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1.
The coastal zone of the Nile Delta is a promising area for energy resources and industrial activities. It also contains important
wetland ecosystems. This coastal area witnessed several changes during the last century. A set of four satellite images from
the multi-spectral scanner (MSS), thematic mapper (TM) and Systeme Pour l’Observation de la Terre (SPOT) sensors were utilized
in order to estimate the spatio-temporal changes that occurred in the coastal zone between Damietta Nile branch and Port-Said
between 1973 and 2007. Image processing applied in this study included geometric rectification; atmospheric correction; on-screen
shoreline digitizing of the 1973 (MSS) and 2007 (SPOT) images for tracking the shoreline position between Damietta promontory
and Port-Said; and water index approach for quantifying Manzala lagoon surface area change using 1973 (MSS), 1984 (TM) and
2003 (TM) images. Results showed that coastal erosion was severe near Damietta promontory and decreased eastward, however,
accretion was observed near Port-Said. About 50% of the coastal strip was under erosion and 13% was under accretion. In addition,
a remarkable decline (34.5%) of the Manzala lagoon surface area was estimated. These changes were attributed mainly to the
control of the River Nile flooding and the land use change by anthropogenic activities. 相似文献
2.
《China Geology》2018,1(4):512-521
Shandong has more than 70% of natural coasts are under erosion. Coastal erosion started from the 1970’s and became a very serious problem at 1990’s. The dramatic decrease of sediment supplies from rivers caused rapid erosion at the delta and estuary areas, especially in the abandoned Yellow River Delta. Most sandy coasts along the Peninsula were eroded due to lack of sand supply and interruption of alongshore sediment drift, sand dredging from the beach or the offshore area caused serious erosion during short time. Sea-level rise causes slow but constant shoreline retreats and became a more serious threat. Different types of hard solutions for coastal protection against erosion were used in Shandong. Seawalls are most widely used, especially at the Yellow River Delta and city center waterfront. Groynes, jetties and breakwater are used on the north and east sandy coast of the Peninsula. Hard approaches are effective to protect the coast erosion but not change the erosion causes and led secondary impact on the coast. Soft engineering solution or the combined solutions are taken into acts. Beach nourishment is mostly considered as the better soft solution, especially to those tourists attracting sandy beaches along the Shandong coast. Long term monitoring and continuous lessons learning from the coastal erosion management will be adaptive for better coast solution in the future. 相似文献
3.
Omran E. Frihy 《Natural Hazards》1984,5(1):65-81
Studies of the Nile Delta coast have indicated wide values of local subsidence, ranging from 0.4 to 5 mm/yr. Trend analysis of sea-level rise and shoreline retreat at two Nile Delta promontories have been studied. Records from tide gauges at Alexandria (1944–1989) and Port Said (1926–1987), north of the Nile delta coast, indicate a submergence of the land and/or a rise of the sea-level of 2 and 2.4 mm/yr, respectively.Dramatic erosion has occurred on some beaches of the Nile Delta. This is greatest at the tips of the Rosetta and Damietta promontories, with shoreline retreat up to 58 m/yr. Relationship between the shoreline retreat and sea level trends in terms of correlation analysis and application of the Bruun Rule indicates that the sea level rise has, by itself, a relatively minor effect on coastal erosion. The sea-level trend at the Nile delta coast is found to be only one of several effects on shoreline retreat. Major recent effects include a combination of cut-off of sediment supply to the coast by damming the River Nile and local hydrodynamic forces of waves and currents. Estimates of local future sea-level rise by the year 2100 at Alexandria and Port Said, respectively, is expected to be 37.9 and 44.2 cm. These expectations, combined with other factors, could accelerate coastal erosion, inundate wetlands and lowlands, and increase the salinity of lakes and aquifers. 相似文献
4.
