The long-term evolution of the seaward part of mixed-energy tidal inle
t systems is analysed and modelled mathematically in terms of aggregat
ed morphological parameters. The model is an adapted version of a two-
line model, in which empirical information on the equilibrium state of
the outer delta is included. Thus detailed computations of the water
and sediment motion at the hydrodynamic time scale are avoided. The vi
ability of the concept is tested and the model is verified against dat
a from one of the inlets of the Western Wadden Sea. The results of a n
umber of practice-based applications are shown and discussed.