To evaluate the success of this new disposal strategy an extensive monitoring programme was set up . Frequent (2-weekly up to two-monthly) topo-bathymetric surveys using multibeam echo sounding are performed in combination with seasonal sedimentation-erosion measurements using both RTK (intertidal) and singlebeam (subtidal). Also flow velocities on 10 transects, each consisting of 4 measurements points, in the shallow subtidal and the intertidal zone near the disposal locations are monitored using ADCP’s (Nortek – AquaDopp). The ADCP devices on the intertidal zone are dug in the sandbar and look upward, allowing maximal vertical resolution when flooded during the tidal cycle.
Parallel with the monitoring, a validated 2D-numerical hydrodynamic model is used to evaluate the effects of the disposal of sediments. Every three months, a simulation is performed using the most recent topo-bathymetry. This allows an evaluation of the changes in flow velocities and flow patterns near the disposal areas.
A special “protocol” (see Depreiter et al., 2012) with several criteria was developed to evaluate the monitoring results and the success of the new disposal strategy.