Omran E. Frihy 《Natural Hazards》1992,5(1):65-81
Studies of the Nile Delta coast have indicated wide values of local subsidence, ranging from 0.4 to 5 mm/yr. Trend analysis of sea-level rise and shoreline retreat at two Nile Delta promontories have been studied. Records from tide gauges at Alexandria (1944–1989) and Port Said (1926–1987), north of the Nile delta coast, indicate a submergence of the land and/or a rise of the sea-level of 2 and 2.4 mm/yr, respectively. Dramatic erosion has occurred on some beaches of the Nile Delta. This is greatest at the tips of the Rosetta and Damietta promontories, with shoreline retreat up to 58 m/yr. Relationship between the shoreline retreat and sea level trends in terms of correlation analysis and application of the Bruun Rule indicates that the sea level rise has, by itself, a relatively minor effect on coastal erosion. The sea-level trend at the Nile delta coast is found to be only one of several effects on shoreline retreat. Major recent effects include a combination of cut-off of sediment supply to the coast by damming the River Nile and local hydrodynamic forces of waves and currents. Estimates of local future sea-level rise by the year 2100 at Alexandria and Port Said, respectively, is expected to be 37.9 and 44.2 cm. These expectations, combined with other factors, could accelerate coastal erosion, inundate wetlands and lowlands, and increase the salinity of lakes and aquifers. 相似文献
5.
Mahmoud M. El Banna 《Environmental Geology》2008,54(6):1291-1299
Types, distribution, and origin of recent sand dunes between Rosetta and Idku, in the western sector of the Nile Delta, Egypt
were investigated. Sand samples from the dunes, beach, and seafloor were studied for grain size distribution and mineralogical
composition. It has been found that most of the dunes in the study area have been subjected to deterioration and removal due
to the construction of buildings and the International Coastal Highway. The remnant constitutes a damaged belt of foredunes
that extends from El Bouseily village to the west of Idku town. The dune’s origin is interpreted to be the result of coastal
drifting and the subsequent transport of sediments of the former Canopic Nile branch eastward by the predominant longshore
current and by aeolian processes. The blown sand grains accumulated to form a belt of coastal sand dunes of original longitudinal
and crescentic forms. Urbanization of the coast has severely altered the landscape. The study area is considered vulnerable
to the impacts of climate change and the expected rise in sea level. The outcome of potential sea level rise is serious; erosion
problems are expected to be exacerbated and vast areas from land and property would be lost. Thus, protection and preservation
the remaining dunes in the study area are vital requirements for shore protection. 相似文献
6.
Natural and anthropogenic influences in the northeastern coast of the Nile delta,Egypt 总被引：4，自引：0，他引：4
Landsat enhanced thematic mapper imagery (ETM) of 2002 and aerial photography of 1955, combined with published charts and
field observations were used to interpret coastal changes in the zone between Kitchener drain and Damietta spit in the northeastern
Nile delta, previously recognized as a vulnerable zone to the effects of any sea level rise resulting from global warming.
The interpretation resulted in recognition of several changes in nine identified geomorphological land types: beach and coastal
flat, coastal dunes, agricultural deltaic land, sabkhas, fish farms, Manzala lagoon, saltpans, marshes and urban centers.
Reclamation of vast areas of the coastal dunes and of Manzala lagoon added about 420 km2 to the agricultural deltaic land.
About 48 km2 of backshore flats, marshes, salt pans and Manzala lagoon have been converted to productive fish farms. The main
urban centers have expanded; nearly 12.1 km2 have been added to their areas, and new urban centers (Damietta harbor and the New Damietta city) with total area reach of
~35.3 km2 have been constructed at the expense of vast areas of Manzala lagoon, coastal dunes, and backshore flats. As a consequence
of human activities, the size of Manzala lagoon has been reduced to more than 65%. Shoreline changes have been determined
from beach profile survey (1990–2000), and comparison of 1955 aerial photographs and ETM satellite image of 2002 reveal alongshore
patterns of erosion versus accretion. The short-term rate of shoreline retreat (1990–2000) has increased in the downdrift
side of Damietta harbor (≃14 m/year), whereas areas of accretion exist within the embayment of Gamasa and in the shadow of
Ras El Bar detached breakwaters system, with a maximum shoreline advance of ~15 m/year. A sandy spit, 12 km long, has developed
southeast of Damietta promontory. These erosion/accretion patterns denote the natural processes of wave-induced longshore
currents and sediment transport, in addition, the impact of man-made coastal protection structures. 相似文献
7.
