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1.
The coastal zone of northwest Portugal can be subdivided into two geomorphological sectors: Sector 1, between the Minho River and the town of Espinho, where the coastal segments consist of estuaries, sandy and shingle beaches with rocky outcrops, and Holocene dune systems (foredunes and some migrating dunes with blow-outs). The estuaries and the foredunes in particular are very degraded by human activities. Sector 2, between Espinho and the Mondego Cape, where coastal lagoons and Holocene dune systems (foredunes, parabolic and transverse dunes) occur. This study deals with the macroscale, i.e. 100–1000 years, forcing by sea-level changes and neotectonic activity on the one hand, and mesoscale, i.e. 1–100 years, forcing by climate fluctuations on the other hand, on these (palaeo-)environments. It is shown in particular that sea-level changes and neotectonic activity play a dominant role in the evolution of the coastal zone since the Late Pleistocene. Sediment starvation on the shoreface is postulated to be one of the major causes for coastal erosion since at least the 15th century. The mesoscale role of climate is difficult to assess at the present stage of knowledge, mainly because of overprinting by the macroscale evolution of the coast. However, data on estuarine saltmarsh evolution in sector 1 point towards discrete changes in storminess, while the development of Medieval dune systems in sectors 1 and 2 are attributed to the Little Ice Age or, alternatively, to human occupation of the dune areas. 相似文献
2.
利用历史文献记录重建了公元1000—2000年中国北方地区极端干旱事件序列,在此基础上分析极端干旱事件的发生特征与规律。研究得出以下结论:(1)极端干旱事件在公元1000—2000年中存在200年左右的周期波动。在15世纪中期、17世纪初期和18世纪末期存在3次极端干旱事件高发期。(2)极端干旱事件的变动与中国东部地区干湿变化相一致,在偏干的时期极端干旱事件发生次数上升,在偏湿时则下降。(3)在中世纪暖期和现代暖期,温度愈高,极端干旱事件偏多;而在小冰期,则温度偏低的时期极端干旱事件多发。(4)西风带影响下的非季风区,干湿变化与极端干旱事件的关系与华北季风区相反,这可能与所谓的“丝绸之路遥相关”和NAO(NorthAtlanticOscillation,北大西洋涛动)的影响有关。 相似文献
3.
Prof. Dr Mei-e Ren 《GeoJournal》1992,28(4):443-448
Man is an important geological agent. This paper documents a unique case of the dominating role of man in coastal evolution and hydrological changes in North Jiangsu province. Owing to human breaching of dikes on the Lower Yellow River in 1128, a large anthropogenic delta — the Abandoned Yellow River Delta was formed. Its rapid growth and quick decay over a period of 400 years further illustrates the overwhelming influence of human activity in triggering coastal changes. Man's diversion of the Yellow River to Jiangsu has also resulted in a dramatic change of the drainage pattern and hydrology of North Jiagsu. The Huai-He, a major river in central China, was changed from an independent river draining into the sea in the 11th century, to a tributary of the Yangtze river since the 17th century. At the same time, Hongze lake was enlarged from a small lake to one of the largest fresh water lakes in the country. 相似文献
4.
Oya Algan M. Nam?k Yalç?n Yücel Y?lmaz Elmas K?rc?-Elmas Özlem Bulkan Cem Gazio?lu Mehmet Ali Polat 《Quaternary Research》2011,76(1):30-45
An extensive rescue excavation has been conducted in the ancient harbor of ?stanbul (Yenikap?) by the Sea of Marmara, revealing a depositional sequence displaying clear evidence of transgression and coastal progradation during the Holocene. The basal layer of this sequence lies at 6 m below the present sea level and contains remains of a Neolithic settlement known to have been present in the area, indicating that the sea level at ~ 8-9 cal ka BP was lower than 6 m below present. Sea level advanced to its maximum at ~ 6.8-7 cal ka BP, drowning Lykos Stream and forming an inlet at its mouth. After ~ 3 cal ka BP, coastal progradation became evident. Subsequent construction of the Byzantine Harbor (Theodosius; 4th century AD) created a restricted small basin and accumulation of fine-grained sediments. The sedimentation rate was increased due to coastal progradation and anthropogenic factors during the deposition of coarse-grained sediments at the upper parts of the sequence (7th-9th centuries AD). The harbor was probably abandoned after the 11th century AD by filling up with Lykos Stream detritus and continued seaward migration of the coastline. 相似文献
5.
