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1.
Sediment accumulation rates were determined at several sites throughout Nauset Marsh (Massachusetts, U.S.A.), a back-barrier lagoonal system, using feldspar marker horizons to evaluate short-term rates (1 to 2 year scales) and radiometric techniques to estimate rates over longer time scales (137Cs,210Pb,14C). The barrier spit fronting theSpartina-dominated study site has a complex geomorphic history of inlet migration and overwash events. This study evaluates sediment accumulation rates in relation to inlet migration, storm events and sea-level rise. The marker horizon technique displayed strong temporal and spatial variability in response to storm events and proximity to the inlet. Sediment accumulation rates of up to 24 mm year−1were recorded in the immediate vicinity of the inlet during a period that included several major coastal storms, while feldspar sites remote from the inlet had substantially lower rates (trace accumulation to 2·2 mm year−1). During storm-free periods, accumulation rates did not exceed 6·7 mm year−1, but remained quite variable among sites. Based on137Cs (3·8 to 4·5 mm year−1) and210Pb (2·6 to 4·2 mm year−1) radiometric techniques, integrating sediment accumulation over decadal time scales, the marsh appeared to be keeping pace with the relative rate of sea-level rise from 1921 to 1993 of 2·4 mm year−1. At one site, the210Pb-based sedimentation rate and rate of relative sea-level rise were nearly similar and peat rhizome analysis revealed thatDistichlis spicatarecently replaced this onceS. patenssite, suggesting that this portion of Nauset Marsh may be getting wetter, thus representing an initial response to wetland submergence. Horizon markers are useful in evaluating the role of short-term events, such as storms or inlet migration, influencing marsh sedimentation processes. However, sampling methods that integrate marsh sedimentation over decadal time scales are preferable when evaluating a systems response to sea-level rise.  相似文献   

2.
《Marine Geology》2006,225(1-4):103-127
This paper examines the spatial and temporal variability in the volumetric sediment balance of Allen Creek marsh, a macro-tidal salt marsh in the Bay of Fundy. The volumetric balance was determined as the balance of inputs of sediments and organic matter via accretion on the marsh surface and outputs of sedimentary material primarily due to erosion of the marsh margin. Changes in marsh surface elevation were measured at 20 buried plates and 3 modified sediment elevation tables from 1996–2002, and detailed margin surveys were conducted in 1997, 1999 and 2001 using a differential global positioning system. Changes in surface area were calculated using GIS overlay analysis and used in conjunction with accretion and erosion data to derive volumetric estimates of gains and losses of sedimentary material in the marsh system.Currently the volumetric sediment balance at Allen Creek marsh is positive. However the processes of erosion and accretion demonstrate seasonal, annual and spatial variability. Inputs to the system include deposition on the marsh surface from sediment laden waters and from ice rafting of sediments. Sediment is deposited onto the marsh surface year round, even during the winter when vegetation cover is sparse, and the amount of deposition in general is not significantly correlated with the frequency of tidal inundations. Based on the data from 1996 to 2002, the mid and high marsh zones experience mean accretion rates of approximately 1.4 cm year− 1 whereas accretion rates in the low marsh region are statistically significantly lower (0.8 cm year− 1). The absolute amount of accretion varies between seasons and from year to year. The main loss to the marsh is through erosion of the marsh margin cliffs which can remove a comparatively large volume of sedimentary material in one mass wasting event and which also decreases the vegetated surface area available for deposition from sediment laden waters. The volume of material removed from the marsh margin almost tripled between 1997 (169 m3) and 2001 (502 m3) following breaching of the side of a tidal creek channel, altering the patterns of margin erosion and deposition in the marsh system. During this time, however, other sheltered areas of the marsh system, such as along the tidal creek banks, showed evidence of new vegetation growth, increasing the amount of vegetated surface area available for deposition.The processes of erosion and deposition on the marsh surface exhibit considerable spatial variability, with different regions of the marsh being more or less sensitive to seasonal variability in the dominant controls influencing sediment deposition and erosion in this system, namely wave activity, vegetation, ice and water depths. A key factor in predicting how a marsh will evolve and respond to a number of different controls, e.g. sea-level rise or reduced sediment supply, is to quantify both accretion of the marsh surface and erosion of the marsh margin, evaluating the marsh system as a volumetric whole. This study demonstrates that a marsh system should be assessed in three dimensions rather than simply as a surface of accumulation. This is particularly important for open coastal marshes exposed to the erosive action of waves.  相似文献   

