FINAL REPORT: Optics, Acoustics, and Stress in a Nearshore Bottom Nepheloid Layer

The approach was to obtain measurements that permitted comparisons of temporal evolution of bottom stress, suspended particle size, and optical and acoustical properties in the bottom boundary layer. The instrumentation was mounted on bottom tripods and an I-beam frame. The "OASIS" tripod included a 9-wavelength optical attenuation and absorption meter (WetLabs ac-9, with automated dissolved measurement for calibration-independent particulate measurements), LISST-100 (Type B) and LISSTFloc laser diffraction particle sizers (Agrawal & Pottsmith 2000), a digital floe camera (DFC) (Curran et al. 2002), a Tracor Acoustic Profiling System (TAPS), and an array of SonTek/YSI acoustic Doppler velocimeters (ADVs). Near-simultaneous ac-9 measurements with and without a filter assured highquality particulate spectral absorption and attenuation measurements. The LISSTs and DFC together provided particle size distributions from 1.25 urn to 1 cm in diameter. The TAPS and ADVs obtained acoustical backscatter intensity over a wide range of frequencies that were used to generate particle size distributions (Holliday, 1987; Hay and Sheng, 1992). In 2006-2007 a new tripod was constructed and deployed. It is called the Modified In Situ Size and Settling Column Tripod (MINSSECT). It was developed to provide better constraint on conversions between optical signals, particle area, and particle mass. It carries a digital floe camera, a LISST-100 (Type B), a video settling column, and an