Coastal flood risks and seasonal tourism: analysing the effects of tourism dynamics on casualty calculations 总被引：1，自引：1，他引：0
Wim Kellens Tijs Neutens Pieter Deckers Johan Reyns Philippe De Maeyer 《Natural Hazards》2012,60(3):1211-1229
Since coastal tourism is one of the fastest growing sectors of tourism industry, coastal areas have become increasingly vulnerable
in the case of flooding. While in recent years a number of different methods have been put forward to map coastal flood risks,
the implications of tourism dynamics for the assessment of human casualties has remained largely overlooked in these models.
This chapter examines to what extent the ignorance of (residential) coastal tourism may bias the calculations of human casualties.
To this end, a case study has been conducted on the Belgian coast. Both the dynamic nature of coastal tourism and the behaviour
of residential tourists in storm surge scenarios are considered. The results of this study show that including tourism dynamics
in flood risk management is justified and appropriate, depending on the tourist attractiveness of the flood-prone area and
its temporal fluctuations. 相似文献
6.
Land, Sea and Human Effort was the central theme of the 28th IGU Congress in The Hague, The Netherlands. This volume contains the key-note addresses highlighting this central theme. Three major issues regarding low-land coasts came to the fore: land-use, environmental quality and safeguarding of the land. An interesting question is whether the concentration of human activities in large urban nodes will continue, or that such nodes and hierarchies will no longer structure our world, because of the ever-increasing importance of all means of communication and transport, as indicated by Johnston. Functions may disperse to specialised environments. A similar specialisation may be encountered in e.g. the development of tourism in the coastal zone. As Gormsen has elucidated, tourism has over time extended in a sequence of spatial peripheries. Consequently, phases in development may be identified with a growing impact and participation of local tourism interwoven with international growth. The environmental quality of coastal zones is seriously under threat, due to ever-increasing population pressure and human exploitation. The major problems are pollution and the availability of good quality water. Oudshoorn explored the worlds resources of drinking water, indicating the great need for political awareness of this huge problem. Cross-sectoral planning is advocated by Oudshoorn, even if water management often trespasses international boundaries and the harmonisation of the planning strategies is mostly difficult. The environmental quality of the coastal zone is also affected by the exploitation of oil and gas resources. Odell demonstrates that the conditions for this exploitation in the North Sea are unique, especially because of the great impact of an international agreement on offshore exploitation. Planning in sea areas is becoming an issue of increasing importance as it has to cope with the many, often conflicting interests, such as shipping, fishery, mining, waste disposal in relation to environmental and ecological constraints. The safeguarding of the land against river floods and sea side storm surges under the threat of a rising sea level is another important issue in coastal low-lands. Callander reviews the present state of human influence on climatic change and the associated sea level change. As indicated by Hesselman et al. new remote sensing and associated GIS techniques have recently been developed which are a great contribution in determining the fate of the coastal zones with respect to the threats induced by natural and human activities. 相似文献
7.
M. Antonellini T. Dentinho A. Khattabi E. Masson P. N. Mollema V. Silva P. Silveira 《Environmental Earth Sciences》2014,71(4):1839-1853
The assessment of freshwater resources in a drainage basin is not only dependent on its hydrologic parameters but also on the socio-economic system driving development in the watershed area; the socio-economic aspect, that is often neglected in hydrologic studies, is one of the novelties of this study. The aim of this paper is twofold: (1) presenting an integrated working methodology and (2) studying a local case of a North African watershed where scarce field data are available. Using this integrated methodology, the effects of climate and land use change on the water resources and the economic development of the Tahadart drainage basin in Northern Morocco have been evaluated. Water salinization, tourism, urbanization, and water withdrawals are a threat to water resources that will increase with future climate change. The Tahadart Basin (Morocco 1,145 km2) is characterized by rain-fed agriculture and by the presence of two water retention basins. Assessment of the effects of climate and land use change on this drainage basin was based on current and future land cover maps obtained from spatial interactions models, climate data (current and future; scenario A1b for the period 2080–2100), and hydrological models for water budget calculations. Land use suitability maps were designed assuming a A1b Special Report on Emissions Scenarios socio-economic development scenario. The most important conclusions for the period 2080–2100 are the following: (1) Freshwater availability within the watershed will likely be affected by a strong increase in evaporation from open water surface bodies due to increased temperature. This increase in evaporation will limit the amount of freshwater that can be stored in the surface reservoirs. (2) Sea level rise will cause flooding and salinization of the coastal area. (3) The risk for drought in winter is likely to increase. The methodology used in this paper is integrated into a decision support tool that is used to quantify change in land use and water resources. 相似文献
8.
