An integrated suspended sediment transport monitoring and analysis concept

A new integrated suspended sediment monitoring strategy applying direct and indirect technologies is presented. Optical sensors continuously record the turbidity at one point in the channel cross section close to the river bank and are calibrated by water samples taken close to the sensor. Additionally measurements are performed to establish the distribution of suspended sediment in a cross section (bottle samples combined with acoustic devices). Using correction factors (probe and cross-sectional factor) these monitoring methods are combined and it is, thus, possible to fully document the temporal and spatial variability of the suspended sediment transport and to estimate the suspended sediment load for certain time periods. This monitoring strategy was implemented at various measurement sites in Austria as well as at the Hainburg Road Bridge site on the Danube River. It has already been successfully applied for three years at this measurement site and suspended sediment loads during high discharges up to a 15 year flood event have been monitored. To evaluate the new monitoring methods the results were compared with load estimation methods found in the literature including averaging and ratio estimators as well as rating curves. The results prove that with the new methodology, the temporal variability of the suspended sediment transport can be detected more accurately compared with the other methods. They also demonstrate that the additional consideration of the spatial distribution of the suspended sediment concentration in the cross section is crucial as the mean concentration in the cross section can significantly exceed the concentration near the banks, especially at large rivers like the Danube River.