Only time can 'create' saltmarshes. I suspect that once they have been destroyed - oh, sorry -'reclaimed' - they will take many centuries to regenerate.

Although this project is better than what went before (or possibly it's purely pragmatic as some bunch of politicians/ bureaucrats, somewhere, have finally grasped what will really happen when sea levels start to rise) it still smacks of arrogance - "we know what's best for nature and we can engineer whatever habitsts we like just where we want them". This attitude was always bollocks and it's bollocks now!