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1.
海岸带是陆地向海洋延伸的过渡地带,是人口最为密集、人类活动最频繁的区域,全球超过50%的人口和60%的GDP总量集聚在离海岸线不足100 km的区域。海岸线对海平面上升、海岸侵蚀、港湾淤积、湿地生态资源、近海海域环境等具有重要的指示作用。本研究利用遥感影像获取了粤港澳大湾区（以下简称大湾区）1975—2018年间的大陆海岸线数据,并基于GIS平台,对海岸线开发利用程度以及空间位置变迁进行了定量分析,探讨了海岸线变迁的驱动力。结果表明：（1）大湾区大陆岸线时空变化明显,总体可分为两个阶段。1975—1995年,岸线长度上升明显,岸线类型格局变化显著;1995年后,岸线长度增长较缓,但建设用地态势增长强劲。（2）大湾区大陆岸线整体形态上不断曲折化,分形维数逐渐增长;空间位置变化上,大陆岸线不断向海推进,年平均速率达9.91 m/a,向海延伸最远的地方出现在洪奇门至蕉门和虎跳门至鸡啼门岸段附近,最大值可达197.88 m/a。（3）大湾区大陆岸线的开发利用程度及人类活动干预程度处于逐渐增强的趋势,人为影响主要体现为港口码头建筑岸线及围填养殖岸线。（4）大湾区的地形地貌、水文特征等自然环境是岸线演变的基础,社会经济发展和政策是岸线演变的重要驱动因素。在20世纪末,发展速度对海岸线的影响最大;在21世纪初,发展强度则为演变的主要影响因素。  相似文献   

2.
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   

3.
三沙湾海岸线时空演变   总被引：1，自引：0，他引：1  
海岸带是海陆之间的过渡区域,是人类活动和经济发展较为活跃的地区。海岸线时空演变研究对海岸带资源开发与保护有重要意义,但国内外对三沙湾海岸线时空演变研究较少。本文基于25 a的卫星遥感资料,解译出4个时相的三沙湾海岸线,定量分析海岸线变化趋势,并研究海岸线演变的主要因素。研究表明,25 a的三沙湾海岸线总体长度呈增长趋势：1988-1996年岸线总长度变化不大;2003年较1996年增加约6 947 m、增长约11.5%;2003-2013年岸线总长度增加较为明显,2013年较2003年增加约24 128 m、增长约39.6%,其增速约为1996-2003的3.4倍。砂质岸线长度基本稳定,基岩和泥质岸线长度有所减少,人工岸线在逐年增加,这主要是滩地围垦、港口建设和海岸人工改造等人为因素造成的。  相似文献   

4.
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.
C. Pereira  C. Coelho 《Natural Hazards》2013,69(1):1033-1050
Several coastal zones are facing shoreline retreat problems, losing territory due to energetic sea actions, negative sediment transport balances and climate change phenomena. To deal with this problem, efficient tools are necessary to help decision-makers choose the right procedures to follow. These tools should assess, estimate and project scenarios of coastal evolution in a medium-to-long-term perspective. To perform reliable projections, as many variables as possible should be analysed, and the impact of each of these variables on the shoreline evolution should be understood. This study aimed to analyse three climate change phenomena that are considered the most important in a Portuguese west coast stretch (at Aveiro region). The considered phenomena are the wave height increasing due to storms, the wave direction changes and the sea level rise. A shoreline evolution numerical model, long-term configuration, developed to support coastal zone planning and management in relation to erosion problems was applied. This work defined a methodology for classification of risk areas, considering the uncertainty associated with different wave climate sequences on simulations. As a result, different risk maps according to considered climate change effects were obtained, defining areas of high, medium and low risk of territory loss due to erosion. A generalized erosion tendency and shoreline retreat were observed, particularly in the downdrift side of groins. The sea water level rise showed lower impacts in the shoreline evolution than wave direction changes, or wave height increasing, which presents the highest impact.  相似文献   

