Abstract

A laboratory study was used to determine the form of the relationship between the suspended sediment concentration (SSC) and the spectral reflectance (R). It was hypothesized that when the SSC was high the relationship would be log-linear at short, visible wavelengths (where only a small portion of the radiation would be absorbed by water and the reflectance asymptote would be reached at low levels of SSC) and linear at long, near-infrared wavelengths (where a large portion of the radiation would be absorbed by water and the reflectance asymptote would be reached at high levels of SSC). The data comprised spectral reflectance recorded in 875 wavebands from 350 to 2500 nm for eighteen sediment type/grain size samples, each at up to thirty SSC concentrations over a range of 0 to 1300 mg I-1. The strong relationship between SSC and R was, as hypothesized, log-linear for wavelengths from 450 to 700 nm and linear from 700 to 1050 nm. The applicability of this information was illustrated in relation to the collection of data by the Daedalus 1268 multispectral scanner. It was recommended that in situations where a limited number of SSC measurements is available for the calibration of the SSC/R relationship, a log-linear relationship be assumed for wavebands 1 to 5 and a linear relationship for wavebands 6 to 8.