Pre- and post-beach response to engineering hard structures using Landsat time-series at the northwestern part of the Nile delta,Egypt |
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Authors: | Kh Dewidar O Frihy |
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Institution: | (1) Faculty of Science, Department of Environmental Science, Mansoura University, Box 34517, New Damietta City, Egypt;(2) Coastal Research Institute, 15 El Pharaana Street, 21514 Alexandria, Egypt |
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Abstract: | Analyses have been undertaken to examine shoreline positions established from remote sensing data along the northwestern part
of the Nile delta from the Abu Qir Bay to Gamasa embayment (∼143 km length). The image data used (MSS, TM and ETM+ sensors)
are acquired at unequal intervals between 1972 and 2006, i.e., covering a time span of 34 years. Automated waterline positions
extracted from Landsat satellite images during this period of time were computer generated. A digital shoreline analysis software
was used to calculate the annual rate of beach changes at 1,432 cross-shore transects prior to (1972–1990) and after protection
(1993–2006). On comparison, rates estimated from three statistical approaches (the end point rate, the Jackknife and a weighted
linear regression) at corresponding positions are successfully validated with those measured from ground survey. Before protection,
results reveal longshore patterns wherein erosion along a coastal stretch gives way to accretion in an adjacent stretch, refining
the sub-cells previously identified within the littoral system of the delta. Maximum shoreline retreat occurs along the Rosetta
promontory (−138.52 m/year) and along the central bulge of the delta at Burullus headland (−6.07 m/year). In contrast areas
of shoreline accretion exist within saddles or embayments between the promontories at west Abu Qir Bay (20.04 m/year), Abu
Khashaba saddle (16.17 m/year) and Gamasa embayment (20.68 m/year). These rates of changes have been significantly altered
by the construction of intensive shoreline protective structures built from 1990 to combat areas of rapid erosion at both
the Rosetta promontory and Burullus–Baltim headland, ∼15-km length in total. |
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Keywords: | Hard structures Shoreline retreat Coastal processes Shoreline mapping |
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