Characterization of seafloor roughness from high-frequency acoustic backscattering measurements in shallow water off the west coast of India.

Abstract

Measurements of the reverberation time series are made at frequencies of 8, 10, and 12 kHz, and the corresponding acoustic bottom backscattering strengths are estimated as functions of grazing angle. The experiment was conducted in the western continental shelf of India (off Kerala) in water depth of ∼61 m where hard sandy sediments of biogenic origin are predominant. The average values of two-dimensional (2D) spectral strength (w2) and exponent (γ2) of seafloor roughness are obtained by inverting bottom backscattering strength data with the help of a scattering model, utilizing the genetic algorithm method. Measurements of one-dimensional interface roughness height are also carried out using a single beam echosounder to analyze the variability of bottom roughness in terms of spatial frequency. The spectral parameters estimated from roughness height measurements are compared to that obtained from inversion results. The 2D spectral strength and exponent of seafloor roughness estimated from the two methods agree with each other and are consistent with the typical values associated with sandy sediments.