In the foregoing section we have focused on the dynamic equilibrium profile of the upper shoreface, temporally averaged over years and alongshore spatially averaged over about a kilometre. We philosophised that a cross-shore profile will evolve towards a (stable) equilibrium corresponding to the concurrent forcing and that disequilibrium implies that not enough time has been available to achieve equilibrium. In such an approach, the focus is on the order and regularity in the profile evolution.
On timescales shorter than a year and especially on the timescale of episodic events, we may observe highly dynamic variations of the upper shoreface profile and plan form. In this section, the emphasis is on variability and diversity instead of on order and regularity. We will first discuss the high dynamic variability of the intertidal beach and the surf zone on the timescale of events (Sect. 7.3.2). Next, we introduce the typical seasonal variations that are common on many beaches worldwide (Sect. 7.3.3). Cyclic behaviour of bars on the timescale of years is discussed in Sect. 7.3.4. Last, we focus on the impact of episodic events on a dune backed shoreface (Sect. 7.3.5). These issues are considered relevant for the safety of nearshore infrastructure and for recreational beach use.