3.
Salt marshes are potentially threatened by sea level rise if sediment supply is unable to balance the rising sea. A rapid sea level rise is one of the pronounced effects of global warming and global sea level is at present rising at an elevated rate of about 3.4 mm y? 1 on average. This increasing rate of sea level rise should make it possible to study the effect of rapidly rising sea level on salt marsh accumulation. However, such an understanding is generally hampered by lack of available data with sufficient precision. Here we present a high-precision dataset based on detailed radiometric measurements of 137Cs in 10 sediment cores retrieved at a natural and unmanaged micro tidal salt marsh. Two distinct 137Cs-peaks were found in all cores, one peak corresponding to the 1963-maximum caused by testing of nuclear weapons in the atmosphere and the other to the Chernobyl accident in 1986. Salt marsh accretion has generally kept pace with sea level rise since 1963 but comparison of the accumulation rates of minerogenic material in the period 1963–1986 and 1986–2003 revealed a slight decrease in accumulation with time in spite of an observed increase in inundation frequency. The observed decrease in sediment deposition is significant and gives reason for concern as it may be the first sign of a sedimentation deficiency which could be threatening this and other salt marshes in the case of a rapidly rising sea level. Our work demonstrates that the assumption of a constant relationship between salt marsh inundation and sediment deposition is not necessarily valid, even for a salt marsh that receives most of its allocthonous sediment from the adjacent sea. The apparent decrease in sediment deposition indicates that the basic assumption of sufficient sediment supply used in contemporary models dealing with salt marsh accretion is most probably not valid in the present case study and it may well be that this is also the case for many other salt marshes, especially if sea level continues to rise rapidly as indicated by some climate change scenarios.  相似文献   

4.
绿色海堤是传统结构工程与海岸生态系统共同组合而成的新型海堤, 用以应对未来海面上升、风暴加剧给低地海岸防护带来的挑战。需解决的问题主要有海岸生态系统消浪过程及生态系统在海堤体系中的配置方式。理论分析、现场观测、物模数模所获结果表明, 海岸生态系统确有显著的消浪功能: 1) 陆架泥区消浪, 其机制以再悬浮和浮泥运动为主, 底部摩擦为次; 2) 潮滩下部的粉砂细砂滩底部摩擦和推移质运动共同造成波能耗散, 而上部的泥滩则以再悬浮和悬沙输运为主; 3) 在盐沼、红树林、海草床等由植被构成的生态系统, 植物通过形态阻力、茎秆运动来阻滞水流、耗散波能, 其效能高于沉积物床面对波能的耗散; 4) 生物礁主要有珊瑚礁和牡蛎礁, 其消能作用主要通过床面摩擦和波浪破碎, 效能较高, 尤其是在风暴期间。生态系统如何成为海堤的有机组成部分, 尤其是侵蚀型海岸的生态位修复和绿色海堤整体设计, 还需进一步研究相关的科学问题: 与硬质工程结合的盐沼-牡蛎礁的适应性生物学; 未来环境变化条件下生态系统的稳定性; 绿色海堤生态系统空间配置及其与风暴事件的时间尺度匹配; 基于均衡剖面理论的海堤形态优化。  相似文献   