三峡大坝建成后长江输沙量的减少及其对长江三角洲的影响 总被引：19，自引：6，他引：13
三峡大坝建成之后,大量泥沙滞留于库区,出库泥沙量减少,坝下河床冲刷而提供相当数量的泥沙,支流湖泊供沙也发生变化,这将使进入河口地区的泥沙有所减少。三峡大坝以上长江干流和支流建设新的大坝,南水北调、封山育林、退耕还林以及减少水土流失都将进一步减少长江进入河口地区的泥沙。由此估计,三峡大坝建成后的百年内长江输入河口地区的泥沙约为2.0×108～2.5×108t/a;冰后期长江三角洲形成和发育期间的长江年均输沙量为1.84×108～2.28×108t。二者的数值相当接近,然而与近50年的观测(4.33×108t/a)相差甚远,长江流域的气候变化和人类活动可能是造成这一现象的原因。文章着重说明中国和长江上游人口的增长、种植作物的改变可能是水土流失、长江泥沙量增长的主要原因。 相似文献
9.
Winter climatic anomalies in the North Pacific sector and western North America are statistically calibrated with tree-ring data in western North America and reconstructed back to AD 1700. The results are verified using climatic data from the last half of the 19th century, which is prior to the calibration period. Climatic conditions reconstructed for 18th and 19th century winters are then summarized and compared with the 20th century record. 相似文献
10.
中国21世纪若干重大工程地质与环境问题 总被引：11，自引：5，他引：11
21世纪中国的大规模的国家建设不可避免地导致大量的工程地质与环境问题。 2 1世纪中国西部高山峡谷地区主要工程地质问题有: 构造活动带岩土体动力稳定性, 高地应力下岩体应变储能与岩体性质, 高陡边坡的变形及尺寸效应和动力稳定性, 深埋长大隧洞的地温与地压, 深埋隧洞岩体结构探测与施工地质超前预报, 大跨度复杂洞群变形与稳定性的群洞效应, 冻土的冻融变形、稳定性及其处理技术, 可溶岩岩溶规律与岩体利用问题, 河床深厚覆盖层的处理与利用等问题; 中国东部及沿海地区工程地质问题包括: 高速交通网建设中软土地基变形与稳定性及处理技术, 深井采矿中软岩巷道大变形与处理技术, 深厚松散堆积层上大型桥梁桥基变形与稳定性, 海底隧道围岩工程地质与水文地质问题, 城市多层地下空间开发中的工程地质问题等; 此外, 水土流失与北方大规模荒漠化问题, 黄河下游地上悬河与长江下游塌岸和堤防稳定性问题, 黄河断流引起的下游地区环境问题, 我国北方干旱地区水资源长期匮乏问题, 城市化中的环境破坏与污染控制等问题, 将是中国 2 1世纪突出的环境问题。中国工程地质工作者应当在结构土力学与岩体结构力学、工程地质学的基本理论与工程地质动力学、人 地相互作用机制与环境工程地质学、地质工程理论与方法。 相似文献
11.
三峡大坝建成后长江输沙量的减少及其对长江三角洲的影响 总被引：3，自引：1，他引：3
三峡大坝建成之后,大量泥沙滞留于库区,出库泥沙量减少,坝下河床冲刷而提供相当数量的泥沙,支流湖泊供沙也发生变化,这将使进入河口地区的泥沙有所减少。三峡大坝以上长江干流和支流建设新的大坝,南水北调、封山育林、退耕还林以及减少水土流失都将进一步减少长江进入河口地区的泥沙。由此估计,三峡大坝建成后的百年内长江输入河口地区的泥沙约为2.0×108～2.5×108t/a;冰后期长江三角洲形成和发育期间的长江年均输沙量为1.84×108～2.28×108t。二者的数值相当接近,然而与近50年的观测(4.33×108t/a)相差甚远,长江流域的气候变化和人类活动可能是造成这一现象的原因。文章着重说明中国和长江上游人口的增长、种植作物的改变可能是水土流失、长江泥沙量增长的主要原因。 相似文献
12.
