The long-term monitoring of suspended sediment transport with side-looking Acoustic Doppler Current Profilers: a graphical user interface for echo profiles interpretation.

The idea of a long-term and reliable monitoring of suspended sediment transport (SST) is attractive for a variety of applications in fluvial hydraulics, namely in hydropower projects that need to evaluate the impact of sediment erosion and deposition in a dam reservoir. This requires measuring both flow discharge and corresponding suspended sediment concentration (SSC) to determine the SST. Many devices and techniques have been proposed about these subjects: the acoustic Doppler current profiler (ADCP) is widely applied to evaluate river discharge whereas sediment samplers are often used to sample water-sediment mixture in the river channel. However, practical limitations of the physical samplers operation (e.g. no measurements in extreme cases such as flood events) and the need to displace human and technical resources to the field reduces the available data. Consequently, engineers usually correlate SST to water level, where the latter is much easier to be continuously monitored. Unfortunately, it is not trivial to obtain correlations between SSC, flow discharge and water level due to hysteresis processes. Therefore, scientific and practical questions remain about the actual possibility of continuously measuring the SST during long periods (i.e., years). Aiming to answer these questions, this work proposes the use of a side-looking ADCP for the monitoring of flow discharge and SSC, combined with an analytical method based on the sonar equation and written as function of the attenuation-backscatter ratio. An application of this method is presented with long-time measurements made in the Devoll river, Albania. For the application of this method, a Graphical User Interface (GUI) was developed to allow non-expert users to analyze the echoes profiles from a side-looking ADCP for the assessment of the SSC.