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1.
Anthony M. Foyle 《Environmental Earth Sciences》2014,71(10):4565-4578
Climate change in the Great Lakes Basin of North America over the next several decades is projected to lead to significant changes to coastal environments. Groundwater-driven coastal bluff recession should increase in areas where groundwater forcing is important and lead to increased loss of coastal uplands. The latter is an issue in NW Pennsylvania because of coastal development pressures, and because the state ranks within the top five US states in grape production, most of which occurs within 5 km of the Lake Erie coastline. In 2007, viticulture contributed almost $2.4 billion to the state economy. An analysis of a 20-km stretch of coast shows that bluff retreat is pervasive and variable under current climatic conditions. Over a 9-year time frame, bluff change rates ranged from ?4.2 to +0.98 m/year. In general, higher retreat rates (?0.2 to ?0.65 m/year) occurred along the sandy central beach–ridge sector which lacks significant surface drainage. Lower retreat rates (?0.10 to ?0.25 m/year) occurred along coastal sectors where surface drainage networks are well developed. Conservative estimates of groundwater discharge at the bluff correlate strongly (r = 0.74, p < 0.001) with bluff retreat rate. Groundwater is inferred to be the principal driving mechanism for both bluff retreat and spatial variability in retreat rates on this coast. Other common factors that may spatially influence bluff retreat elsewhere (bluff height, land use, beach width) do not correlate strongly with retreat rate. 相似文献
2.
Grace S. Brush 《Estuaries and Coasts》2009,32(1):18-28
Organisms and chemicals preserved in sediment cores from the Chesapeake estuary in mid-Atlantic USA are consistent with a
precolonial landscape covered with a diversity of forests and marshes, large and small. During the past 300 years, many of
the wetlands have been drained, and the landscape was converted to agricultural fields and urban and suburban development.
During this time, sources of nitrogen have diversified, and loadings have increased. Since precolonial time, the mesohaline
estuary has become increasingly eutrophic and anoxic. Estuaries and coastal regions throughout the world have experienced
similar conditions in their recent history. These changes are recorded in Chesapeake sediment cores by increases in ragweed
pollen, dry taxa, sedimentation rates, nitrogen influxes, and a major change in estuarine autotrophs from benthic to planktonic.
In many areas, attempts to reverse estuarine eutrophication and anoxia have centered on restoring streams and riparian areas
and reducing fertilizer use on agricultural lands. However, data from soils and historical reports and the paleoecological
record suggest that to reduce the effects of modern nitrogen inputs, it may be necessary to locate and enhance denitrifying
areas throughout the watershed. 相似文献
3.
A century of land subsidence in Ravenna, Italy 总被引：4，自引：2，他引：4
P. Teatini M. Ferronato G. Gambolati W. Bertoni M. Gonella 《Environmental Geology》2005,47(6):831-846
Over the last century the Ravenna area has been affected by a widespread land subsidence process of both natural and anthropogenic origin which has become a matter of increasingly great concern. Land settlement, initially of the order of a few mm/year, dramatically increased up to 110 mm/year after World War II primarily due to groundwater pumping and, subordinately, gas production from a number of deep on-shore and off-shore reservoirs. Spirit leveling was carried out in the area of the Ravenna Municipality by various authorities and agencies ever since the end of the nineteenth century using an increasingly refined network of benchmarks. The available information, spanning the time interval from 1897 to 2002, has been implemented and homogenized into a Geographic Information System (GIS). Measurements processed by kriging provide the pattern of the subsidence rates over the municipal territory during eight sub-periods. The reliability of data processing is discussed for both magnitude and areal distribution of the occurrence, showing a pronounced nonlinear behavior in time, as related to the major responsible factors. Cumulative land subsidence approaches almost 1 m over more than one third of the municipality area including the city and a significant fraction of the coastland, with peaks larger than 1.5 m over a 10 km2 zone located between the historical center and the coastline. Most recent records show that at present the mainland appears to be substantially stable, whereas some coastal areas are still subsiding at a rate of about 10 mm/year with a significant threat to the environment and the infrastructures as well, although to a lesser extent than in the past decades. 相似文献
4.