5.
New England salt marshes are dominated by the supratidal high marsh grass, Spartina patens. This grass forms a nearly planar surface, which makes it highly vulnerable to the predicted regime of accelerated sea-level rise (SLR). If the high marsh cannot keep pace with rising sea level it will be transformed to intertidal environments, leading to unusually rapid coastal evolution. Winter processes such as ice-loading of surface peat may degrade the marsh surface. Large volumes of snow and ice compress peat, resulting in shallow compaction and a net loss of elevation in some areas.On the Webhannet marsh in Maine, a simulated ice compaction experiment indicates that thick ice can compress marsh peat (46 cm simulated ‘ice’ produced 6.9 ± 0.3 mm of compaction; 24 cm ‘ice’ produced 3.0 ± 0.8 mm). Experimental data suggest that ice thicknesses greater than 10 cm depress the marsh surface by 2 mm for each cm of total ice thickness. However, surface elevations rebounded to near-control levels within 2 weeks of the removal of simulated ‘ice’ from the surface of the marsh. Normal winter ice accumulations on New England marshes, therefore, do not appear to be sufficient to permanently compact marsh surface peat and lead to loss in marsh surface elevation.  相似文献   

6.
Global climate models have predicted a rise on mean sea level of between 0.18 m and 0.59 m by the end of the 21st Century, with high regional variability. The objectives of this study are to estimate sea level changes in the Bay of Biscay during this century, and to assess the impacts of any change on Basque coastal habitats and infrastructures. Hence, ocean temperature projections for three climate scenarios, provided by several atmosphere–ocean coupled general climate models, have been extracted for the Bay of Biscay; these are used to estimate thermosteric sea level variations. The results show that, from 2001 to 2099, sea level within the Bay of Biscay will increase by between 28.5 and 48.7 cm, as a result of regional thermal expansion and global ice-melting, under scenarios A1B and A2 of the Intergovernmental Panel on Climate Change. A high-resolution digital terrain model, extracted from LiDAR, data was used to evaluate the potential impact of the estimated sea level rise to 9 coastal and estuarine habitats: sandy beaches and muds, vegetated dunes, shingle beaches, sea cliffs and supralittoral rock, wetlands and saltmarshes, terrestrial habitats, artificial land, piers, and water surfaces. The projected sea level rise of 48.7 cm was added to the high tide level of the coast studied, to generate a flood risk map of the coastal and estuarine areas. The results indicate that 110.8 ha of the supralittoral area will be affected by the end of the 21st Century; these are concentrated within the estuaries, with terrestrial and artificial habitats being the most affected. Sandy beaches are expected to undergo mean shoreline retreats of between 25% and 40%, of their width. The risk assessment of the areas and habitats that will be affected, as a consequence of the sea level rise, is potentially useful for local management to adopt adaptation measures to global climate change.  相似文献   

7.
Sediment supply and pre-existing shoreline morphology are crucial factors in controlling coastal changes due to sea-level rise. Using examples from both southeast and northeast Ireland, it can be shown that sea-level change may trigger a sequence of events which leads to both static and dynamic shoreline equilibrium. Cliff erosion and longshore sediment movement in east Co. Wexford has led to injection of sediment onto the shelf, and the growth, under both wave and tide regimes, of linear offshore shoals. These shoals now control the pattern of shoreline erosion and provide a template for possible stepwise evolution of the coast under any future sea-level rise. In contrast, the nearby coast of south Co. Wexford comprises a series of coarse clastic barriers moving monotonously onshore, via overwash processes. Here the behavior of the barrier is conditioned by the antecedent morphology of both the beach face and stream outlet bedforms. Finally, the rock platform coast of Co. Antrim presents a far more resistant shoreline to incident marine processes, yet even here there is strong evidence of present process control over so-called ‘raised’ platforms and embayments. It is concluded that coastal sediment supply and dynamics, together with coastal morphology and its interaction with waves, present a far more complex variety of sea-level indicators than is normally acknowledged.  相似文献   