6.
 Impacts on nearshore sedimentation arising from potential sea level change of the magnitude predicted in Intergovernmental Panel on Climatic Change scenarios associated with global warming are reviewed. For sandy duned coasts, the obvious sedimentation impacts include potential erosion of coastal dunes with implied deposition of the eroded material in the nearshore, possible deepening of embayments, and flooding of wetlands. For the sandy coasts a number of two-dimensional models are available for predicting shoreline change, but there are significant difficulties in applying Bruun-type models for dune erosion and assessment of sediment redistribution over the inner shelf, and for predicting the amount of shoreline retreat for a given rate of sea level rise. If the beach profile contains excessive sand relative to its equilibrium profile, sensu Dean (1991), then shoreline retreat may not occur upon sea level rise. From the evidence of Kiel Bay, at least in these semi-enclosed basin types, it is during major transgressions that maximum deposition in adjacent basins occurs, due to the sea eroding weakly consolidated and weathered surface regolith. But at the same time climatic patterns were re-adjusting and probably contributed to maximum deposition in adjacent shelf and basins below wave base. Received: 16 June 1995 / Accepted: 29 January 1996  相似文献   

7.
Estuarine and beach deposits in the vicinity of the present coastline at Pakarae River record the infilling of an estuary and subsequent development of a sequence of seven marine terraces during Holocene time.

At the maximum of the last glaciation about 18,000 years ago the shoreline at the ancestral Pakarae River was approximately 20 km east of the present shoreline. By about 9000 years BP the sea had transgressed across most of that coastal plain to lie within a few hundred metres of the base of the present coastal hills. Seventeen radiocarbon ages from estuarine deposits record the overall rise in post-glacial sea level, but in the period c. 9500-7000 yrs BP there are reversals to the overall rising trend. Between 9500 and 8500 yrs BP there appears to have been a eustatic fall in sea level of at least 4 m. This observation is supported by data from several other localities around New Zealand. Maximum transgression occurred about 6500–7000 yrs BP when the sea reached the base of hillslopes and an extensive estuary existed behind a barrier bar.

Since that time the barrier bar disappeared, probably due to stranding in an uplift event, and the coastline advanced progressively outward toward its present position. Coastal progradation (sea level regression) and subsequent erosion have occurred in association with episodic large earthquakes at about 6700, 5400, 3910, 2450, 1570, 1000 and 600 yrs BP. The present distribution of terraces has been influenced by coastal erosion, which has removed all trace of some terraces from some areas, and river erosion has modified the marine terraces near the river.  相似文献   


8.
Late Quaternary landscape development along the Rancho Marino coastal range front in the central‐southern Pacific Coast Ranges of California has been documented using field mapping, surveying, sedimentary facies analysis and a luminescence age determination. Late Quaternary sediments along the base of the range front form a single composite marine terrace buried by alluvial fans. Marine terrace sediments overlie two palaeoshore platforms at 5 m and 0 m altitude. Correlation with the nearby Cayucos and San Simeon sites links platform and marine terrace development to the 125 ka and 105 ka sea‐level highstands. Uplift rate estimates based on the 125 ka shoreline angle are 0.01–0.09 m ka?1 (mean 0.04 m ka?1), and suggest an increase in regional uplift along the coast towards the NW where the San Simeon fault zone intersects the coastline. Furthermore, such low rates suggest that pre‐125 ka uplift was responsible for most of the relief generation at Rancho Marino. The coastal range front landscape development is, thus, primarily controlled by post 125 ka climatic and sea‐level changes. Post 125 ka sea‐level lowering expanded the range front piedmont area to a width of 7.5 km by the 18 ka Last Glacial Maximum lowstand. This sea‐level lowering created space for alluvial fan building along the range front. A 45 ± 3 ka optically stimulated luminescence (OSL) age provides a basal age for alluvial fan building or marks the time by which distal alluvial fan sedimentation has reached 300 m from the range front slope. Fan sedimentation is related to climatic change, with increased sediment supply to the range front occurring during (1) glacial period cold stage maxima and/or (2) the Late Pleistocene–Holocene transition, when respective increases in precipitation and/or storminess resulted in hillslope erosion. Sea‐level rise after the 18 ka lowstand resulted in range front erosion, with elevated localised erosion linked to the higher relief and steeper slopes in the SE. This study demonstrates that late Quaternary coastal range front landscape development is driven by interplay of tectonics, climatic and sea‐level change. In areas of low tectonic activity, climatic and sea‐level changes dominate coastal landscape development. When the sea‐level controlled shoreline is in close proximity to the coastal range front, localised patterns of sedimentation and erosion are passively influenced by the pre‐125 ka topography. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