The estuarine environment can serve as either a source or sink of carbon relative to the coastal ocean carbon budget. A variety of time-dependent processes such as sedimentation, carbon supply, and productivity dictate how estuarine systems operate, and Mobile Bay is a system that has experienced both natural and anthropogenic perturbations that influenced depositional processes and carbon cycling. Sediments from eight box cores provide a record of change in bulk sediment accumulation and carbon burial over the past 110 years. Accumulation rates in the central part of the basin (0.09 g cm?2) were 60–80 % less than those observed at the head (0.361 g cm?2) and mouth (0.564 g cm?2) of the bay. Sediment accumulation in the central bay decreased during the past 90 years in response to both anthropogenic (causeway construction) and natural (tropical cyclones) perturbations. Sediment accumulation inevitably increased the residence time of organic carbon in the oxic zone, as observed in modeled remineralization rates, and reduced the overall carbon burial. Such observations highlight the critical balance among sediment accumulation, carbon remineralization, and carbon burial in dynamic coastal environments. Time-series analysis based solely on short-term observation would not capture the long-term effects of changes in sedimentation on carbon cycling. Identifying these relationships over longer timescales (multi-annual to decadal) will provide a far better evaluation of coastal ocean carbon budgets. 相似文献
5.
【研究目的】近20年来,长江三角洲海岸带地区土地类型结构发生显著转化,海岸带开发与保护的矛盾凸显。本文旨在开展长江三角洲海岸带典型区土地利用变化与生态环境效应研究,为海岸带地区的土地资源可持续利用、海岸带环境保护提供科学依据。【研究方法】利用美国Landsat卫星系列遥感影像和中国资源卫星系列遥感影像,采用自动监督分类并结合目视解译,获取了研究区1995—2015年共5期土地利用分类数据,分析土地利用变化特征和趋势,探讨长江三角洲海岸带典型区城镇发展、围填海时空变化及生态环境效应。【研究结果】长江三角洲海岸带典型区（南通、上海、嘉兴、宁波和舟山）1995年至2015年,土地利用变化明显,耕地大幅度减少,比例从1995年的68.8%降为2015年的55.7%;城镇建设用地迅速扩张,年平均增加192.8 km2。【结论】在快速城市化过程中,人口、单位面积能源消耗等快速增加,环境问题凸显,大量的耕地转为建设用地,围填海使滨海湿地面积快速减小和消失,导致CO2和污染物释放与吸收严重失衡,海洋环境受流域和沿海城镇化建设的影响明显,长江口及邻近海域近20年来赤潮频发,研究区陆域和海洋环境压力增加。创新点：选取长江三角洲海岸带典型区,首次以1995—2015年5期序列遥感影像数据为基础,采用空间叠加分析方法,着重分析了建设用地和围填海区域的时空演化特征;以人类活动为主线,综合多种海洋环境指标,分析快速城市化进程中,建设用地和围填海导致的生态环境效应。 相似文献
6.
D. Michael Williams 《Geoarchaeology》2004,19(2):167-175
Two massively constructed stone forts exist on the edge of vertical coastal cliffs on the Aran Islands, Ireland. One of these, Dun Aonghusa, contains evidence of occupation that predates the main construction phases of the walls and broadly spans a time interval of 3300–2800 yr B.P. The other fort, Dun Duchathair, has been termed a promontory fort because its remaining wall crosses the neck of a small promontory marginal to the cliffs. Estimates of past rates of marine erosion in this part of Ireland may be made both by analogy with studies in other areas and comparison with present day rates of marine erosion. A working model for erosion rates of approximately 0.4 m of coastal recession per annum is suggested. By applying this rate to the cliffs of the Aran Islands, it can be shown that, assuming a construction date of approximately 2500 yr B.P. for these forts, they were originally built at a considerable distance from the coastline. Thus Dun Duchathair was not a promontory fort. The earliest recorded habitation at Dun Aonghusa, dated to the middle of the Bronze Age, was, therefore, at some distance inland and not on an exposed 70 m high cliff on the edge of the Atlantic Ocean. © 2004 Wiley Periodicals, Inc. 相似文献
7.
