M.Sc.

The Morphodynamics of Bushfoot Strand

Thesis presented in part requirement for the degree of M.Sc.

School of Biological and Environmental Sciences,

The New University of Ulster

1981

Abstract Bushfoot Strand is exposed to energetic Atlantic wave and wind processes.  Cyclic transfers of sand seaward and landward occur. The sand is essentially a thin veneer resting on a coarse gravel frame and sand removal becomes apparent when the gravel is exposed.  The beach is rhythmic in nature - crescentic bars, mega-embayments, mega-cusps and beach cusps occur.  Seaward flowing rip currents are always present and are fed by converging longshore currents.  The morphological patterns are dynamic in nature and are similar to patterns in models proposed by Australian workers.  No statistically significant correlation between sub-aerial beach volume and wave power existed, but the significant correlation with mean windspeed suggests that the cycles of sediment movement are broadly seasonal in nature.  Edge waves may control the spacing of rip currents and the wavelength of crescentic bars and beach cusps, although their existence is largely inferred by the presence of these features and the existence of constraining headlands.

Rip currents at Bushfoot Strand, 1975.

D.Phil.

Holocene Coastal evolution, Co. Donegal, Ireland

Thesis submitted to the Faculty of Science, The University of Ulster,

for the degree of Doctor of Philosophy

1985

Abstract Within the context of an interdisciplinary project concerned with coastal evolution in County Donegal, Ireland, an area of little previous research, three main aspects were examined. Firstly, the nature of the intertidal peats in this area and the information they contain on relative sea-level (RSL) change. Secondly, the nature of the coastal sediment systems and thirdly, the evolution of these during the Holocene in the light of relative sea-level changes. The research showed that intertidal peat in the study area has formed under varying conditions, and in some areas, where it rests on estuarine sediments, regressive overlap is indicated. ¹⁴C dating, corroborated by by pollen analysis, was used to construct a tentative RSL framework. A mid-Holocene RSL peak in the northwest is absent in the southwest. Relative sea-level curves for the study area form a continuum which, it is suggested, is part of a larger British Isles continuum. Systems of coastal dunes, fronted by high-energy beaches, are located in compartments or at the mouths of shallow estuaries. In the latter situation, sediment, typically carbonate-rich fine sand, is circulated through a number of environments: dunes, estuaries, ebb deltas, beaches and the offshore zone. The release of sediments from dune sinks is accomplished by migrating ebb channels. Sediment is moved into new sinks, typically systems of prograded dune ridges. It is suggested that most coastal systems formed as the mid-Holocene RSL rise waned. Initial phases of gravel emplacement, sometimes drift-orientated, were succeeded by phases of dune ridge progradation and vertical growth. The second half of the Holocene, a period of relatively stable RSL, was characterised by the continued freeding ashore of sand, augmented by skeletal carbonate, into the dunes.

Air photograph of Ballyness Estuary, at the northwest tip of Donegal. The arcuate sandy beach is about 5 km long. The coastal dunes attain an elevation of 30 m (large bright area).

Comments In Donegal, the cessation of the Holocene transgression 5000 years ago meant that salt marshes could no longer grow upwards: they were transformed into freshwater bogs. Initially, glacial sediments were reworked by waves to form gravel strand plains. Later, as more and more minerogenic sediment was swept ashore, augmented by skeletal carbonate, the strand plains were buried in sand. Extensive human interference in the dune systems has formed complex systems of blowouts. Donegal contrasts with western Newfoundland. In Donegal, most of the sand in the coastal system is now in the dunes. In St. George's Bay, Newfoundland, the sand is in the adjacent barrier platform; the gravel strand plains are mostly devoid of sand. The difference is partly due to the differing sea-level histories, and partly due to the presence of deep water very close to the coast in St. George's Bay.