9.
Vizianagaram–Srikakulam coastal shoreline consisting of beaches, mangrove swamps, tidal channel and mudflats is one of the vulnerable coasts in Andhra Pradesh, India. Five site-specific parameters, namely rate of geomorphology, coastal elevation, coastal slope, shoreline change and mean significant wave height, were chosen for constructing coastal vulnerability index and assessing coastal landscape vulnerability. The findings revealed a shift of 2.5 km in shoreline towards the land surface because of constant erosion and that of 1.82 km towards the sea due to accretion during 1997–2017. The rate of high erosion was found in zones IV and V, and high accretion was found in zones II and III. Coastal vulnerability index analysis revealed constant erosion along shoreline and sea level rise in the study area. Most of the coast in zone V has recorded very high vulnerability due to erosion, high slope, significant wave height and sea level rise. Erosion and accretion, significant wave height, sea level rise and slope are attributed to high vulnerability in zones III and IV. Zone II recorded moderate vulnerability. Relatively lower slope, mean sea wave height and sea level rise have made this zone moderately vulnerable. Very low vulnerability was found in zone I, and low vulnerability was recorded in zone II. Accretion, low slope and low sea level rise were found to be causative factors of lower vulnerability. Thus, zones III, IV and V should be accorded higher priorities for coastal management. The findings can be helpful in coastal land planning and management and preparing emergency plans of the coastal ecosystems.  相似文献   

10.
Shoreline changes are largely dependent on coastal morphology. South-west coast of India is a high energy coast characterised by monsoon high waves, steep beach face and medium-sized beach sand. Waves are generally from west and west south-west during rough monsoon season and from south-west during fair weather season. Shoreline change along this coast is studied with reference to coastal morphological features. Various morphological features, modifications and chronological positions of shoreline are analysed with the information derived from multidated satellite imageries, toposheets and GPS shoreline mapping along with extended field survey. Image processing and GIS techniques have been used for the analysis of data and presentation of results. Sediment accumulation on the leeward side of artificial structures such as harbour breakwaters and groynes is used as a sediment transport indicator. Artificial structures such as seawalls, groynes and harbour breakwaters modify morphology. Shoreline south of headlands/promontories and breakwaters are stable or accreting due to net northerly longshore sediment transport while erosion tendency is observed on the north side. Lateritic cliffs fronting the sea or with seasonal beach undergo slumping and cliff edge retreat as episodic events. Spits adjoining tidal inlets are prone to shoreline variations due to oscillations of inlet mouth. Interventions in the form of inlet stabilization and construction of coastal protection structures trigger erosion along adjoining coasts. Seawalls constructed along highly eroding coasts get damaged, whereas those constructed along monsoon berm crest with frontal beaches for protection against monsoon wave attack are retained. Fishing gaps within seawalls are areas of severe temporary erosion during rough monsoon season. Accretion or erosion accompanies construction of harbour breakwaters in a stable coastal plain. Close dependence of shoreline changes on morphology necessitates detailed understanding of impacts on morphology prior to introducing any intervention in the coastal zone.  相似文献   

