Simulation of Storm Surges Along Myanmar Coast Using a Location Specific Numerical Model

Coastal flooding induced by storm surges associated with tropical cyclones is one of the greatest natural hazards sometimes even surpassing earthquakes. Although the frequency of tropical cyclones in the Indian seas is not high, the coastal region of India, Bangladesh and Myanmar suffer most in terms of life and property caused by the surges. Therefore, a location-specific storm surge prediction model for the coastal regions of Myanmar has been developed to carry out simulations of the 1975 Pathein, 1982 Gwa, 1992 Sandoway and 1994 Sittwe cyclones. The analysis area of the model covers from 8° N to 23° N and 90° E to 100° E. A uniform grid distance of about 9 km is taken along latitudinal and longitudinal directions. The coastal boundaries in the model are represented by orthogonal straight line segments. Using this model, numerical experiments are performed to simulate the storm surge heights associated with past severe cyclonic storms which struck the coastal regions of Myanmar. The model results are in agreement with the limited available surge estimates and observations.     

渤海湾东南海岸风暴潮成因分析及预报

根据渤海湾东南海岸历史及实测潮水、气象、地理资料,分析产生风暴潮的原因,研究风暴潮规律；分析了东北大风与风暴潮增水、天文潮与风暴潮出现时间的关系；建立了埕口站风暴潮预报方案,成功预报了渤海湾东南海岸埕口站附近海域1997、2003年风暴潮,为渤海湾东南海岸防灾、减灾提供科学依据。     

Importance of Biogeomorphic and Spatial Properties in Assessing a Tidal Salt Marsh Vulnerability to Sea-level Rise

We evaluated the biogeomorphic processes of a large (309 ha) tidal salt marsh and examined factors that influence its ability to keep pace with relative sea-level rise (SLR). Detailed elevation data from 1995 and 2008 were compared with digital elevation models (DEMs) to assess marsh surface elevation change during this time. Overall, 37 % (113 ha) of the marsh increased in elevation at a rate that exceeded SLR, whereas 63 % (196 ha) of the area did not keep pace with SLR. Of the total area, 55 % (169 ha) subsided during the study period, but subsidence varied spatially across the marsh surface. To determine which biogeomorphic and spatial factors contributed to measured elevation change, we collected soil cores and determined percent and origin of organic matter (OM), particle size, bulk density (BD), and distance to nearest bay edge, levee, and channel. We then used Akaike Information Criterion (AICc) model selection to assess those variables most important to determine measured elevation change. Soil stable isotope compositions were evaluated to assess the source of the OM. The samples had limited percent OM by weight (<5.5 %), with mean bulk densities of 0.58 g cm^-3, indicating that the soils had high mineral content with a relatively low proportion of pore space. The most parsimonious model with the highest AICc weight (0.53) included distance from bay's edge (i.e., lower intertidal) and distance from levee (i.e., upper intertidal). Close proximity to sediment source was the greatest factor in determining whether an area increased in elevation, whereas areas near landward levees experienced subsidence. Our study indicated that the ability of a marsh to keep pace with SLR varied across the surface, and assessing changes in elevation over time provides an alternative method to long-term accretion monitoring. SLR models that do not consider spatial variability of biogeomorphic and accretion processes may not correctly forecast marsh drowning rates, which may be especially true in modified and urbanized estuaries. In light of SLR, improving our understanding of elevation change in these dynamic marsh systems will play a crucial role in forecasting potential impacts to their sustainability and the survival of these ecosystems.     

南海北部长湾风暴潮贝壳堤的沉积特征及发育模式

南海北部长湾贝壳堤是一典型的风暴潮成因贝壳堤。该贝壳堤的横向、纵向露头和钻孔所显示的地层结构、层理特征、粒度特征、14C测年、物质组成、贝屑种属生境及当地风暴增水高度和地壳升降幅度表明:①贝壳堤由风暴沉积组成,是风暴潮增水期间海岸沉积物堆积的结果,由于堆积在平均高潮面之上,增水退却后不受正常天气下波浪的影响得以保存;②理想剖面由下而上分4个部分:潮滩堆积、激浪带堆积、增水面下波浪堆积和增水面上波浪爬高堆积,各个部分具有不同的沉积特征,分别代表贝壳堤向上增长的各个阶段的沉积环境和风暴作用方式;③风暴潮贝壳堤与非风暴潮贝壳堤不仅在发育过程,而且在沉积结构、粒度特征、贝屑种属、堆积部位、堆积高度及环境意义等方面都有所不同。     

Research Progress of Coastal Dunes Response to Storm

The major areas of world coastal dunes have been frequently attacked by storms. The storm, as a high energy influential factor for the formation and evolution of coastal dunes, is also one of the important research contents on the surf zone-beach-dune interaction. The research progress are reviewed from the following aspects: Coastal dune morphological response to storms, coastal dune sediments response to storms, mechanisms of coastal dunes in response to storms, and the research methods and techniques used in the research on coastal dunes to storms. Finally, open questions and future developments were suggested.     

