Geophysical surveys involving the techniques of electrical resistivity imaging, electrical sounding and
magnetics were employed to characterize the ground conditions at a proposed dam site at Hizaeti-Afras,
Wukro, North Ethiopia. The techniques were utilized to map the depth to the competent formations, their
relative suitability for foundation work and the presence and extent of weak zones in the subsurface. The
work has mapped the different lithologic units of the subsurface and determined the depth to the basement
rocks in the area. Through correlation of the inverse model resistivity sections of the imaging surveys,
the geoelectric section of the sounding survey and the magnetic profile plots with available
borehole lithologic logs, it is shown that the results very well supplement the geotechnical point data
in addition to providing a wider coverage in mapping areas of weak ground that could otherwise be
missed with widely spaced borehole information. The combined results of the survey show the proposed
dam axis to be unsuitable. The power of the electrical resistivity imaging technique and its potential to
map the shallow subsurface with adequate resolution are illustrated. The result is a strong suggestion
that geophysical techniques can be used to assist and extrapolate borehole geotechnical data especially
when large area is to be used for development of large infrastructure.