Effects of bottom type variability on modeled backscattered levels of a high-frequency sonar

Abstract

Results investigating the effects of variable bottom composition on modeled high-frequency backscattered levels are presented for a typical shallow water, range-dependent environment. The modeled environment consisted of a single sound-speed profile, a flat sea bottom with range-dependent bottom composition, and a benign sea surface. Coarse and fine grain sandy areas were partitioned in range to create range dependence. Bottom backscattering and reflection loss for each partition were obtained from the recent University of Texas high-frequency ocean bottom backscatter model [N. P. Chotiros and F. A. Boyle, 3264(A) (1994)]. Differences of 5 dB were discernible between the fine–coarse–fine sand bottom and a range-independent fine sand bottom for ranges <500 m. The trend and structure of the backscattered levels were nearly identical for both bottom types. Differences of 42 dB for ranges <500 m were visible in the modeled backscattered level of the fine–coarse–fine sand bottom and the coarse–fine–coarse sand bottom. The trend and structure of the backscattered levels were also different. In all cases, surface reverberation had a strong impact on the backscattered levels, trends, and structures. [Work supported by MCM Tactical Environmental Data Systems (MTEDS) under Program Element 62435N.]