The present work is a geophysical study of a riverbank exposed to erosion and it aims to evaluate
its use for detecting areas degraded by critical erosion stage before they collapse. The
studied area is situated 600m alongside Guamá River – between Tucunduba River Bridge and
Canoeing Pier at Federal University of Pará. The area has different kinds of erosion contentions
along its way such as cement walls and cement bags. Therefore the place is considered a
laboratory to test geophysics expertise in detecting areas affected by imperceptible process so
that it can act before they erode. The following four geophysical methods were used: spontaneous
potential –SP; electroresistivity; Slingram – LIN and ground penetration radar – GPR.
The measures were taken during both low and high tides in order to map the preferable subsuperficial
paths the water runs through. In general, tides increase oscillations in SP measures,
electroresistivity and LIN as well as increase the reflections intensity from GPR compared to
low tide measures and during high tide, measures show compared to low tide: I) In erosion
affected area there is a voltage decrease in SP, a resistivity decrease in electroresistivity, a
conductive increase in LIN as well as an intensity increase of the reflections and a continuity
disturbance in GPR. II) In contained areas there is an increase of the SP voltage, an increase
of the resistivity from electroresistivity, a decrease of the LIN conductivity and an ease in the
reflections from the GPR and a reduction of tides global effects. Despite the difficulties, the
results show Geophysics can be a useful tool not only on preventing affected areas from collapsing
but also on analyzing the effectiveness of previous contention woks.
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