中国沿海地质环境与区域持续发展的若干问题探讨 总被引：2，自引：1，他引：2
本文分析了中国沿海岩石圈动力学的基础特征, 指出中国东部沿海地质环境与灾害存在南北分异的格局, 阐述了沿海区域工程地质环境的基本规律, 并通过全球及中国近百年海平面变化, 以及人类工程活动对河口海岸地质环境影响的分析, 对沿海地区未来的地质环境与灾害趋向做了初步评估, 并认为中国沿海21世纪的环境与发展将面临严峻的挑战, 特别是环渤海地区。最后, 对影响沿海区域发展的若干问题进行了初步探讨并提出了几点建议。 相似文献
8.
Climate change-induced extreme weather events have been at their worst increase in the past decade (2010–2020) across Africa and globally. This has proved disruptive to global socio-economic activities. One of the challenges that has been faced in this regard is the increased coastal flooding of cities. This study examined the trends and impacts of coastal flooding in the Western Cape province of South Africa. Making use of archival climate data and primary data from key informants and field observations, it emerged that there is a statistically significant increase in the frequency of flooding and consequent human and economic losses from such in the coastal cities of the province. Flooding in urban areas of the Western Cape is a factor of human and natural factors ranging from extreme rainfall, usually caused by persistent cut off-lows, midlatitude cyclones, cold fronts and intense storms. Such floods become compounded by poor drainage caused by vegetative overgrowth on waterways and land pollution that can be traced to poor drainage maintenance. Clogging of waterways and drainage systems enhances the risk of flooding. Increased urbanisation, overpopulation in some areas and non-adherence to environmental laws results in both the affluent and poor settling on vulnerable ecosystems. These include coastal areas, estuaries, and waterways, and this worsens the risk of flooding. The study recommends a comprehensive approach to deal with factors that increase the risk of flooding as informed by the provisions of both the Sustainable Development Goals framework and the Sendai Framework for Disaster Risk Reduction 2015–2030 in a bid to de-risking human settlement in South Africa.
相似文献9.
Human impact has increased stunningly during the last century with coastal problems being one manifestation of environmental injustice with ecological, economic, and social dimensions on coastal resources. The study sought to assess the residents’ perception of coastline changes in the milieu of the rampant sand mining activities along the Elmina, Cape Coast and Moree coastline of Ghana. The study employed the purposive sampling technique: 100 respondents were engaged from the selected study areas through simple random sampling method. Interviews, Focus group discussions, observations and questionnaire were the main instruments used. The study revealed that beach sand mining is widespread across the Elmina-Cape Coast-Moree coastline and takes place in several forms, with the magnitude of sand taken from the beach being dependent on the transportation medium and the purpose to which sand is to be put. It is considered that the 1995 National Environmental Policy has become outdated and the sections dedicated to the coastal zone are irrelevant due to new research data and trends in administration. The time is right for a concerted national policy dedicated to only the coastal zone that takes into consideration the multiplicity of use of the zone and adopts an integrated management approach. 相似文献
10.