8.
Louisiana's coastal marshes are experiencing the highest wetland loss rates in the U.S., in part due to subsidence-driven relative sea-level rise. These marshes are also vulnerable to the erosive power of wave attack: 1) on the marsh edge adjacent to open-water bodies, and 2) after the marsh platform is submerged. Marsh shorelines in Barataria Bay, Breton Sound, and the active Balize delta of southeastern Louisiana were examined in areas where the subaerial marsh platform had disappeared since 1932. Vibracore transects of marsh and adjacent bay surface sediments (to 2 m depth) were analyzed using geotechnical, stratigraphic, and radiochemical (137-Cs and 210-Pb) methods, and the subaerial-to-subaqueous transition of the marsh was mapped for elevation using standard stadia rod transit and fathometer measurements. Results indicate that marsh edge erosion of the platform takes place subaqueously until water depths of 1.5 m are reached. This is observed even in interior pond regions, but the shoreface elevation profiles are a function of fetch: exposed open bay sites display greater incision (depth and rate) of the marsh platform than protected interior bay or pond sites. Core stratigraphy reveals that the outer part of the subaqueous platform switches from erosional to depositional as retreat proceeds, covering the incised marsh deposits unconformably with estuarine shelly muds. 137-Cs and excess 210-Pb activity indicates that these muds are deposited within a few decades of subaerial marsh loss. The consistency of the cross-shore profile results suggests that a single profile of equilibrium can approximate the morphology of eroding marsh edges in southeast Louisiana: platform stratigraphy and resistance to erosion have a limited effect on profile shape. This equilibrium profile and remote sensing images of shoreline change are used to estimate the sediment yield to adjacent estuarine areas by this process. On average, 1.5 m3 of sediment are yielded per m shoreline length annually from both Barataria Bay and Breton Sound. Due to the highly organic nature of the eroded sediment (30%), this supply of organic-rich material could significantly impact estuarine productivity and hypoxia on the Louisiana continental shelf.  相似文献   

9.
A large deficit in the coastal sediment budget, high rates of relative sea-level rise (~0.9 cm/year), and storm-induced current and wave erosion are forcing barrier shoreface retreat along the periphery of the Mississippi River delta plain. Additionally, conversion of interior wetlands to open water has increased the bay tidal prism, resulting in degradation of barrier islands due to inlet widening, formation of new inlets, and sediment sequestration at ebb-tidal deltas. Single-beam bathymetric surveys along a 165-km stretch of south-central Louisiana barrier coast, from Raccoon Point in Terrebonne Parish to Sandy Point in Plaquemines Parish, were conducted in 2006. These data, combined with historical bathymetry from three time periods (dating to the 1880s), provide a series of digital elevation models that were used to calculate sediment volumetric changes and determine long-term erosional-depositional trends. Dominant patterns during the 125-year period include (1) erosion of ~1.6 × 109 m3 from the shoreface, forcing up to 3 km of shoreface retreat, (2) sediment deposition in coastal bights and at ebb-tidal deltas, and (3) a combined increase in tidal inlet cross-sectional area from ~41,400 m2 to ~139,500 m2. Bathymetric and shoreline change datasets separated by shorter time periods (sub-annual) demonstrate that these long-term trends are driven by processes associated with major hurricane impacts, and that rates of shoreface erosion are an order of magnitude greater during active hurricane seasons compared to long-term trends.  相似文献   

10.
De-embankment in the salt marshes of the island of Langeoog was carried out in 2004, thereby inducing an artificial transgression within an area of 2.2 km2. Material from three suspended matter traps (SMTs) located along a N–S transect was collected monthly between January 2006 and February 2007. Besides geochemical (major and trace elements) and grain-size analyses, the duration and height of water cover were continuously measured by pressure gauges during the sampling period at two sites, thus revealing inundation frequency (max. 280 year−1) and level (max. 2.4 m). Generally, the silt-dominated SMT material exhibits a geochemical composition similar to that of suspended particulate matter from the adjacent Wadden Sea. However, distinctly increasing enrichments of TOC, P, Mn and Mo from the shoreline towards the higher salt marsh clearly indicate fractionation processes during material transport. Geochemical comparison with older Holocene coastal deposits reveals a mixture of brackish and tidal flat sediments, thus reflecting an early stage of sea-level rise and the development from a terrestrial towards a marine-dominated system. Sedimentation rates are higher than the local sea-level rise, as revealed by vertical salt marsh growth. Storm surges deliver the highest amounts of sediment and play an important role in salt marsh accumulation within the study area. Average accumulation rates of TOC (780 t year−1), P (54 t year−1) and Mn (5.2 t year−1) in the de-embanked area suggest that the former sand-dominated sediments currently receive significant amounts of reactive organic-rich material, thus fostering biogeochemical cycling.  相似文献   

