Holocene evolution of the gravel coastline of East Sussex: discussion

In a recent issue of the Proceedings, Jennings & Smyth (1990) investigated a critical aspect of the Holocene coastal evolution of much of Britain; namely gravel (or shingle) sediment supply and beach morphodynamics through time. Their study area is the coastline of East Sussex, and it should be noted that it is only a component of the larger coastal unit (or 'master cell') between Selsey Bill and Dungeness (Fig. 1) (cf. Steers, 1964). This cell is presently characterized by a net easterly littoral drift. Chalk cliffs with associated minor headlands occur between Brighton and (the most dramatic headland) Beachy Head. While these headlands may be a barrier to littoral drift over short periods (lef years), there is no evidence for major long-term (Ur years) sediment sinks for gravel except at Dungeness, which is the largest coastal accumulation of gravel in Britain. The source of this gravel is debatable (Greensmith & Gutmanis, 1990), but it is widely considered that easterly longshore transport has made a significant contribution to the gravel volume of Dungeness during the Holocene (e.g.; Eddison, 1983). Jennings & Smyth identify several important factors in the Holocene coastal evolution of East Sussex, including the fundamental role of Pleistocene-derived gravel in the sediment budget and the much more dissected coastal form which existed earlier in the Holocene. This produced a more compartmented littoral drift system than occurs at present. They also demonstrate that the large gravel cuspate foreland called the Crumbles is a relatively ephemeral feature (see also Jennings & Smyth, 1987), a conclusion supported by earlier historic accounts (e.g.; Redman, 1852). Previous models of the coastal evolution of this area emphasized littoral drift (e.g.; Steers, 1964). Jennings & Smyth provide very different models which include a comparatively recent (800 to 300 B.P.) onshore supply of gravel at the Crumbles combined with morphodynamic changes which first favour shoreline progradation and then favour shoreline recession. These models are questionable in terms of their temporal and spatial scales and in regard to their application of morphodynamic concepts. The author would like to otIer an alternative and much simpler explanation which is consistent with