Towards a new method for shallow-water monitoring using remote sensing

The influence of the optical depth and the bottom depth and albedo on radiances leaving turbid shallow-waters is investigated. A simplified shallow-water reflectance model (SWRM) is tested. Simulations are performed in order to determine accurate solutions of the radiative transfer for various types of turbid shallow-water. Characteristical values of diffuse attenuation and water reflectance are computed. The latter feeds the SWRM and an effective diffuse attenuation coefficient is derived, which is compared with the exact one. Since the ratio of the diffuse attenuation coefficient for light travelling upward to the diffuse attenuation coefficient for downwelling irradiance is governed by the relative importance of scattering upon absorption, the effective diffuse attenuation coefficient is found to be highly dependent upon the nature of the water column content such as suspended particles and yellow substances. Thus, a set of characteristical values of the model parameters must be defined for typical shallow water environments, in order to preserve a sufficient accuracy in the determination of water-leaving radiance. We take advantage of both in situ measurements and simulation results to fulfill that objective.