In recent years, a new model for deposition of sand bodies in a shelf environment has appeared. This model, known as the shelf sand-plume model, is hypothesized to result from storm-driven currents that are deflected around a deltaic headland, stripping sand from the headland and redepositing it in a downcurrent ‘plume’ on the inner shelf. The modern analogue for this model is considered to be an arcuate shelf sand body located off the Damietta branch of the Nile Delta. However, the distribution of older deltaic and shoreline sands probably controls the arcuate outline of the sand body. The present current system has certainly reworked these sands into ridges and large-scale bedforms but is not responsible for the overall outline of the sand body. Grain-size range and distribution of sand on the shelf demonstrate that the source of sand in the Nile shelf sand body is not the modern Damietta headland as postulated by the shelf sandplume model. In our view, the shelf sand-plume model is presently unsubstantiated and has orginated as a misapplication of the original Nile example. As a geological model, the shelf sand-plume model lacks a set of observable, consistently applicable criteria. The only common denominator to the model is the ‘plume’ geometry of a sand body located off a deltaic promontory. However, workers postulating the existence of shelf sand-plumes have neither clearly established a ‘plume’ geometry nor shown the juxtaposition of these bodies with respect to coeval deltaic headlands in their outcrop or subsurface examples. The model does not provide criteria to distinguish a ‘shelf sand-plume’ from other classes of shelf sand bodies, notably sand ridges and storm-generated sheet-like sands. Its application to the rock record should be re-evaluated. 相似文献
8.
Alexandria-Nile Delta coast,Egypt: update and future projection of relative sea-level rise 总被引：1，自引：1，他引：0
Omran El Sayed Frihy Essam A. Deabes Samy M. Shereet Farid A. Abdalla 《Environmental Earth Sciences》2010,61(2):253-273
Previous studies have indicated that the Nile River deltaic plain is vulnerable to a number of aspects, including beach erosion,
inundation, and relatively high rates of land subsidence. This issue motivates an update and analysis of new tide-gauge records,
from which relative sea-level changes can be obtained. Estimated rates from five tide gauges are variable in terms of magnitude
and temporal trend of rising sea level. Analysis of historical records obtained from tide gauges at Alexandria, Rosetta, Burullus,
Damietta, and Port Said show a continuous rise in mean sea level fluctuating between 1.8 and 4.9 mm/year; the smaller rate
occurs at the Alexandria harbor, while the higher one at the Rosetta promontory. These uneven spatial and temporal trends
of the estimated relative sea-level rise (RSLR) are interpreted with reference to local geological factors. In particular,
Holocene sediment thickness, subsidence rate and tectonism are correlated with the estimated rates of relative sea-level change.
From the relatively weak correlation between them, we presume that tectonic setting and earthquakes, both recent and historical
ones, contribute more to accelerated RSLR than that of dewatering and compression/dewatering of Holocene mud underlying the
Nile Delta plain. As a result, large areas of the coastal plain have been subsided, but some sectors have been uplifted in
response to tectonic activities of thick underlying older strata. Projection of averaged sea-level rise trend reveals that
not all the coastal plain of the Nile Delta and Alexandria is vulnerable to accelerated sea-level rise at the same level due
to wide variability of the land topography, that includes low-lying areas, high-elevated coastal ridges and sand dunes, accretionary
beaches, and artificially protective structures. Interaction of all aspects (tectonic regime, topography, geomorphology, erosion
rate, and RSLR rate) permitted to define risk areas much vulnerable to impacts of sea incursion due to accelerated sea-level
rise. 相似文献
9.
