Velocity field in a groin field: implications for sediment and nutrients transport

Groins are devices used for riverbank protection. These macrostructures change the river flow, which impacts sediment and nutrient transport. Furthermore, in the inter-groin space, flow recirculations are observed. Aiming at characterizing the flow field in and along a groin field, a comprehensive experimental program is put forward by considering, at this stage, a river reach modeled with a fixed bed and targeting to characterize different flow parameters: mean velocity distribution, streamlines in the function of the flow rate. Using a Lagrangian technique, an analysis is carried out to determine relevant flow statistics to compute turbulent variables. Additionally, we assess the probability of particle entrapment in the inter-groin area and the distribution of residence times of particles in that area.  The scale effects and limitations of the experimental approach are presented and discussed. Future lines of work regarding the interaction between the groin field and a loose bed are discussed, improving the understanding of the transport and distribution of suspension load, contaminants, and nutrients in the river regions of groins.