Upon completion of the Oosterscheldekering and Oesterdam in 1986, the ebb and flow of water decreased and thus the tidal height differential was reduced from to . As a result, the shoals are no longer being naturally replenished with sand, further disrupting the ecosystem of the estuary; the shoals are used for, among other things, food for birds and resting places for seals. To help compensate for the partial loss of the tide, Rijkswaterstaat applied large amounts of sand to the Roggeplaat shoal in the northwestern part of the estuary in 2019 and 2020.
