Hydro-ecological relations in the Delta Waters

Erosion by waves of sandy shoals (conform Section 3.2) was very oomon
from 1971 onwards; shore faces retreated at a rate of maximum
10 mlyear. After most of the shores successively have been protected
against sroeion, Che total loss of shoals and &fiats in L988 has been
calculated as 54 ha or 6 percent of
(Leeuwestein and Schoot. 1988; Fortuin. 1989).
the original total area
Although the fomer tidal channels tend to silt up, hardly any
sedimentation is observable since the only soure of sediWut,
represeated by the ssudy shoals and mudflats, laqely hae been
protected against erosion. Comeqnently future changes of the basin's
tidal landscape vul be very limited.
The sbift in driving force on GrsYelingen'~ ebb tide1 delta since 1971
largely is comparable to that previously described at the Hatingvliet
(see Section 3.2). As to be espected a similar motphoLogica1
development initiated by similar mechanisms has been pbserved. Erosion
of the deltafront related ts an expansion ~f sandy shoals and silting
n~ Q£ foruer tidal channel ever the last 20 years clearly is
fllustrated by Fiwes 8 and 9.
The tendencies ~f future changes of the ebb eidal delta are comparable
to the Barievliet case.
Figure 8 Cross sections of the deltafront on the Grevelingen ebb tidal
delta (1960-1980), Uwstrating the impact of closing the
estuary in 197 1 (mhsiek and Mulder, 1989)