GlobR2C2 (Global Recession Rates of Coastal Cliffs): a global relational database to investigate coastal rocky cliff erosion rate variations

Abstract

Abstract. Rocky coast erosion (i.e., cliff retreat) is caused by a complex interaction of various forcings that can be marine, subaerial or due to rock mass properties. From Sunamura's seminal work in 1992, it is known that cliff retreat rates are highly variable over at least four orders of magnitude, from 1 to 10 mm yr−1. While numerous local studies exist and explain erosion processes at specific sites, there is a lack of knowledge at the global scale. In order to quantify and rank the various parameters influencing erosion rates, we compiled existing local studies into a global database called GlobR2C2 (which stands for Global Recession Rates of Coastal Cliffs). This database reports erosion rates from publications, cliff setting and measurement specifications; it is compiled from peer-reviewed articles and national databases. In order to be homogeneous, marine and climatic forcings were recorded from global models and reanalyses. Currently, GlobR2C2 contains 58 publications that represent 1530 studied cliffs and more than 1680 estimated erosion rate. A statistical analysis was conducted on this database to explore the links between erosion rates and forcings at a global scale. Rock resistance, inferred using the criterion of Hoek and Brown (1997), is the strongest signal explaining variation in erosion rate. Median erosion rates are 2.9 cm yr−1 for hard rocks, 10 cm yr−1 for medium rocks and 23 cm yr−1 for weak rocks. Concerning climate, only the number of frost days (number of day per year below 0 ∘C) for weak rocks shows a significant, positive, trend with erosion rate. The other climatic and marine forcings do not show any clear or significant relationship with cliff retreat rate. In this first version, GlobR2C2, with its current encompassing vision, has broad implications. Critical knowledge gaps have come to light and prompt a new coastal rocky shore research agenda. Further study of these questions is paramount if we one day hope to answer questions such as what the coastal rocky shore response to sea-level rise or increased storminess may be.

Global distribution of coastal cliffs

“…Recognized independent states without cliffs documented (to our knowledge) include: Belgium, Benin, Gabon, Guyana, Iraq, Marshall Islands, Nauru, Netherlands, Nigeria, Suriname, Togo, and Tuvalu. More recently, Prémaillon et al (2018) compiled cliff retreat rates from many regions worldwide. Sunamura (1992) compiled studies of cliff retreat located in 16 different independent states, and Moses (2013) provides a summary of additional cliff retreat rates in tropical independent states and several territories.…”

“…Sunamura (1992) compiled studies of cliff retreat located in 16 different independent states, and Moses (2013) provides a summary of additional cliff retreat rates in tropical independent states and several territories. More recently, Prémaillon et al (2018) compiled cliff retreat rates from many regions worldwide. Numerous additional cliff retreat studies have been conducted recently for individual nations, regions, or sites.…”

“…However, Luijendijk et al (2018) does not consider backshore features such as coastal cliffs, and maps beaches backed by cliffs as 'sandy shorelines'. In another recent study, Prémaillon et al (2018) used 58 publications to compile an extensive database of coastal cliff retreat rates from 16 different countries (mostly located in Europe, Oceania, and North America) totaling more than 1680 records.…”

Monitoring Cliff Erosion with LiDAR Surveys and Bayesian Network-based Data Analysis

“…Despite such difficulties, mainly connected with accessibility of high cliffs, the factors influencing cliff erosion have been investigated through quantitative numerical methods. These approaches have varied from simple correlation matrices [7] to stochastic simulations [8] and from local to continental scales [9].…”

Recent Geomorphological Evolution and 3D Numerical Modelling of Soft Clastic Rock Cliffs in the Mid-Western Adriatic Sea (Abruzzo, Italy)

“…Rock coasts on soft materials are the result of a complex combination of many endogenous and exogenous factors, such as the morphostructural and stratigraphical setting, lithology, climate, wave energy, tides, and long-term sea-level changes [1][2][3][4][5][6][7]. They are of great interest due to (1) retreat rates of 10 −2 to 10 m/yr, up to two orders of magnitude greater than hard rock cliffs [7][8][9][10][11][12][13][14][15]; (2) the localized and episodic nature of cliff recession over a short time span and almost parallel recession trend over a long time span [2,16,17]; (3) scattered and fast erosion cycles, consisting of toe erosion, cliff instability, mass movements, talus deposits, beach formation and erosion, and the resumption of toe erosion [2,7,12,17,18]. Due to the lithological variability and related strength parameters characterizing these types of cliffs, the mechanisms and processes inducing the fast retreat are largely variable and depend on several factors [2,7].…”