A new method for estimating suspended sediment concentrations and deposition rates from satellite imagery based on the physics of plumes

Sediment plumes are typically easy to identify in satellite imagery and there is a great interest in being able to measure suspended sediment concentrations (SSC) from space or airborne instruments. The standard approach to this problem to date has been to try to determine the spectral signatures of different suspended particle mixtures, either empirically or theoretically, and to thereby develop transfer functions that convert multi-band reflectances to SSC. Although this approach has met with some success, there is not yet a robust and accurate algorithm to quantify SSC in plumes in the nearshore environment under varying conditions. This paper describes a completely different and therefore complementary approach to this problem that is based in the hydrodynamics of turbulent 2D jets and the manner in which sediment concentration must decrease along the centerline of a plume. The only data requirement is a measurement or estimate of initial sediment concentrations by grainsize at the river mouth. The end result is a transfer function derived from the physics of plumes that allows pixels in remotely sensed images of plumes to be assigned absolute SSC values by particle size in units of kg=m. This paper therefore has the following key goals: (1) to review and extend known results for 2D turbulent jets and sediment plumes, (2) to derive bounds for how SSC must decrease along the centerline of a plume and (3) to show how these results can be used to assign SSC values in sediment plume images. Applications and efforts to validate this approach will be presented in a companion paper. r 2008 Elsevier Ltd. All rights reserved.