11.
Densely populated coastal zones of India are highly exposed to natural environment. These are impacted by episodic natural events, continuous coastal process, gradually rising sea levels and coexisting human interventions. The present study is an attempt to assess the implication of the sea level rise and coastal slope in the coastal erosion for entire mainland of India. In this regard, two methods were employed to estimate the shoreline change rate (SCR): (1) satellite-derived SCR using the Landsat TM and ETM+ acquired during 1989–2001 and (2) SCR derived by Bruun Rule using the parameters coastal slope and sea level trend derived from satellite altimetry. Satellite-derived SCR has been compared with the shoreline change estimated based on Bruun Rule, revealing a better agreement with each other in terms of trend. Peaks of shoreline retreat calculated using Bruun model and satellite-observed SCR offset by 25–50 km. Offset in these peaks was observed due to net drift towards north in the east coast and south in the west coast of India, revealing the applicability of the Bruun Rule along the Indian coast. The present study demonstrates that coastal slope is an additional parameter responsible for the movement of shoreline along with sea level change. The results of satellite-derived SCR reveal the highest percentage of erosion along West Bengal coast with 70% followed by Kerala (65%), Gujarat (60%) and Odisha (50%). The coastlines of remaining states recorded less than 50% of coasts under erosion. Results of this study are proving critical inputs for the coastal management.  相似文献   

12.
The famous Cape Hatteras Lighthouse is threatened with destruction by an eroding coastline. Recent attempts to control the erosion have reduced but not stopped it The natural erosion trend for 41 km of coast from Rodanthe to Cape Hatteras was determined, based on 94 years of survey records from 1852 to 1946 At the lighthouse, the natural erosion rate is 7 5 m/yr In 2005, if no further human interference with coastal processes occurs, 190 m of coast will have eroded since 1980, leaving the shoreline nearly 90 m west of the lighthouse Considering the expensive effort being undertaken to protect the lighthouse from destruction, an inventory of property along the Atlantic coast should be made, before other similar projects are initiated We can afford to protect only the most valuable property.  相似文献   

13.
The duration of shoreline occupation at a given sea‐level, coastal response to sea‐level change and the controls on preservation of various shoreline elements can be recognized by detailed examination of submerged shorelines on the continental shelf. Using bathymetric and seismic observations, this article documents the evolution and preservation of an incised valley and lithified barrier complex between ?65 m and ?50 m mean sea‐level on a wave‐dominated continental shelf. The barrier complex is preserved as a series of aeolianite or beachrock ridges backed by laterally extensive back‐barrier sediments. The ridges include prograded cuspate lagoonal shoreline features similar to those found in contemporary lagoons. The incised valley trends shore‐parallel behind the barrier complex and records an early phase of valley filling, followed by a phase of extensive lagoonal sedimentation beyond the margins of the incised bedrock valley. Sea‐level stability at the outer barrier position (ca ?65 m) enabled accumulation of a substantial coastal barrier that remained intact during a phase of subsequent slow sea‐level rise to ?58 m when the lagoon formed. These lagoonal sediments are stripped seawards by bay ravinement processes which caused the formation of several prograded marginal cuspate features. An abrupt rise in sea‐level to ?40 m, correlated with melt‐water pulse 1B, enabled the preservation of thick lagoonal sediments at the top of the incised valley fill and preservation on the sea bed of the cemented core of the barriers. This situation is unique to subtropical coastlines where early diagenesis is possible. The overlying sandy sediment from the uncemented upper portion of the barriers is dispersed by ravinement, partly burying the ridges and protecting the underlying sediments. The high degree of barrier or shoreline preservation is attributed to rapid overstepping of the shoreline, early cementation in favourable climatic conditions and the protection of the barrier cores by sand sheet draping.  相似文献   

14.
This study addresses gaps in understanding the relative roles of sea‐level change, coastal geomorphology and sediment availability in driving beach erosion at the scale of individual beaches. Patterns of historical shoreline change are examined for spatial relationships to geomorphology and for temporal relationships to late‐Holocene and modern sea‐level change. The study area shoreline on the north‐east coast of Oahu, Hawaii, is characterized by a series of kilometre‐long beaches with repeated headland‐embayed morphology fronted by a carbonate fringing reef. The beaches are the seaward edge of a carbonate sand‐rich coastal strand plain, a common morphological setting in tectonically stable tropical island coasts. Multiple lines of geological evidence indicate that the strand plain prograded atop a fringing reef platform during a period of late‐Holocene sea‐level fall. Analysis of historical shoreline changes indicates an overall trend of erosion (shoreline recession) along headland sections of beach and an overall trend of stable to accreting beaches along adjoining embayed sections. Eighty‐eight per cent of headland beaches eroded over the past century at an average rate of ?0·12 ± 0·03 m yr?1. In contrast, 56% of embayed beaches accreted at an average rate of 0·04 ± 0·03 m yr?1. Given over a century of global (and local) sea‐level rise, the data indicate that embayed beaches are showing remarkable resiliency. The pattern of headland beach erosion and stable to accreting embayments suggests a shift from accretion to erosion particular to the headland beaches with the initiation of modern sea‐level rise. These results emphasize the need to account for localized variations in beach erosion related to geomorphology and alongshore sediment transport in attempting to forecast future shoreline change under increasing sea‐level rise.  相似文献   

