the same during planning, as they are deemed to have the same impact on
engineering structures. The traditional way of doing terrain classification places much
reliance on topography features, such as valleys, streams, etc. However, this becomes
fairly difficult to apply in flat lying areas where topographical features may not be
readily visible from aerial photographs. Therefore, soil variability mapping using colour
and texture, vegetation mapping, and damage distribution mapping or structural damage
techniques were recommended to aid terrain classification in flat lying semi-arid
environments. Employing these techniques, Outapi Town in northern Namibia was
mapped, identifying four terrain classes. With subsequent testing methods, these were
upgraded to just three engineering geological zones. The main geotechnical constraints
identified include the possibility of collapse settlement given the aeolian nature of the
Outapi soils, susceptibility to flooding attributed to the flat nature of the area with no
properly defined pathways, potential for dispersion as the soils are rather fine and saline,
and, to a lesser extent, the presence of potentially expansive soils.
