CASI data utilized for mapping suspended matter concentrations in sediment plumes and verification of 2-D hydrodynamic modelling

A combined tunnel and bridge between Denmark and Sweden, The Oresund Link, is presently under construction (1995-2001). The dredging spills and environmental effects are monitored continuously. The monitoring involves the simulation of suspended matter concentrations in sediment plumes from dredging operations using 2-D hydrodynamic modelling (MIKE 21 PA/MT). A Compact Airborne Spectrographic Imager (CASI) acquisition was used to map suspended matter concentrations in a plume from 10 June 1997. Suspended matter concentrations were in the range of 1-30 mg l-1 with background concentrations around 1-3 mg l-1, while concentrations in the plume were 3-30 mg l-1. A map of suspended matter concentration was derived from an empirical algorithm between in situ irradiance reflectance at 550 nm and suspended matter concentration determined from water samples taken both inside and outside the plume. The map was used to verify the results derived by the 2-D hydrodynamic model. A comparison of the concentration variations derived using the two methods presented here shows a reasonable agreement, in spite of the fact that the remote sensing data have far more spatial details than the MIKE 21 simulation.