Mapping small-scale along-front structure using ADCP acoustic backscatter range-bin data

A quasi-three-dimensional view of a scallop-shaped river plume front is derived using acoustic Doppler current profiler (ADCP) backscatter measurements recorded in individual range bins. The data show that the scallops consist of broad troughs of plume water separated by narrow cusps of ambient water and have an along-front wavelength of about 13 m. Having this view across such an inhomogeneous region is helpful in interpreting the corresponding ADCP velocity measurements, so that an examination of just those ADCP profiles made in the ambient water shows the expected strong sinking motion, which reaches about 25 cm s−1 at 1–2-m depth.