11.
Marsh vertical accretion via vegetative growth   总被引：1，自引：0，他引：1  
Coastal marshes accrete vertically in response to sea-level rise and subsidence. Inadequate accretion and subsequent conversion of coastal marshes to open water generally is attributed to inadequate mineral sedimentation because mineral sedimentation is widely assumed to control accretion. Using 137Cs dating to determine vertical accretion, mineral sedimentation, and organic matter accumulation, we found that accretion varied with organic accumulation rather than mineral sedimentation across a wide range of conditions in coastal Louisiana, including stable marshes where soil was 80% mineral matter. These results agreed with previous research, but no mechanism had been proposed to explain accretion via vegetative growth. In an exploratory greenhouse experiment, we found that flooding stimulated root growth above the marsh surface. These results indicated the need for additional work to determine if flooding controls accretion in some marshes by stimulating root growth on the marsh surface, rather than by mineral accumulation on the marsh surface. Restoration or management that focus on mineral sedimentation may be ineffective where a relationship between accretion and mineral sedimentation is assumed rather than tested.  相似文献   

12.
海岸线变化对海岸带生态环境改变、滨海土地侵蚀有着极其重要的影响,海岸线的提取和监测对海岸带生态系统的保护和管理具有重要意义。本研究基于数字化海岸线分析系统(DSAS,Digital Shoreline Analysis System),研究了黄河三角洲和莱州湾的海岸线时空变化规律。研究结果表明:通过提取1985-2015年6期的Landsat影像,发现近30年来黄河三角洲和莱州湾地区海岸线均呈现显著的向海方向扩张的趋势,且增长速率逐渐加快。黄河三角洲的终点变化速率(EPR,End Point Rate)约为73.0 m/a、线性回归速率(LRR,Linear Regression Rate)约为75.5 m/a,黄河港-大咀沟增长速度最快(129.2 m/a),受黄河泥沙输送的影响,黄河口和老黄河口岸线的几何形态呈现平滑的变化趋势;莱州湾岸线的EPR和LRR约为139.5 m/a和144.3 m/a,淄脉河河口-白浪河河口段增长速度最快(197.6 m/a),岸线变化较为显著的区域主要集中在港口、圈海堤坝、海水养殖等的地方。DSAS模型在海岸线定量化分析中具有显著优势,利用EPR和LRR指标能够科学有效地模拟岸线在时间和空间上的变化速率。  相似文献   

13.
Since the 1980s, the coastal wetlands in Korea have been rapidly degraded and destroyed mainly due to reclamation and landfills for coastal development. In order to recover damaged coastal environments and to develop wetland restoration technologies, a 4-year study on ecological the restoration of coastal vegetated ecosystems was started in 1998. As one of a series of studies, a small-scale experiment on salt marsh restoration was carried out from April 2000 to August 2001. The experiment was designed to find effective means of ecological restoration through a comparison of the changes in environmental components and species structure between two different experimental plots created using sediment fences, one with and one without small canals. Temporal variation in surface elevation, sedimentary facies, and benthic species were measured seasonally in each plot and in the adjacent natural reference sites. Monthly exposure occurred from 330 cm to mean sea level, which represents the critical tidal level (CTL) at which salt marsh plants colonize. Vegetation, especially Suaeda japonica, colonized the site the following spring and recovered to a similar extent in the natural marshes 16 months later. The sedimentary results indicated that the sediment fences had effects on particle size and sediment accumulation, especially in the plot with small canals. This experiment also showed that tidal height, especially that exceeding the CTL, is an important factor in the recovery of the benthic fauna of salt marshes. From these results, we suggested that designs for the restoration of salt marsh ecosystems must consider the inclusion of a tidal height exceeding CTL, as this may allow reconstruction of the previous natural ecosystem without artificial transplanting.  相似文献   

