The Mediterranean Coastal Cliff

A large portion (~40 km) of Israel’s Mediterranean coast is characterized by a steep / sub-vertical coastal cliff. The cliff comprises a sequence of late Quaternary eolianites and paleosols and reaches elevations of 50 m above sea level.  Removed by up to tens of meters from the water line, wave-scouring activity along the cliff’s base continuously de-stabilizes the cliff-face above and results in discrete and episodic cliff-collapse and retreat events. Whereas the time-averaged retreat rate of the cliff is roughly several cm/yr, localized cliff-collapse events can result in several meters of ‘instantaneous’ cliff retreat, which repeatedly impact communities and infrastructure along the coastal environment. In addition, anthropogenic coastal development can also affect the sea-cliff and potentially accelerate its erosion and retreat.
The GSI continuously monitors the natural coastal processes that affect Israel’s Mediterranean coastline, including those driving retreat of the coastal cliff and their response to natural as well as anthropogenic environmental changes. A key objective of these studies is to provide policy makers at the national and local levels with the information required for planning and mitigation purposes. The significance of achieving this objective is further highlighted by the recently approved executive decision to protect Israel’s coastal cliff from further erosion and inland retreat.

 

 


The GSI’s coastal research initiative consists of research projects focused on the shallow off-shore shelf, the shore line, the cliff, and the coastal plains above it to the east. These projects are led by a diverse team of scientists from various disciplines such as: sedimentology, paleontology, geo-engineering, pedology, geomorphology, remote sensing and geochronology.  The approaches employed include ‘classic’ methods such as field mapping, stratigraphy and core extraction, as well as newer technologies such as LiDAR (terrestrial and airborne), GPS-RTK, time-lapse photography and advanced applications of geochronology methods.
Results of these studies are significantly advancing our understanding of coastal erosion process and their rates. For example, recent results from analysis of multiple airborne LiDAR campaigns extending from 2006 until the present demonstrate that previously reported cliff-top retreat rates, which appear to suggest cliff retreat at rates of up to several m/yr since the 20th century, are artefactually increased by a sampling bias associated with observation time intervals shorter than the episodicty of retreat. Cliff retreat rates along Israel’s coast remain comparable to background retreat rates of 3-9 cm/yr. This new information has been provided to the ‘Mediterranean Coastal Cliffs Preservation Government Company’ and as the ‘scientific’ background for the planned construction of protective wave breakers. 
 


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