Hard-Rock Coastal Modelling: Past Practice and Future Prospects in a Changing World

Alan S Trenhaile

doi:10.3390/jmse7020034

Abstract

This paper reviews the history of conceptual and numerical modelling of hard rock coasts (mean annual cliff erosion typically < 1 mm up to 1 cm) and its use in studying coastal evolution in the past and predicting the impact of the changing climate, and especially rising sea level, in the future. Most of the models developed during the last century were concerned with the development and morphology of shore-normal coastal profiles, lacking any sediment cover, in non-tidal environments. Some newer models now consider the plan shape of rock coasts, and models often incorporate elements, such as the tidally controlled expenditure of wave energy within the intertidal zone, beach morphodynamics, weathering, changes in relative sea level, and the role of wave refraction and sediment accumulation. Despite these advances, the lack of field data, combined with the inherent complexity of rock coasts and uncertainty over their age, continue to inhibit attempts to develop more reliable models and to verify their results.

Highlights

Rock coasts serve as: depositories for paleo-environmental evidence; sediment sources for commercially valuable and environmentally sensitive estuaries, marshes, and beaches; tourist destinations, when rocky foreshores are covered by beach sands; and bulwarks that protect increasingly densely populated coastal hinterlands from erosion and flooding [1,2,3]
Researchers need to acquire a better understanding of rock coast dynamics and evolution, in part to predict and mitigate the effects of rising sea level and possibly greater storminess during this century
The results suggested that the fall in sea level from its mid-Holocene maximum, 1 to 2 m above its present level, promoted the formation of subhorizontal platforms in Australasia and over much of the Southern Hemisphere, whereas an asymptotic rise in sea level over much of the Northern Hemisphere was more conducive to the development of sloping platforms [35]

Summary

Introduction

Rock coasts serve as: depositories for paleo-environmental evidence; sediment sources for commercially valuable and environmentally sensitive estuaries, marshes, and beaches; tourist destinations, when rocky foreshores are covered by beach sands; and bulwarks that protect increasingly densely populated coastal hinterlands from erosion and flooding [1,2,3]. Researchers need to acquire a better understanding of rock coast dynamics and evolution, in part to predict and mitigate the effects of rising sea level and possibly greater storminess during this century. Modelling is a ffuundamental and appropprriiaattee ttoooll to study changes in rock coasts in the past and to predict likely changes in the future [4,5]. WWhheerreeaass tthhee sseeccttiioonnaall sshhaappee iiss ggeenneerraallllyy aassssuummeedd ttoo bbee ccoonnttrroolllleedd bbyy tthhee rreellaattiioonnsshhiipp bbeettwweeeenn rraatteess ooff wwaavvee aatttteennuuaattiioonn aanndd tthhee gradient of the bottom, the plan shape is thought to reflect the effect of headland-bay morphology on wave refraction and the protection afforded by accumulating beach material in the bays. Eng. 2019, 7, 34 gradient of the bottom, the plan shape is thought to reflect the effect of headland-bay morphology on wave refraction and the protection afforded by accumulating beach material in the bays

Coastal Profiles

Coastal Plan-Shape

Changes in Relative Sea Level

Equilibrium

Modelling Constraints and Limitations

Conclusions