William M. Marsh 《Environmental Geology》1990,16(2):155-164
Although limited in coverage, perched sand dunes situated on high coastal bluffs are considered the most prized of Great Lakes dunes. Grand Sable Dunes on Lake Superior and Sleeping Bear Dunes on Lake Michigan are featured attractions of national lakeshores under National Park Service management. The source of sand for perched dunes is the high bluff along their lakeward edge. As onshore wind crosses the bluff, flow is accelerated upslope, resulting in greatly elevated levels of wind stress over the slope brow. On barren, sandy bluffs, wind erosion is concentrated in the brow zone, and for the Grand Sable Bluff, it averaged 1 m3/yr per linear meter along the highest sections for the period 1973–1983. This mechanism accounts for about 6,500 m3 of sand nourishment to the dunefield annually and clearly has been the predominant mechanism for the long-term development of the dunefield. However, wind erosion and dune nourishment are possible only where the bluff is denuded of plant cover by mass movements and related processes induced by wave erosion. In the Great Lakes, wave erosion and bluff retreat vary with lake levels; the nourishment of perched dunes is favored by high levels. Lake levels have been relatively high for the past 50 years, and shore erosion has become a major environmental issue leading property owners and politicians to support lake-level regulation. Trimming high water levels could reduce geomorphic activity on high bluffs and affect dune nourishment rates. Locally, nourishment also may be influenced by sediment accumulation associated with harbor protection facilities and by planting programs aimed at stabilizing dunes. 相似文献
10.
Evolution of the modern Nile delta promontories: development of accretional features during shoreline retreat 总被引：1，自引：0，他引：1
The active accretional features that have developed along the modern Nile Delta promontories during shoreline retreat are analysed using topographic maps, remote imagery, ground and hydrographic surveys, together providing 15 time-slice maps (1922–2000) at Rosetta and 14 time-slice maps (1909–2000) at Damietta. Small double sandy spits developed and persisted at Rosetta between 1986 and 1991. At Damietta, a much larger single spit, 9 km long, formed approximately east of the mouth of the Damietta Nile branch between 1955 and 1972, although its source has now been depleted. Both the Rosetta and Damietta inlets are associated with submerged mouth bars that accumulated prior to the damming of the Nile, but that continue to contribute to local sedimentation problems, particularly at Rosetta. The development of the active accretional features along the Nile promontories reflects a combination of factors including sediment availability, transport pathways from source areas, a decrease in the magnitude of Nile flood discharges, as well as the impact of protective structures at the river mouths. 相似文献
11.
The Port of New York/New Jersey is naturally shallow, and therefore dredging is required to maintain depths necessary for navigation. About six million cubic yards of material must be dredged annually to maintain navigation channels and berthing areas. Opportunities for disposal of dredged materials in the metropolitan region are limited. The existing ocean disposal site that has, until recently, received the majority of dredged materials is nearing capacity. Under the new, more stringent, guidance for ocean disposal, a large percentage of the dredged material is not considered acceptable for ocean disposal because of contamination. This paper explores nondredging alternatives to reduce the volume of materials to be dredged, thus reducing the disposal volume. These alternatives include short-term options (e.g., reprofiling operations, in which sediments from high spots in berths are dragged to depressions in lower spots) and long-term sedimentation minimization options (e.g., subsurface berms or air bubblers deployed around berths and interpier areas). These methods require an understanding of sedimentation/circulation patterns of the harbor as a whole and the local area in which the specific methodology may be employed. 相似文献
12.
John F. Tavolaro 《Environmental Geology》1984,6(3):133-140
The purpose of this study was to quantify the dry mass of dredged material involved in each stage of typical clamshell dredging
and ocean disposal activities in order to identify and quantify “losses” of dredged material Turbidity plumes generated at
dredging sites were also observed Approximately 2% of the dredged material was lost at the dredging site Of this quantity
61% was due to the dredging itself and 38% was due to intentional barge overflow Approximately 3 7% of the dredged material
was lost at the Mud Dump Site during disposal Total loss of dredged material during these clamshell dredging and ocean disposal
operations was calculated to be 5 6% Observations revealed that turbidity plumes were local features which traveled along
the bottom for several hundred feet These plumes only persisted while dredging was occuring, and ambient conditions were established
within a relatively short time after dredging ceased 相似文献
13.