15.
This paper presents a new method for coastal vulnerability assessment (CVA), which relies upon three indicators: run-up distance (as a measurement of coastal inundation), beach retreat (as a measurement of potential erosion), and beach erosion rate (obtained through the shoreline positions in different periods). The coastal vulnerability analysis of Sele Coastal Plain to storm impacts is examined along a number of beach profiles realized between 2008 and 2009. This particular study area has been selected due to its low-lying topography and high erosion propensity. Results are given in terms of an impact index, performed by combining the response due to coastal inundation, storm erosion, and beach erosion rate. This analysis is implemented on the basis of morphosedimentary characteristics of the beach, wave climate evaluation, and examination of multitemporal aerial photographs and topographic maps. The analysis of the final results evidences different coastal responses as a function of the beach width and slope, which in turn depend on the local anthropization level. The comparison of this method with a Coastal Vulnerability Index method evidences the better attitude of CVA index to take into account the different beach features to explain the experienced damages in specific stretches of the coastline considered.  相似文献   

16.
One of the most effective means of monitoring the cumulative effects of natural processes and human activities on the shoreline is to study the patterns of shoreline change over time. An attempt has been made to study the shoreline changes along Al Batinah, Sultanate of Oman, at the outlet of Wadi Al Hawasnah. The previous studies showed that Al Batinah coastline is generally stable except where coastal engineering structures like harbors, corniches, ports, and recharge dams are present. Remote sensing and GIS techniques are widely used in the coastal geomorphology because they provide the best sources to study the long-term shoreline changes. Rapid shoreline changes at the mouth of Wadi Al Hawasnah have been measured using proxy data derived mainly from satellite images from 2000 to 2005. The mouth of Wadi Al Hawasnah is now completely blocked after the construction of recharge dam at the upper stream of Wadi Al Hawasnah and Wadi Bani Umar in 1995. There has been no discharge to the sea after the construction of the dam. Furthermore, beach profiles of this area show erosion close to the south of the tidal inlet and accretion further south. The shorelines in the northwest of the tidal inlet remained stable.  相似文献   

17.
Clastic, depositional strandplain systems have the potential to record changes in the primary drivers of coastal evolution: climate, sea‐level, and the frequency of major meteorological and oceanographic events. This study seeks to use one such record from a southern Brazilian strandplain to highlight the potentially‐complex nature of coastal sedimentological response to small changes in these drivers. Following a 2 to 4 m highstand at ca 5·8 ka in southern Brazil, falling sea‐level reworked shelf sediment onshore, forcing coastal progradation, smoothing the irregular coastline and forming the 5 km wide Pinheira Strandplain, composed of ca 500 successive beach and dune ridges. Sediment cores, grab samples and >11 km of ground‐penetrating radar profiles reveal that the strandplain sequence is composed of well‐sorted, fine to very‐fine quartz sand. Since the mid‐Holocene highstand, the shoreline prograded at a rate of ca 1 to 2 m yr?1 through the deposition of a 4 to 6 m thick shoreface unit; a 1 to 3 m thick foreshore unit containing ubiquitous ridge and runnel facies; and an uppermost beach and foredune unit. However, the discovery of a linear, 100 m wide barrier ridge with associated washover units, a 3 to 4 m deep lagoon and 250 m wide tidal inlet within the strandplain sequence reveals a period of shoreline transgression at 3·3 to 2·8 ka during the otherwise regressive developmental history of the plain. The protected nature of Pinheira largely buffered it from changes in precipitation patterns, wave energy and fluvial sediment supply during the time of its formation. However, multiple lines of evidence indicate that a change in the rate of relative sea‐level fall, probably due to either steric or ice‐volume effects, may have affected this coastline. Thus, whereas these other potential drivers cannot be fully discounted, this study provides insights into the complexity of decadal‐scale to millennial‐scale coastal response to likely variability in sea‐level change rates.  相似文献   

