Geophysical Approach for Water Seepage Study in Near Surface Assessment

Abstract

Water seepage at urban area will affect the hydraulic
conductivity and shear strength of soil that may cause
subsurface problems such as landslides, sinkholes, cavities,
ground subsidence and hazard to buildings. To delineate
seepage pathways, geophysical data will be acquired. A study
has been conducted at Penang to study the saturated zone,
analyze the water flow directions and intensities to determine
the causes of localized near surface problems by using the 2-D
resistivity and self-potential (SP) methods. Five 2-D resistivity
survey lines with minimum of 0.5 m electrode spacing were
executed using Pole-dipole array. The flow directions and
intensities of the water were determined using self-potential
(SP) method with interval spacing of 1 m. The inversion results
show the low resistivity value (1-100 Ωm) was dominant at the
study area which was interpret as saturated zone. Resistivity
value of 100-800 Ωm was interpret as alluvium. The result
display by self-potential contour map shows the water flow from
higher self-potential value (38 mV) towards the lower selfpotential
value (-22 mV) that is flow from west to east, which are
related to seepage flow patterns, negative SP anomalies were
related with subsurface seepage flow paths (recharge zone) and
positive SP anomalies were related with areas of seepage
outflow (discharge zone). Therefore, the two results have match
and show good correlation in water seepage investigation,
which validates the results