This paper deals with the types, distribution and origin, of recent sand dunes in the coastal sector extending between El Burullus Lake and the Damietta Nile River branch, Egypt. Sand samples were studied for grain size distribution and mineralogical composition. It has been found that most of the dunes in the study area have been subjected to deterioration and removal due to the construction of summer resort buildings and making the international coastal highway. The remnant constitutes a belt of foredunes on the shore of Baltium extending westward to Burg El Burullus village.The dunes origin is interpreted as the result of coastal drifting and the subsequent transport of the former Sebennitic Nile branch sediments eastward by the predominant longshore current and by Aeolian processes. The blown sand grains accumulated to form a belt of coastal sand dunes with longitudinal and crescentic forms. Urbanization of the coast has severely altered the landscape. Gaps and damaged dunes are included within the dune belt. The dunes natural cycle of advance and retreat is upset and attains its destruction phase. The consequences of its destruction are numerous and lead to hazardous impacts on the shoreline, coastal building and the nearby international highway. 相似文献
14.
Mahmoud M. El Banna 《Environmental Geology》2007,52(1):41-49
Beach profile data, covering the coast of Ras El Bar, northeast Nile Delta, collected during the years from 1990 to 2002 combined
with landsat images for the area and sedimentological investigation have been used to identify beach and nearshore seafloor
sediment changes. Along the coast of Ras El Bar, two accretion sectors and one of erosion have been recognized. The first
accretion sector is located west of Damietta harbour, where the harbour jetties have halted the littoral transport, while
the second one is behind a system of detached breakwaters protecting Ras El Bar resort. Both the two sectors are characterized
by growing shoreline with maximum rates ∼15 and 10 m/year, respectively. Also, they have maximum nearshore seafloor accretion
rates of ∼18 and 22 cm/year, respectively. The erosion sector is located east of Damietta port and has a maximum rate of shoreline
retreat ∼−10 m/year. Erosion of its nearshore seafloor is indicated recording a maximum rate of ∼−20 cm/year. The rate of
net sediment volume change in the area indicates shifting of the accretion sector (II) westward, responding to installation
of the new breakwaters unit. The two accretion sectors are characterized by dominance of moderately sorted fine sands in their
shore area which change seaward into less sorting very fine sands. Beach sands of the eroded sector are poorly sorted medium
grain size. The dominant constituents of heavy mineral species in beach and sea-bottom sands are the characteristic assemblages
of the Nile deposits. The sands of the eroded zone are relatively enriched in monazite, zircon, tourmaline, garnet, and rutile. 相似文献
15.
Nalin Prasanna Ratnayake Amila Sandaruwan Ratnayake P. V. Keegle M. A. K. M. Mallawa Arachchi H. M. R. Premasiri 《Environmental Earth Sciences》2018,77(1):24
Man-made coastal structures directly affect sediment balance and sediment dynamics on the surrounding beaches. The Colombo Harbor Expansion Project has created about 5-km-long breakwater nearly perpendicular to the beach. The present study is focused on quantitatively and qualitatively analyzing the effect of the Colombo Harbor Expansion Project on economically important beaches in and around Colombo city area. In this study, the authors measured monthly variations of beach width, beach profile and the mean grain-size of the sediments at mean sea level for complete annual monsoon cycle. Data were analyzed to establish site-specific erosion vulnerability. Monitoring results show that cumulative beach erosion has increased after the construction of the breakwater (rate = 0.7 m/year from May 2000 to April 2011 and rate = 28.2 m/year from April 2011 to June 2012). In addition, the cumulative and site-specific sand accretion and erosion patterns have a clear relationship with the monsoon seasonality. Beaches were narrower during the stormy southwestern monsoon, whereas beaches were wider during fair weather of northeast monsoon and inter-monsoon periods. In contrast, the constructed breakwater obstructs natural longshore sediment dynamics. For example, a significant amount of sediments from the Kelani-Ganga River were buried in the Colombo Harbor due to alteration of prominent longshore sediments transportation on the western coast of Sri Lanka. Therefore, this study shows enhancement of coastal erosion in the studied southern beaches due to a lack of sediment deposition. 相似文献
16.