Two to three thousand years ago, the fringing tidal salt marsh wetlands (including brackish and freshwater marsh) of the Delaware coastal zone were three to four times wider than at present. Observed variations in rates of marsh surface aggradation suggest that some areas are undergoing inundation whereas many other areas are undergoing aggradation at rates greater than sea-level rise as measured by a local tidal gauge (average 33 cm/ century based on a 70-year record) and may be undergoing floral succession. Accompanying these sedimentary processes are coastal erosion rates up to 6.9 m/yr along the Delaware estuary, up to 2.8 m/yr along the Delaware Atlantic coast, and ranging from 0.1 m/yr to 0.6 m/yr along the Delaware Atlantic coastal lagoons. Human development has destroyed nearly 9% of Delaware's fringing salt marshes between 1938 and 1975. The rapidly growing trend toward hardening the edge of the adjacent landward uplands leads us to the conclusion that much of the fringing salt marsh of Delaware will disappear over the next two to three centuries with only small remnants declining to extinction ca. 1500–1700 years into the future. Impacts on the State of Delaware, comprised of 13% fringing salt marshes 1/4 century ago, will be profound in terms of destruction of a large segment of the Atlantic coastal or eastern North American migratory bird flyway, and an eventual forced accommodation of the inhabitants of Delaware to these naturally ongoing geological processes. 相似文献
13.
Large earthquakes and the abandonment of prehistoric coastal settlements in 15th century New Zealand
This paper reports on the effects of large earthquakes and related events, such as tsunamis, on prehistoric coastal settlements in New Zealand. It is based on field observations at several well‐established archaeological sites around the Cook Strait region and on literature reviews. We identify three broad periods of seismic activity in New Zealand since human occupation of the islands: 13th century, 15th century, and the 1750s to 1850s. The most significant, from a prehistoric human perspective, is the 15th century. Using examples from the Cook Strait region, we suggest that the abandonment of coastal settlements, the movement of people from the coast to inland areas, and a shift in settlement location from sheltered coastal bays to exposed headlands, was due to seismic activity, including tsunamis. We expect similar patterns to have occurred in other parts of New Zealand, and other coastal areas of the world with longer occupation histories. © 2003 Wiley Periodicals, Inc. 相似文献
14.
20世纪地球物理学的重要成就和21世纪的发展前沿 总被引：16，自引：1，他引：16
20世纪是地球物理学取得辉煌成就的重要历史时期。在这关键性的百年里实施了一系列大型且具全球性的研究计划。 2 1世纪必将在对地球本体的认识和解决水资源、矿产资源、自然灾害和环境 (包括空间环境 )方面继续作出新的重大贡献。只有深入研究地球内部物质与能量的交换 ,不同圈层的耦合及其深部动力过程才能深入探索地球系统的发展。为此 ,文中讨论三方面的问题 :(1)地球物理学的发展进程及其战略意义 ;(2 ) 2 0世纪地球物理学领域主要的重大成就 ;(3) 2 1世纪上、中叶地球物理学的发展前沿和导向。 相似文献
15.
The capital of the Democratic People’s Republic of Korea (North Korea) is both the oldest and the newest settlement in Korea. The basic concepts in its early urban development made it the model for Korean cities of later ages. In the 6th and 7th century AD P’yôngyang was one of the largest cities in Asia, second only to the imperial capital of China, but it later declined. It partly recovered its former position when it became the capital of North Korea after World War II. Its reconstruction since the Korean War has made it one of the most striking examples of socialist city planning. 相似文献
16.
Horst Meesenburg 《GeoJournal》1996,39(2):143-151
This article describes the influence of man on the coastal landscapes along the Danish and part of the German west coast. While the tidal coast south of Blåvandshuk was formed by man since premedieval times, the northern part of Jutlands coast nearly avoided human influence until the late 19th century when dune plantation and coast protection was begun. At the same time, the first harbours were built by the Danish state, mainly for fishing purposes. The human influence increased through the 20th century, with tourism as a main factor. The article highlights the radical changes and the fragile balance between human action and natural processes on a debris coast. The article summarizes some of the authors contributions in the Danish landscape magazine Bygd, of which he is editor. 相似文献
17.
18.
