Fig. 8b shows the associated non-dimensional cliff toe retreat rates.
With no sea-level rise the resistant layer remains positioned about
MSL and the retreat rate stabilises over time. An increase in the rate of
sea-level rise increases recession rates as the greater water depths enable
larger waves to attack the cliff toe. Furthermore, the resistant
layer becomes submerged below low tide (for example after approximately
1000 yrs with a 1 mm/yr sea-level rise). Consequently, retreat
rates for sea-level rise scenarios take longer to reach dynamic equilibrium
owing to the overlying weaker material becoming involved in the
erosion process. In a contrasting scenario not reported here, it was
shown that a more resistant layer situated further up the cliff profile would result in a decline in rates of retreat when the rising sea reached
that level.