The Estimation of Suspended Solids Concentration from an Acoustic Doppler Current Profiler in a Tidally Dominated Continental Shelf Sea Setting and Its Use as a Numerical Modelling Validation Technique

Reliable coastal and offshore sediment transport data is a requirement for many engineering and environmental projects including port and harbour design, dredging and beach nourishment, sea shoreline protection, inland navigation, marine pollution monitoring, benthic habitat mapping, and offshore renewable energy (ORE). Novel sediment transport numerical modelling approaches allow engineers and scientists to investigate the physical interactions involved in these projects both in the near and far field. However, a lack of confidence in simulated sediment transport results is evident in many coastal and offshore studies, mainly due to limited access to validation datasets. This study addresses the need for cost-effective sediment validation datasets by investigating the applicability of four new suspended load validation techniques to a 2D model of the south-western Irish Sea. This involves integrating an estimated spatial time series of suspended solids concentration (SSCsolids) derived from acoustic Doppler current profiler (ADCP) acoustic backscatter with several in situ water sample-based SSCsolids datasets. Ultimately, a robust spatial time series of ADCP-based SSCsolids was successfully calculated in this offshore, tidally dominated setting, where the correlation coefficient between estimated SSCsolids and directly measured SSCsolids is 0.87. Three out of the four assessed validation techniques are deemed advantageous in developing an accurate 2D suspended sediment transport model given the assumptions of the depth-integrated approach. These recommended techniques include (i) the validation of 2D modelled suspended sediment concentration (SSCsediment) using water sample-based SSCsolids, (ii) the validation of the flood–ebb characteristics of 2D modelled suspended load transport and SSCsediment using ADCP-based datasets, and (iii) the validation of the 2D modelled peak SSCsediment over a spring–neap cycle using the ADCP-based SSCsolids. Overall, the multi-disciplinary method of collecting in situ metocean and sediment dynamic data via acoustic instruments (ADCPs) is a cost-effective in situ data collection method for future ORE developments and other engineering and scientific projects.