A buried river channel in an intertidal area at Barry Old Harbour, South Wales, UK, is investigated using high-resolution seismic refraction and reflection techniques. The refraction technique is able to profile the base of the 20m deep buried valley because the Carboniferous Limestone bedrock has a significant velocity contrast with overlying water-saturated unconsolidated sediments.
Common midpoint (CMP) reflection profiling, using a single detonator as the seismic source, images the base of the river channel and the internal sedimentary sequences. Seismic reflections with frequencies in the 400 to 600 Hz range are observed from as shallow as 5 m depth (6 ms two-way time).
The bedrock profiles derived from the refraction and reflection experiments are in precise agreement.