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Runkerry Strand, BushfootAntrim
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Summary Full report
Site Type: Coastal section
Site Status: PASSI
District: Moyle District Council
Grid Reference: C935427
Rocks
Rock Age: Quaternary (Holocene)
Interest
Other interest: No data, Beach deposit, Coastal processes, sand dune

Summary of site:

The beach at Bushfoot, Runkerry or Bushfoot Strand, absorbs more energy from ocean waves than any other in Northern Ireland. Its constantly changing morphology in response to seasonal changes in sea conditions provides a text book example of beach states.

The beach is 1.2 km long with a general north east/south west shoreline except at the north east end where it swings north to Runkerry Head. The river Bush enters the bay at the south west corner. An extensive tract of sand dunes backs the beach extending over a kilometre up the Bush valley. They appear to have developed in two phases, the older, and inland of the tramway track, thought to date to around 5 to 6,000 years ago, is characterised by a reddish colour and the younger, with paler sand, on the seaward side of the tramway, believed to date from 4,000 years ago. The dunes appear to have become inactive soon after the second phase when no new sand was added. Observed blow-outs are simply redistributing existing sand. The dunes stand on a platform of glacial deposits that protect them from modern marine erosion. This shoreline was primarily shaped by the last major glaciation (the Midlandian) as the veneer of boulder clay shows. As the ice sheets melted and unloaded the land it rose causing a fall in sea level about 12,000 years ago and then rose progressively to a maximum around 7,000 to 6,500 years ago. The dunes formed soon afterwards as wind stripped sand from the beach. The beach shows strong seasonal changes caused by destructive waves, usually at their height in winter storms and constructive waves more typical of the summer. In winter, strong winds can blow uninterrupted for over 6,000 km across the North Atlantic and this generates massive waves which comb sand from the beach and in extreme conditions can almost strip it. The sand is carried into the bay where it settles into linear mounds or bars parallel with the shore. Once establish, these bars offer a measure of protection against future storms. The large volumes of water piled against the beach escape along the troughs between the bars but the sheer volume draining seawards is such that it breaches the bars at intervals creating channels with notorious rip currents. These channels define a series of water flow cells along the shore which, in turn, determine the distribution of beach cusps (seaward pointing sand ridges on the beach) directed towards the channels. In summer wave energy is much reduced and the sand in the bars is transported shoreward onto the beach where it remains until the onset of destructive conditions with the onset of winter storms. It is believed that the rhythmic behaviour of sand reflects a fragile equilibrium readily influenced by the seasonal changes in wave energy levels. This can only be maintained while the sediment supply remains the same. At Runkerry Strand it would appear that any sediment lost from the beach to the dunes is balanced by new sediment supplied by the Bush River. This is an ideal site to study and demonstrate almost all variations in beach states and as such is worthy of designation. The greatest threats to this system are from activities that influence the sediment mass. River works affecting sediment supply and particularly the removal of sand from the beach are the most obvious and should be controlled or curtailed. Erosion of the dunes due to unconfined access is also problematic and could be limited with signposting and the development of walkways.


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