Morphodynamic implications for shoreline management of the western-Mediterranean sector of Egypt     

Omran E. Frihy 《Environmental Geology》2009,58(6):1177-1189

Although the western-Mediterranean coast of Egypt between Sallum and Alexandria, ~550 km long, has maintained a considerable equilibrium throughout history, developers have built traditional protective structures in an effort to form sheltered recreational beaches without taking into consideration its geomorphologic characteristics, coastal processes and their harmful impact on the coastal environment and human safety. The improper practices in this environmentally valuable region have induced us to undertake an initiative to carry out a morphodynamic analysis to provide a framework for understanding the relationship between coastal morphology and the prevailing dynamic forces. Based on the degree of natural protection or wave sheltering, the study shoreline can be categorized into four distinct morphotypical stretches: (1) high-energy wave-exposed shores and the outer margins of the rocky headlands, (2) moderate to high wave-energy beaches along semi-exposed embayments and bays mostly downdrift of the rocky headlands, (3) low-wave energy at semi-exposed headland lee-sided and pocket beaches, and (4) calm wave-sheltered enclosing water basins for safe anchorages, moorings and recreation beaches. The results deducted will have practical applications for shoreline management initiatives regarding sustained sites suitable for future beachfront development such as safe swimming conditions, sport facilities, water intakes and sheltered areas for vessels. In addition, benefits realized by the understanding of the morphodynamic processes would enhance our awareness of the significance of the role of western coast morphodynamics in supporting sustainable development via shoreline management. As far as sustainability is concerned, the selection of appropriate sites would help avoiding or minimizing the formation of the hard structures needed for creating safe recreation beaches. On a national scale, results reached could provide reliable database for information that can be used in establishing a sustainable shoreline management plan, which is, in turn, an essential part when implementing an Integrated Coastal Zone Management Plan for this region of attraction.  相似文献   

A new hazard zonation methodology applied to residentially developed sea-cliffs with very low erosion rates,East Coast Bays,Auckland, New Zealand     

R. Jongens  J. Gibb  B. V. Alloway 《Natural Hazards》2007,40(1):223-244

A new hazard zonation methodology is applied to the East Coast Bays area of North Shore City, one of the most residentially developed cliffed shorelines in New Zealand. It is based on a series of geotechnical cliff profiles from three pilot study areas (George Gair Lookout, Rahopara Reserve–Kennedy Memorial Park, and Mairangi Bay–Rothesay Bay) which detail many of the variables that influence overall cliff stability. The methodology requires calculation of a Coastal Landslide Hazard Zone (CLHZ) width for each geotechnical profile and is derived by quantifying three factors: the rate of long-term sea-cliff retreat; the amount of horizontal retreat expected from either joint block fall, fault plane failure, or bedding plane failure, coupled with the amount of horizontal retreat resulting from slumping of the top weathered layer; and a safety factor. The rate of long-term sea-cliff retreat is multiplied by a hazard assessment period of 100 years, which is then added with the two other factors to derive a CLHZ width. Finally, the widths are entered into a Geographic Information System (GIS) to delineate a hazard zone. Owing to the very low rates (< 0.1 m a⁻¹) of sea-cliff retreat in the East Coast Bays area, the long-term rate of sea-cliff retreat at each profile location could not be quantified by conventional survey techniques. Instead, a Sea-cliff Vulnerability Index (SVI) was employed to quantify the long-term rate. Weighted variables considered in the SVI include the bedding dip direction, the occurrence of faults and their orientation, sea-cliff aspect, cliff-toe and cliff-face lithology, cliff-top height, and the presence of groundwater seepage. Calculated CLHZ widths along East Coast Bays range between 13 m and 34 m inland of a reference cliff-line in response to spatial variations of the sea-cliff geology and morphology. The widths reflect the estimated degree of risk over the next 100 years from coastal erosion and landslips.  相似文献