Coastal cliff retreat rates at Beit-Yannay, Israel, in the 20th century

摘要

Research indicates that the aeolianite (Kurkar) cliffs along the Israeli Mediterranean coastline have continuously retreated eastward during the last few decades. There seems to be no dispute among Earth scientists regarding the general trend of cliff retreat. However the majority of papers displaying cliff retreat rates are based upon comparison of aerial photographs. Their lack of advanced geometric measurement methods causes a high margin of error. Public attention is focused upon the Beit-Yannay coastal cliff since private homes are located along the southern section of the cliff crest. The current research compares the historic location of the cliff crest edge at Beit-Yannay as observed in a series of aerial photographs taken during the period 1918-2000. Quantitative measurement methods included applications of satellite geodesy and digital photogrammetry and mapping. Research results offer quantitative, consecutive and highly accurate data regarding retreat rates over a relatively long period of 82 years. It is concluded that: 1. Annual average cliff retreat rates of the cliff crest is 20 cm/year. 2. Categorization of the study time span reveals periods displaying varying retreat rates such as 27 cm/year during 1918-1946, 21 cm/year during 1946-1973 and 10 cm/year during 1973-2000. 3. Maximum retreat distances of the cliff crest, over the study period were found to be approximately 25 m along the northern, lowest section of the cliff. Minimum distances of 11 m were identified at the highest, southern section of the cliff. 4. The eolianite (Kurkar) cliffs along the Israeli Mediterranean coast throughout the 20th century have been an important source of sediment, contributing approximately 24 * 106 m3 of sediments to the sediment balance of Israeli beaches.