18.
河北省沙质岸滩存在海岸侵蚀现象,对沙滩旅游、海滩工程建设造成严重威胁,制约河北省海洋经济社会发展。海岸侵蚀监测结果显示,区域海滩滩面受波浪、潮流影响较大,时冲时淤,摆动频繁,沙质岸滩整体处于侵蚀状态,各区段蚀淤情况有所差异,高潮线以上有所淤高,海滩坡度开始变陡,呈下蚀状态。海岸侵蚀灾害已引起沙滩沙质粗化、滩肩变窄、滩坡变陡及基岩裸露比率增多等问题。针对这一突出问题,通过定点测量与遥感监测相结合的方式,研究了河北省海岸线动态演变特征,经计算,河北省各侵蚀岸段海岸侵蚀速率达1.0~4.0m/a,单宽体积侵蚀量-1.42~-19.08m~3/m·a。综合分析显示,人类海岸工程建设、区域海洋水文条件及输砂量减少,是河北省发生海岸侵蚀发生的主要原因。  相似文献   

19.
Analysis of air photographs and maps indicates complex patterns of shoreline changes along the south coast of Vere, Jamaica, between the mouths of the Rio Minho and Milk River. These include up to half a kilometre of shore-normal coastal recession between 1941 and 1991, the largest known shoreline change in Jamaica over the past 60 years. Previously, the coastline had been prograding seawards from a low cliff cut into the Rio Minho alluvial fan, in the process constructing a shore-parallel ridge and lagoon complex. The cliff itself is evidence of earlier coastal erosion. Maps published in 1804 and 1885 confirm the mobility of this coastline in historical times. They suggest that the more easterly complex of shore-parallel lagoons was constructed prior to about 1880, while the more recent, westerly beach ridges developed, at least partly, from progressive destruction of the lagoon complex, following a change in orientation of the Rio Minho mouth in the late 19th Century. Photographs of 1999 indicate the onset of accretion, probably resulting from the gradual onshore movement of massive quantities of sediment deposited off the Rio Minho mouth during the extreme flood event of 1986 and several lesser events in 1988 and the 1990s.  相似文献   

20.
The primary geoindicators appropriate for monitoring environmental changes in the humid tropics are transitory surface water levels, shoreline position, wetlands distribution, coral reefs, landforms, and sediment sequence and composition. Lateral zonations and temporal successions of vegetation also can be used as geoindicators of riverine and shoreline changes. All of these coastal geoindicators are sensitive to regional tectonic processes and anthropogenic alterations and they typically reflect significant changes in coastal conditions such as fluvial processes, coastal energy, water quality, relative sea level, and sediment supply. Where humid tropical coasts coincide with active tectonic margins, indicators of seismic activity are critical to understanding coastal changes associated with co-seismic subsidence or uplift, tsunamis, and liquefaction of coastal sediments. Coastal landforms and sedimentary deposits that record late Quaternary environmental changes include perched fluvial and marine terraces, delta-plain morphologies, crevasse-splay deposits, peats and other paleosols, beach ridges, mud capes, and mud volcanoes. Although these features and deposits typically reflect environmental changes spanning more than 100 years, they are relevant to modern processes, management of coastal lands and resources, and prediction of future conditions. In some regions of the humid tropics, large coastal areas are unaffected by hurricanes or typhoons. Nevertheless, these tropical coasts are vulnerable to other non-storm processes, such as El Niño events, tsunamis, and monsoons that increase water levels, and cause widespread flooding and beach erosion. The environmental and political significance of coastal geoindicators increases when they are integrated and applied to issues of human safety and health such as hazards mapping, risk assessment, and dispersion of contaminated sediments. However, to be relevant, those socio-environmental applications demand accurate predictions of future trends and rates of change.  相似文献   

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