With 60% of the world’s population living within the coastal zone, coastal erosion is considered as a global problem. The coasts of the Maltese Islands hold a variety of formations resulting from coastal erosion. Beach nourishment is one of the protective measures taken against coastal erosion. This paper focuses on two of the nourished beaches within the Maltese Islands, St George’s Bay (St Julians) and Pretty Bay (Birżebbuġa), that have undergone extensive sand augmentation during the past decades and looks at the extent of how coastal erosion and beach replenishment may have influenced public perception. Through a triangulation of interviews, it seeks to understand the views of beach users, researchers, representatives, and beach managers. It presents divergences in interviewee opinions and ideas on St George’s Bay and Pretty Bay and illustrates that public perception tends to reflect the type of urban area surrounding each replenished beach. Recommendations and suggestions are also presented to promote awareness towards coastal processes and their impacts.
相似文献17.
18.
The subaerial delta of the Yellow River has undergone a notable reshaping process with drastic changes in erosion and accretion patterns both temporally and spatially. These morphological changes not only have significant impact on the long-term evolution of delta but also pose severe threat to the existing infrastructures adjacent to the eroding delta lobe. This paper presents a data-based study of waves, currents, sediments and subaqueous bedforms including the application of Principal Component Analysis (PCA) to the measured coastal profiles in order to understand qualitative and quantitative processes that are responsible for the observed changes. The results demonstrated that the Yellow River Delta has recently been dominated by recession process due to the reduced sediment supply from the Yellow River in the recent decades. A critical threshold of river sediment discharge was formulated and used to explain the observed morphodynamic processes. It was found that the coast of the Yellow River Delta could be broadly divided into three geomorphic zones: the area near abandoned delta, the estuarine area, and Laizhou Bay. At the nearshore zone of the abandoned delta, waves are the main agent for bed erosion and sediments suspension. The tidal current is effective in transporting suspended sediments and exerts the main control on the depths of the erosion–accretion balance zone on the coastal profiles. The area near the present estuary has seen rapid deposition with the progradation rate being governed by the relative intensity of fluvial and marine processes while the coasts in Laizhou Bay are stable and the particular characteristics of the tidal current field prevent the sediments supplied by the Yellow River from reaching this area. 相似文献
19.
A. Di Matteo M. Milli Ph.D. 《International Journal of Environmental Science and Technology》2008,5(3):415-424
This paper outlines the results of a study recently carried out on the western coast of the Sestri Levante peninsula (Eastern Liguria-Italy), aiming to assess the effects of newly accomplished defensive measures against coastal erosion: the accretion of the beach with natural sand and its protection with artificial structures orthogonal and parallel to the shoreline. Through conventional and more innovative methodologies (respectively single beam echo sounders and global positioning system) the research work has resulted in a new evaluation of the morphological, bathymetric and sedimentological features that make up this shoreline and its volumetrical change over the century. The survey and the research carried out on the studied area have enabled us to give a more detailed picture of the evolution of the littoral, to assess the possible use of “non-traditional” techniques of beach development monitoring, to evaluate the volumetric variations of the emerged and submerged beaches, to establish the sedimentological activity of the beach after the latest nourishment measures, and finally, to verify the effectiveness of the protection measures implemented on this coastline. The acquired data have been stored in the database and a geographic information system has been used to process, analyze, and evaluate the results. The main findings show that the latest intervention has brought about a new phase in the evolution of the coastline, giving rise to a new pseudo-balanced condition. The re-distribution of materials used for the beach nourishment, leads us to believe that the defence underwater barrier has only partially worked. The main conclusion for a correct coastal zone management underline the necessity to plan local and more wide monitoring during at least 8–10 consecutive years. 相似文献
20.
Shipping activities in the Port of New York-New Jersey are currently threatened by restrictions on dredging of navigational channels and private berthing areas becaused of concerns about the environmental effects caused by ocean disposal of the dredged material. Current proposals for solutions to the problem include ocean disposal of uncontaminated material, use of confined disposal facilities (both upland facilities and containment islands), subaqueous barrow pits, and processing and treatment for contaminated materials. A project to produce a complete “treatment train” for processing and decontaminating dredged material is described. The work is divided into several phases: treatability studies of commercial and nonproprietary technologies at volumes of 19 liters (bench scale) and up to 19 m3 (pilot scale); specification of a treatment train; and implementation of a large-scale facility that can process 76,000–382,000 m3 of dredged material per year. The goal is to achieve operational status for the facility by the end of 1999. 相似文献