Hey Campbell. Yes, in a simplistic way, the Delfland Engine is a massive pile of sand left there to be worked by nature into reshaping the coastal environment.

The idea of using micro dredging for coastal protections along with the use renewable energy seems a very sophisticated method, one that I am not familiar with. Related projects that I am aware of are normally based on riverbanks and or curve sectors of large rivers. Mississipi river (US), and Rio Negro (Brazilian Rainforest)are two spots that such approach has worked. The use in coastal/island environments are not known by me, but with the right approach, it may be plausible.