Mechanisms associated with the erosion of sand dune cliffs, Magilligan, Northern Ireland

Abstract

A fifteen year history of coastal dune recession at Magilligan, Northern Ireland has revealed both time and space contrasts in processes and morphology. Since 1968 'storm' frequency has increased, while dune retreat reached a peak (5.4 m) in [1978][1979]. Three types of dune eroding events are noted, resulting from particular wave/wind/tide combinations. The spatial variability in dune scarping is associated with vegetation and soil development, and slope failures range from granular avalanches to retrogressive rotational slumps.

Laboratory investigation of beach scarp and dune recession due to notching and subsequent failure

“…The undercutting leads to a state of tension in the upper part with visible tension cracks parallel to the face. This can readily be observed in beach scarps undergoing attack by swash waves, but is also a common mechanism of dune recession as pointed out by Carter and Stone (1989). The resulting overhang generated by the tensile crack alters the balance of forces and eventually succumbs to a mass failure whereby a slab of sand slides downward or topples over leaving a vertical face.…”

Foredune accretion under offshore winds

“…The beach has experienced alternating periods of accretion and erosion over the last decades. The tallest seaward dune crest, running nearly the entire length of the beach, appears to be an old erosional escarpment formed during a 1980 storm (Carter and Stone, 1989). (Figure 1) …”

Sensitivity analysis of climate change impacts on dune erosion: case study for the Dutch Holland coast

“…SLR may impact the hydrology in the dunes and, together with changes in temperature and rainfall, alter vegetation patterns. Vegetation patterns influence the size of the avalanches during erosion events (Carter and Stone 1989). Future work should therefore also focus on climate change effects on coastal recovery and eco-physical feedback.…”

“…Other hydrodynamical variables (H ss , H inf , z s , and the cross-shore velocity u) are approximately the same for different θ . The large v-velocities enhance sand stirring (e.g., Thornton et al 1996) (Carter and Stone 1989) show that dune erosion is a non-continuous process and accidental large parts of sand are eroded from the dunes. The eroded sand had to be removed from the dune foot, in order to make the dune front unstable again and to facilitate the next mass movement.…”