Monitoring and preliminary interpretation of in-river turbidity and remote sensed imagery for suspended sediment transport studies in the Humber catchment

Rivers are the main source of sediment to the marine environment in global terms. This sediment is predominantly suspended sediments. Calculation of suspended sediment flux requires the combination of suspended sediment concentration and water discharge records. A continuous record of suspended sediment concentration is derived for Land Ocean Interaction Study (LOIS) river monitoring sites using an innovative dual turbidity sensor system. Calibration of turbidity data, to provide a record of suspended sediment concentration, is achieved by comparisons with bulk water/sediment samples collected from Humber rivers, covering the full turbidity range usually encountered in British rivers. The equipment, methodologies and preliminary results are described, along with the potential errors and limitations. One of the functions of remote sensed data is to help understand the applicability of such point measurements. LOIS is using such data, acquired by imaging spectrometers mounted in an aircraft, to map the spatial distribution of suspended sediment concentration. A semi-empirical relationship has been developed between suspended sediment concentrations and the irradiance reflectance recorded in a near infra red band by the compact airborne spectral imager (CASI). The resulting data on the spatial distribution of suspended sediment concentration are illustrated by an example from the lower part of the River Ouse, Yorkshire. The next stage of the programme will integrate the field science and remote sensing studies with other LOIS rivers research on particle properties, river bank erosion and sediment source studies. (C) 1997 Elsevier Science B.V.