The sand bar eroded as planned, but the direction of transport was different than initially predicted. This example shows that steering of wave- and current-induced sand transport is not easy and that specific knowledge is needed to predict it.
Wether the level of this knowledge was sufficient at the time of the Workumerbuitenwaard nourishment is doubtful. In the meantime, science has advanced and a more recent nourishment at virtually the same location seems to behave more or less in line with the predictions. The area where most of the sand was deposited, west of the original bar, became more suitable for water plants.
The local processes taken into account in the prediction seem to be subordinate to regional processes such as larger-scale currents and water level gradients which play a role in the sand transport near the Workumerbuitenwaard. These lessons have been taken into account in the design for the Sand Engine IJsselmeer coast.