Rapid development of shrimp farming may lead to unrecognized and undesirable changes of land cover/land use patterns in coastal areas. Of special concern is the loss of mangrove forest in coastal areas such as Quang Ninh, Vietnam, which is adjacent to the World Heritage-listed Ha Long Bay. Understanding the status and changes of land cover/land use for coastal shrimp farms and mangrove forests can support environmental protection and decision-making for sustainable development in coastal areas. Within this context, this paper uses the 1999/2001 Landsat ETM+ and the 2008 ALOS AVNIR-2 imagery to investigate the contraction and expansion of shrimp farms and mangrove forests in coastal areas of Ha Long and Mong Cai, which now have a high concentration of intensive and semi-intensive shrimp farms. Images were separately analyzed and classified before using post-classification comparisons to detect land cover/land use changes in the study area. The results of this study found that the area of mangrove forest has been reduced by an estimated 927.5 ha in Ha Long and 1,144.4 ha in Mong Cai, while shrimp farming areas increased by an estimated 1,195.9 and 1,702.5 ha, respectively, over the same period. The majority of shrimp farms in Mong Cai were established at the expense of mangrove forest (49.4 %) while shrimp farms in Ha Long were mainly constructed on areas previously occupied by bare ground (46.5 %) and a significant proportion also replaced mangroves (23.9 %). The remarkable rate of mangrove loss and shrimp farming expansion detected in this study, over a relatively short time scale indicate that greater awareness of environmental impacts of shrimp farm expansion is required if this industry is to be sustainable, the important estuarine and coastal marine ecosystems are to be protected over the long term, and the capturing and storing of carbon in mangrove systems are to be enhanced for global climate change mitigation and for use as carbon offsets. 相似文献
11.
Changes of freshwater-lens thickness in basaltic island aquifers overlain by thick coastal sediments 总被引：1，自引：1，他引：0
Freshwater-lens thickness and long-term changes in freshwater volume in coastal aquifers are commonly assessed through repeated measurement of salinity profiles from monitor wells that penetrate into underlying salt water. In Hawaii, the thickest measured freshwater lens is currently 262 m in dike-free, volcanic-rock aquifers that are overlain by thick coastal sediments. The midpoint depth (depth where salinity is 50% salt water) between freshwater and salt water can serve as an indicator for freshwater thickness. Most measured midpoints have risen over the past 40 years, indicating a shrinking lens. The mean rate of rise of the midpoint from 1999–2009 varied locally, with faster rates in highly developed areas (1.0 m/year) and slower rates in less developed areas (0.5 m/year). The thinning of the freshwater lenses is the result of long-term groundwater withdrawal and reduced recharge. Freshwater/salt-water interface locations predicted from measured water levels and the Ghyben-Herzberg principle may be deeper than measured midpoints during some periods and shallower during other periods, although depths may differ up to 100 m in some cases. Moreover, changes in the midpoint are slower than changes in water level. Thus, water levels may not be a reliable indicator of the amount of freshwater in a coastal aquifer. 相似文献
12.
Coastal cliff erosion is a problem in many coastal areas. However, often only very limited data are available to quantify the rates of recession for the development of coastal management strategies. In the soft flysch deposits of the Waitemata Group, Auckland, New Zealand, coastal cliffs are associated with shore platforms. Two models exist for the profile evolution of shore platforms and associated cliffs: the first suggests that an equilibrium profile develops in response to erosive processes, and this profile subsequently migrates landward; the second model suggests that the seaward margin of the shore platform is relatively static, and the profile extends landward through a combination of cliff recession and platform lowering. Physical simulations and field measurements for mudstone and limestone lithologies indicate that the second model is more likely for soft flysch deposits. A eustatic sea-level curve for the Weiti Estuary, Auckland, suggests that up to 7120 ± 70 years have been available for shore platform development since sea level reached the present seaward margins of shore platforms. Shore platform widths were measured using GPS at two sites in Waitemata Group rocks: the North Shore of Auckland; and the southern side of the Tawharanui Peninsula, North Auckland. The long-term cliff recession rates estimated from shore platform widths (1.4 ± 0.1 to 14.3 ± 0.1 mm y− 1) are consistent with the lower end of the average range of cliff top and face recession rates published for Waitemata Group rocks using different methods (11–75 mm y− 1), and in agreement with cliff base recession estimates (3.5 mm y− 1). Shore platform widths were qualitatively related to the rock mass characteristics of the associated cliffs, and therefore platform widths could provide a method of identifying regions of potential hazard. 相似文献
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14.
