Coastal chalk cliff erosion: Experimental investigation on the role of marine factors
In this paper the marine factors of erosion contributing to the chalk cliffs located on either side of the English Channel are examined. From an analysis of the literature, the main physical phenomena determining the marine erosion of the shore platform and the foot of the cliff are considered. Field observations of the coastal chalk cliff show that the vertical erosion of the shore platform does not appear to be the main cause of cliff erosion, which is mainly governed by cliff collapse processes. To estimate the impact of waves on the base of the cliff, experiments were carried out in a wave flume. The pressure due to the waves and the dissipation of waves were measured for three simple configurations of the boundary conditions between the cliff and the sea. The pressure never exceeded the compressive strength of chalk rock. Nevertheless, pressure fluctuations due to periodic waves can induce a fatigue process within the fracture structures.
The experimental results showed that the shingle by itself has a low effect on wave energy dissipation. The main effect of shingle is to reduce the water depth at the toe of the cliff. Furthermore, it is demonstrated that a lower water depth leads to a lower impact of the waves on the cliff.
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Most of the rocky coastlines around the world are subject to active erosion processes. Because of the growing hazard to local communities from coastal cliff retreat, it is necessary to investigate where, when and how cliffs collapse. The results of these studies are vital for the planners and local authorities responsible for safety and access to cliffs and beaches. This volume focuses on the coastal chalk cliffs of the English Channel, where a multidisciplinary approach has been used to understand active coastal cliff recession.
The book is organized around three main themes: the geological factors controlling cliff instability, the marine parameters influencing coastal erosion and the use of some new tools for hazard assessments.
This volume will be of use to academics and professionals working on rocky shores, with an interest in sedimentary geology, stratigraphy, tectonics, geomorphology, engineering geology, coastal engineering and GIS.