The Scheldt estuary is situated in the Netherlands and Flanders/Belgium. Both countries collaborate in policy, management and research, as laid down in a treaty of 2005. Preservation of the ‘physical characteristics of the estuary’ plays an important role in formulating objectives, but it is still debated ‘what exactly should be preserved’. What exactly should be preserved’ has a diversity over the various places, as both actual values and driving forces are different along sites. A management plan in such detail is not available.

Recent research has shown which role the tidal intrusion has in these discussions. Tidal intrusion as (an indicator of the) objective for future policy (i) reflects a long term development, (ii) can be linked to changes within the estuary itself, including sediment management and (iii) can be evaluated easily, as for practically all user-functions the increase in tidal amplification is regarded as negative. As a conclusion we pose that we need to accept that from science alone we cannot expect an unambiguous answer when preservation of the ‘physical characteristics of the estuary’ is fulfilled.