What roles have human impacts and natural processes had in shaping the evolution of Mediterranean coastlines during the Holocene? Where, when and how did societies transform the coastal zone? At what scales and rhythms did these changes take place? What can ancient harbour sediments tell us about human‐environment interactions? During the past 20 years, geoarchaeological research in the Mediterranean has attempted to understand the interplay between culture and nature, and more particularly how environments and processes have played a role in Holocene human occupation of the coastal zone. This approach has drawn on the multidisciplinary study of sediments, as archives of information, to attempt to differentiate between anthropogenic and natural factors, the latter, we argue, having played an increasingly secondary role with time. Three important spatial scales of analysis have emerged, local, regional and Mediterranean, all of which are outlined here. 相似文献
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16.
Stratigraphy and sedimentology of the Upper Cretaceous to Paleogene Kilwa Group, southern coastal Tanzania 总被引：2，自引：0，他引：2
Christopher J. Nicholas Paul N. Pearson Paul R. Bown Tom Dunkley Jones Brian T. Huber Amina Karega Jackie A. Lees Ian K. McMillan Aoife O&#x;Halloran Joyce M. Singano Bridget S. Wade 《Journal of African Earth Sciences》2006,45(4-5):431-466
The geology of southern coastal Tanzania has remained poorly understood since the first comments on its stratigraphy were made over 100 years ago. However, new field surveys combined with shallow drilling along the coast between Kilwa and Lindi are beginning to resolve the depositional history and structural evolution of this region over the past 85 Ma. Here we present the first attempt to synthesize the results of these studies to provide a coherent sedimentological, litho- and sequence stratigraphic framework, including new geological maps, for the Upper Cretaceous and Paleogene of the coastal zone.Santonian to Oligocene sediments crop out along a broad coastal belt south of the Rufiji River from the Kilwa peninsula to Lindi Creek in southern Tanzania. During 55 Ma, over 1 km of a broadly homogeneous, mid to outer shelf clay-dominated succession was deposited across the passive margin, which we define here as the Kilwa Group. This lies disconformably across the shelf on Albian marls and is itself unconformably overlain by shallow water Miocene clays and more recent limestones, sands and gravels. Four formations can be identified within the Kilwa Group on the basis of characteristic secondary lithologies and facies, described here for the first time; the Nangurukuru, Kivinje, Masoko and Pande Formations. These formations include conformable stratigraphic intervals through both the Paleocene–Eocene and Eocene–Oligocene boundaries. Within the Kilwa Group, 12 sequence stratigraphic cycles can be identified at present, demonstrating relatively uniform and continual subsidence across the margin from Santonian to Early Oligocene time. A further major bounding surface is present between the Upper Cretaceous and Paleogene, but this may become partly conformable in the Lindi area. Although the principal lithology in all formations is clay or claystone, there are more permeable intervals containing pervasive coarser siliciclastic sediments and these have yielded traces of crude oil which is likely to have migrated from lower in the succession. The Kilwa Group thus also provides important new evidence for petroleum play development in the southern coastal zone. 相似文献
17.
Characteristics of Beachrocks: A Review 总被引：1，自引：0，他引：1
Beachrocks are calcareous rocks that have been quite recently formed and are found in the intertidal zone on sandy beaches. The authors are developing an artificial rock with self-healing capabilities that can be used in coastal areas to repair the infrastructure of coastal walls. Because beachrocks are formed naturally on beaches, they merit study as a model for artificial rocks. We conducted a bibliographical study in order to gather information about the characteristics of beachrocks, which may aid in the manufacturing of artificial rocks. This study investigated their geographic distribution, formative periods, physical properties, and origins. The study found that over 90 % of beachrocks are found between the latitudes 40°N and the Tropic of Capricorn, and that their formative periods range from 26,000 years to just a few decades ago. We also learned that the cement component of beachrocks mainly consists of either calcium carbonate or silica. The dynamic characteristics of these components have been studied in only three papers, which note that their uniaxial compression strength ranges from as low as 6.0 to 42.0 MPa. Since very limited data are available on beachrocks in Japan where the artificial rock technology will first be deployed, there is a need for collecting additional data on their mechanical properties, elemental composition ratios, and mineral content. 相似文献
18.