14.
Udupi coast in Karnataka state, along the west coast of India, selected as a study area, is well known for sandy beaches, aquaculture ponds, lush greenery, temples and major and minor industries. It lies between 13°00′00″–13°45′00″ north latitudes and 74°47′30″–74°30′00″ east longitudes, the length of the coastline is 95 km, and is oriented along the NNW–SSE direction. It is vulnerable to accelerated sea level rise (SLR) due to its low topography and its high ecological and touristy value. The present study has been carried out with a view to calculate the coastal vulnerability index (CVI) to know the high and low vulnerable areas and area of inundation due to future SLR, and land loss due to coastal erosion. Both conventional and remotely sensed data were used and analysed through the modelling technique and by using ERDAS Imagine and geographical information system software. The rate of erosion was 0.6018 km2/yr during 2000–2006 and around 46 km of the total 95 km stretch is under critical erosion. Out of the 95 km stretch coastline, 59% is at very high risk, 7% high, 4% moderate and 30% in the low vulnerable category, due to SLR. Results of the inundation analysis indicate that 42.19 km2 and 372.08 km2 of the land area will be submerged by flooding at 1 m and 10 m inundation levels. The most severely affected sectors are expected to be the residential and recreational areas, agricultural land, and the natural ecosystem. As this coast is planned for future coastal developmental activities, measures such as building regulation, urban growth planning, development of an integrated coastal zone management, strict enforcement of the Coastal Regulation Zone (CRZ) Act 1991, monitoring of impacts and further research in this regard are recommended for the study area.  相似文献   

15.
Climate change poses a significant challenge for the future of Northern Ireland’s coast due to impacts that include, inter alia, mean sea level rise of between 13 cm and 74 cm by 2050. Whilst flooding is regarded as a major hazard in the United Kingdom (UK), to date Northern Ireland’s experiences of coastal flooding have been infrequent and less severe compared to those in England and Wales. Similarly, coastal erosion has historically been, and remains, only a minor concern in Northern Ireland. Partly as a result of this, Government administrative arrangements for Flood and Coastal Erosion Risk Management (FCERM) in Northern Ireland operate in the absence of any statutory provision for coastal erosion, as well as without formal or strategic shoreline management planning and any integrated flood and coastal erosion risk management policy. This paper provides a commentary on Northern Ireland’s approach to FCERM, comparing this with its UK counterparts, highlighting both congruence and divergence in policy evolution and development. It is noted that the recent EU Floods Directive has been a significant catalyst and that the current institutional landscape for FCERM is in flux.  相似文献   

16.
Salt marshes accrete both organic and inorganic sediments. Here we present analytical and numerical models of salt marsh sedimentation that, in addition to capturing inorganic processes, explicitly account for above- and belowground organic processes including root growth and decay of organic carbon. The analytical model is used to examine the bias introduced by organic processes into proxy records of sedimentation, namely 137Cs and 210Pb. We find that accretion rates estimated using 210Pb will be less than accretion rates estimated using the 137Cs peak in steadily accreting marshes if (1) carbon decay is significant and (2) data for 210Pb extend below the 137Cs peak. The numerical model expands upon the analytical model by including belowground processes such as compaction and root growth, and by explicitly tracking the evolution of aboveground biomass and its effect on sedimentation rates. Using the numerical model we explore how marsh stratigraphy responds to sediment supply and the rate of sea-level rise. It is calibrated and tested using an extensive data set of both marsh stratigraphy and measurements of vegetation dynamics in a Spartina alterniflora marsh in South Carolina, USA. We find that carbon accumulation in marshes is nonlinearly related to both the supply of inorganic sediment and the rate of sea-level rise; carbon accumulation increases with sea-level rise until sea-level rise reaches a critical rate that drowns the marsh vegetation and halts carbon accumulation. The model predicts that changes in carbon storage resulting from changing sediment supply or sea-level rise are strongly dependent on the background sediment supply: if inorganic sediment supply is reduced in an already sediment poor marsh the storage of organic carbon will increase to a far greater extent than in a sediment-rich marsh, provided that the rate of sea-level rise does not exceed a threshold. These results imply that altering sediment supply to estuaries (e.g., by damming upstream rivers or altering littoral sediment transport) could lead to significant changes in the carbon budgets of coastal salt marshes.  相似文献   

