Influence of bottom depths and bottom types on water surface reflectance

Abstract

Two flow irradiance model solutions are tested using various bottom depths and hyperspectral in-situ bottom reflectance signatures for Elkhorn Coral, Bleached Reef, Sand, Sand and Seagrass, and Turtle Grass. Bottom reflectance signatures are used to simulate a water surface reflectance signatures from analytical solutions that can account for the effect of a collimated irradiance signal or direct sunlight within the water column. Simulated reflectance signatures are generated as a function of depth and wavelength in an optically clear water column and a turbid estuarine water column containing concentrations of chlorophyll-a, seston, and dissolved organic material. Simulated surface reflectance signatures as a function of water depth are then used to predict bottom reflectance signatures. Comparison of in-situ bottom reflectance signatures to simulated bottom reflectance signatures predicts model depth sensitivity at a 95% confidence level. Spectral window solutions for water column depths are detected for bottom types and estuarine type water column concentrations. Model can be coupled with bathymetry and high resolution water surface sensor derived reflectance signatures to monitor or map bottom variations for surveillance, environmental monitoring, fishing, or dredging applications in coastal waters or very shallow estuarine waters.