This Special Issue deals with the impact of climate change on western European coastal systems. Notwithstanding the inherent problems of studying geological data in terms of climate shifts, the results show that on the meso- and the macroscale of time, climatic forcing is a major drive for coastal change. However, its impact is largely influenced by other factors. Sediment availability plays a dominant role in the evolution of coastal systems and it can be considered one of the most important thresholds at the land-ocean interface. Sea-level changes are expected to have a significant impact on most European coasts. There is particular concern for the tidally influenced flats and marshes, and for those coastal areas known to have already a net sediment deficit and to be threatened by erosion. Areas where isostatic uplift has countered sea-level rise until now, are expected to become subject to coastal erosion in the near future under an accelerated sea-level rise scenario. The sensitivity and vulnerability of coastal systems to climate shifts is shown to be largely controlled by storm magnitude and fetch. A particular case of vulnerability is the impact of tsunamis. Finally, the consequences of human interference have been demonstrated in many cases. The implementation of geoscientific studies for rational, comprehensive and cost-effective strategies on a regional or national level of integrated coastal zone management is reviewed. 相似文献
19.
海岸带位于海陆交互地带,其独特的地理、地质和环境条件导致其灾害地质现象发育,地质灾害易发性和危险性高。考虑到海岸带的重要经济和社会属性,开展海岸带的地质灾害风险评价显得极为重要。本文首先建立了基于模糊贝叶斯网络的地质灾害风险评价模型,结合网络层次分析法(ANP)确定模糊贝叶斯网络的条件概率,并简化了贝叶斯网络的结构图谱。在此基础上,以辽东半岛东部海岸带作为研究区,以崩塌、滑坡、地面塌陷、海岸侵蚀和海水入侵等5个主要地质灾害类型作为评价对象,开展了基于ANP-模糊贝叶斯网络模型的地质灾害易发性、危险性和风险性评价,并编制了综合地质灾害风险分布图;结果显示,区内高、较高风险区主要分布于研究区的西南部海岸带,面积为249km2,约占全区面积的9.1%。研究成果可为海岸带国土资源开发、经济建设规划、防灾减灾救灾等提供重要参考,对同类地区的海岸带地质灾害风险评价具有一定借鉴意义。 相似文献
20.
Coastal plains are amongst the most densely populated areas in the world. Many coastal peatlands are drained to create arable land. This is not without consequences; physical compaction of peat and its degradation by oxidation lead to subsidence, and oxidation also leads to emissions of carbon dioxide (CO2). This study complements existing studies by quantifying total land subsidence and associated CO2 respiration over the past millennium in the Dutch coastal peatlands, to gain insight into the consequences of cultivating coastal peatlands over longer timescales. Results show that the peat volume loss was 19.8 km3, which lowered the Dutch coastal plain by 1.9 m on average, bringing most of it below sea level. At least 66 % of the volume reduction is the result of drainage, and 34 % was caused by the excavation and subsequent combustion of peat. The associated CO2 respiration is equivalent to a global atmospheric CO2 concentration increase of ~0.39 ppmv. Cultivation of coastal peatlands can turn a carbon sink into a carbon source. If the path taken by the Dutch would be followed worldwide, there will be double trouble: globally significant carbon emissions and increased flood risk in a globally important human habitat. The effects would be larger than the historic ones because most of the cumulative Dutch subsidence and peat loss was accomplished with much less efficient techniques than those available now. 相似文献