As an important carbon pool and fragile eco-system of earth system, more and more coastal saltmarshes have been reclaimed for releasing population pressure and promoting food safety and economic development, especially in developing countries. During reclamation, original soil carbon cycling pattern and pathway in saltmarshs would be changed, which furthermore could change global carbon budget. In this study, a great amounts of literature and data were summerized to generalize the changes of soil organic carbon, carbon sequestration rate and carbon flux in three main kinds of saltmarshes (Mangrove saltmarsh, Estuary saltmarsh and coastal saltmarsh) during reclamation. The results are as shown: ①The conclusions collected from Europe and America are not suitable to eastern Asia’s coast and more attention should be paid to eastern Asia’s coastal reclamation; ②Mangrove saltmarshes have higher Soil Organic Carbon (SOC) and carbon sequestration rate, followed by estuary saltmarshes and coastal saltmarshes. Soil clay, aggregate, burial rate usually have positive effect on SOC sequestration in coastal areas. Flood frequency, salinity and underground water level generally have negative effect on it. After reclamation, coastal SOC first shows a decrease followed by an increase. Nearly 30 years of reclamation is the turning point where paddy fields can significantly promote SOC; ③CH4 and CO2 are the main ways of carbon emission in coastal areas of which CO2 flux usually is the largest. Mangrove saltmarshes’ carbon emissions are the highest. In natural sites, the carbon emissions in Spartina alterniflora Loisel. and Phragmites australis are higher than those in bare flat areas. Carbon fluxes in flood tide usually are lower than those in other periods. Otherwise, carbon fluxes in natural saltmarshes are far lower than those in reclamation zones, especially upland tillage zones. The results acquired from field monitoring, saltmarshes are the carbon sinks and become the carbon sources when reclamation activities happen. Finally, three main aspects of coastal study were given as follows: much more attention should be paid to carbon budget inventory in saltmarshes; the effect of reclamation activity (i.e., anthropogenic activity, tillage practice, land use, etc.) on carbon cycling in ocean-inland system; the study of land use and reclamation process simulation and its impact on carbon cycling in coastal zone should be strengthened. 相似文献
19.
Data on glacier, tree-line, tree-ring, pollen, and ice-core variations in North America, Greenland, and Europe during the last 2000 yr (up to A.D. 1800) are compared in detail on the century time scale. Only data that may be indicative of summer temperature changes are included, since these comprise most of the available paleoclimatic information, although some variations (especially of glaciers) may have been in response to precipitation changes instead. Radiocarbon dates and 14C-dated records are converted to calendar (dendrochronological) years using the calibration of M. Stuiver (1982, Radiocarbon 24, 1–26). Despite the basic uncertainties in dating, interpretation, response times, and “noise level” of proxy climatic data, there is at times good agreement among different kinds of evidence from within a region to suggest an episode of generally warmer or cooler summers. Three previously identified episodes find expression in records from all of the regions considered: the “Little Ice Age” of the last few centuries, a “Medieval Warm Period” around the 12th century A.D., and an earlier cold period some time between the 8th and 10th centuries. However, the timing of minima and maxima within these episodes seems to have varied from region to region (although the evidence is consistent within regions). In the 15th century, summers were warm in the eastern Canadian Arctic and southern Greenland while there was a cold episode in Europe and western North America. 相似文献
20.
Records of massive fish kills and paralytic shellfish poisoning (PSP) in Europe and North America go back to the 17th century. But, it was not until the 1940s when the relationship between PSP, red tide and toxic dinoflagellateGonyaulax was established. Recent records show that PSP and related poisons caused by toxic dinoflagellates in coastal waters and estuaries, are a world-wide problem. Diarrhetic shellfish poisoning (DSP) and neurotoxic poisoning (NSP), believed earlier as bacterial or viral infections are now shown to be caused by other toxic dinoflagellates such asDinophysis. The shellfish most often involved in the poisoning are mussels and clams. Other dinoflagellates,Gyrodinium, occasionally cause massive fish kills in vast coastal areas, resulting in fishery and economic losses.Factors promoting toxic dinoflagellate bloom development and PSP/DSP outbreaks are not fully understood. In previous studies, temperature was considered as the principal factor influencing dinoflagellate blooming. Recent studies showed that other factors such as salinity, sunlight, freshwater runoff and water stability are also important. Pollution from land drainage and sewage discharge in inshore waters were also implicated.Current knowledge indicates that although chemical and biotic factors are important forin-situ growth of dinoflagellate cells, convergence by thermal and tidal fronts is essential for cell accumulation and bloom development. Advances in physical oceanographic research, modelling and remote sensing enabled the detection of fronts and bordering eddies with high precision. There is a potential for an increased use of these technological advances in predicting and monitoring the bloom development.The present paper overviews the history and distribution of toxic dinoflagellates, and the physical factors influencing bloom development and PSP/DSP outbreaks. Future research needs to improve the predictability and control of this world-wide hazard are also discussed. 相似文献