17.
This study investigated the spatial and temporal variations of sediment accumulation and their impacts on coral communities in four sites at two or three depths (3 m, 6 m and 9 m) at the Sanya Coral Reef Reserve by deploying sediment traps on the sea floor during 2007–2009. Rainfall and typhoon events, which appeared to control sediment accumulation in the sea floor of the coral reef, were positively correlated with total sediment and sand-sized (i.e. 63–2000 µm) sediment accumulation. Sediment accumulation rate significantly decreased with the distance far away from the coast in Sanya. The mean sediment accumulation rates in Ximaozhou, Luhuitou and Xiaodonghai during 2007 to 2009 were close to 20 mg cm−2 d−1, and they were significantly higher than that in Yalongwan, probably as a result of terrestrial soil erosion caused by strong coast human activities (e.g. coastal construction, dredging and hillside clearing). Correlation analysis revealed that silt-clay-sized sediment accumulation rate was highly negatively correlated with total live coral cover and coral cover in some taxa, such as Montipora and branching Porites. whereas, Diploastrea heliopora was positively correlated with silt-clay-sized sediment accumulation. Correlation analysis also suggested that silt-clay-sized sediment accumulation had a higher efficiency in predicting the spatial variation of total live coral cover in Sanya than did the total sediment accumulation. Based on this investigation, we conclude that high rates of sediment accumulation pose a severe threat to the Sanya Coral Reef Reserve, highlighting the importance of integrated watershed management practices in the Sanya Coral Reef Reserve.  相似文献   

18.
布容法则及其在中国海岸上的应用   总被引：12，自引：1，他引：11  
布容（Ｂｒｕｕｎ）法则是预测海平面上升引起海岸侵蚀最早的方法也是最简单的方法。根据中国砂质和淤泥质海岸的情况,布容法则可定性地解释海平面上升与海岸侵蚀的关系,在满足它要求条件的海岸地段和发育时期,用它预测海岸侵蚀或许是可能的。但是,若不严格审查海岸环境和条件,把它作为海平面上升情况预测海岸侵蚀的普遍模式,有待更多的研究加以证明。  相似文献   

19.
《Ocean & Coastal Management》2006,49(7-8):462-475
A mangrove ecosystem shows close links between geomorphology and vegetation assemblage. In addition, the vegetation can change over time as landforms can accrete or erode, which is a direct response to coastal sedimentary processes. This demonstrates that significant changes can occur on short time scales and mangroves provide an excellent register of these modifications. Therefore, mangrove morphology and sedimentation are good indicators of interactions between relative sea level changes, coastal processes and sediment supply. These interactions are responsible for landward migration of the shoreline (erosion) and seaward migration of the shoreline (accretion), which is possible to detect from multi-date satellite data and field observations. Mangroves are one of the best geo-indicators in global coastal change research and they are an excellent procedure to detect and quantify coastal modifications.  相似文献   

20.
Sediment collections on a mainland fringing marsh, a lagoon marsh and a barrier island fringing marsh were conducted in conjunction with Geographic Information Systems (GIS) analysis of aerial photographs to relate changes in marsh area to sedimentary processes. The island marsh lost 7·2% of its area in 8 years by overwash. The lagoon marsh lost 10·6% of its area over 41 years by recession of marsh edges. The mainland marsh area increased by 8·2% over 50 years, primarily by upland encroachment. Surface sediment was collected monthly at the mainland and lagoon marshes for 1 year to identify changes in the mean grain size, organic content and mass of sediment deposited on sampling plates. Short-term variability in these characteristics obscured seasonal differences. Grain size and monthly sediment accumulation decreased towards the interior of both marshes, while the organic matter content increased. On the lagoon marsh, coarse sediment at creekside stations, as well as grain size contrasts between surface and subsurface sediment, are consistent with erosion evident in GIS analysis. On the mainland marsh, sediment does not vary as much with location or depth, and topography appears stable. Tidal currents appear to be competent to resuspend most particle sizes represented in surface sediment samples, including aggregates, except at the edge of the lagoon site. Decreasing rates of marsh edge change reflect moderation of oceanic processes, while the interior of both lagoon and mainland marshes remained stable throughout the study. Both lagoon marsh losses to recession and mainland marsh gains from upland reflect the submergence which this shoreline experiences.  相似文献   

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