Impact of a Tropical Cyclone on Coastal Upwelling Processes

A three-dimensional numerical model is described to study theresponse of a coastal ocean excited by a tropical cyclone in the Bay of Bengal. The numericalexperiments have been carried out using the model to understand the dynamics and thermodynamics ofthe ocean due to different cyclonic systems approaching in different directions. In the firstexperiment, the model is used to simulate the vertical thermal structure of the ocean as a response ofpassage of the less intensified 1997 cyclone, which was skirting the east coast of India before crossingthe Bangladesh coast. The simulations are compared with the buoy data available during the storm period.In the next experiment, it is considered an idealized cyclone with hurricane winds movingnormal to the east coast of India crossing between Visakhapatnam and Kakinada to evolve thermalstructure and currents of the ocean. A net decrease of the SST of 6–7 °C is simulated whenthe severe cyclonic storm moved over the coastal ocean.     

压实作用下广西典型红树林区沉积速率及海平面上升对红树林迁移效应的制衡

气候变化造成的海平面上升是迫使红树林向陆迁移的主要驱动力, 而其自身通过捕沙促淤不同程度的减缓了海平面上升速率的影响。基于广西典型红树林区8根短柱的210Pb测年和含水率分析, 以考虑/未考虑沉积物压实作用为研究情景, 通过对比研究红树林区潮滩地表高程抬升速率和相对海平面上升速率的大小关系, 揭示当前海平面上升对广西红树林向陆/向海迁移的驱动机制。研究发现:未考虑压实作用下的沉积速率约是考虑压实作用下沉积速率的1.00~1.34倍(平均1.12倍), 压实作用明显;压实沉积速率介于0.16~0.78 cm/a, 其底层压实沉积速率与潮滩地表高程抬升速率相等。压实作用下, 英罗湾和丹兜海红树林区的地表高程抬升速率小于相对海平面上升速率;与未考虑压实作用得到的结论相悖。由于广西红树林海岸大都建有防波堤, 限制了红树林向陆的迁移;表明英罗湾和丹兜海的红树林正面临海平面上升的威胁。压实作用校正与否对地表高程抬升速率与相对海平面上升速率相当的区域尤为重要。     

Three-Dimensional Modeling of Storm Surge and Inundation Including the Effects of Coastal Vegetation

Two-dimensional (2D) and three-dimensional (3D) hydrodynamic models are used to simulate the hurricane-induced storm surge and coastal inundation in regions with vegetation. Typically, 2D storm surge models use an enhanced Manning coefficient while 3D storm surge models use a roughness height to represent the effects of coastal vegetation on flow. This paper presents a 3D storm surge model which accurately resolves the effects of vegetation on the flow and turbulence. First, a vegetation-resolving 1DV Turbulent Kinetic Energy model (TKEM) is introduced and validated with laboratory data. This model is both robust enough to accurately model flows in complex canopies, while compact and efficient enough for incorporation into a 3D storm surge-wave modeling system: Curvilinear Hydrodynamics in 3D-Surface WAves Nearshore (CH3D-SWAN). Using the 3D vegetation-resolving model, three numerical experiments are conducted. In the first experiment, comparisons are made between the 2D Manning coefficient approach and the 3D vegetation-resolving approach for simple wind-driven flow. In a second experiment, 2D and 3D representations of vegetation produce similar inundations from the same hurricane forcing, but differences in momentum are found. In a final experiment, varying inundation between seemingly analogous 2D and 3D representations of vegetation are demonstrated, pointing to a significant scientific need for data within wetlands during storm surge events. This study shows that the complex flow structures within vegetation canopies can be accurately simulated using a vegetation-resolving 3D storm surge model, which can be used to assess the feasibility for future wetland restoration projects.     

A Historical Record of Coastal Floods in Britain: Frequencies and Associated Storm Tracks

This paper examines flood frequencies in three coastal sectors of Britain and analyses the associated storm tracks and their principal pathways. The results indicate that the east coast of Britain has suffered most floods over the last 200 years. The frequencies of flood incidents in the south and southwest coast of Britain have increased, particularly during the 20th century, whereas on the west coast flood frequencies have declined. Three distinctive pathways of storm track are identified, related to flood incidents in each coastal sector. A southern pathway in a corridor along the 55° N parallel is associated with flood incidents recorded on the south and southwest coast, whilst storms that are associated with floods on the west coast concentrate along the 60° N parallel. The relationship between the frequencies of floods and climatic variations needs to be explored further. However, the development of coastal settlements has certainly increased vulnerability, and hence the risk of flood disasters.     

Quantification of the Attenuation of Storm Surge Components by a Coastal Wetland of the US Mid Atlantic

Coastal wetlands are receiving increased consideration as natural defenses for coastal communities from storm surge. However, there are gaps in storm surge measurements collected in marsh areas during extreme events as well as understanding of storm surge processes. The present study evaluates the importance and variation of different processes (i.e., wave, current, and water level dynamics with respect of the marsh topography and vegetation characteristics) involved in a storm surge over a marsh, assesses how these processes contribute to storm surge attenuation, and quantifies the storm surge attenuation in field conditions. During the Fall of 2015, morphology and vegetation surveys were conducted along a marsh transect in a coastal marsh located at the mouth of the Chesapeake Bay, mainly composed of Spartina alterniflora and Spartina patens. Hydrodynamic surveys were conducted during two storm events. Collected data included wave characteristics, current velocity and direction, and water levels. Data analysis focused on the understanding of the cross-shore evolution of waves, currents and water level, and their influence on the overall storm surge attenuation. Results indicate that the marsh area, despite its short length, attenuates waves and reduces current velocity and water level. Tides have a dominant influence on current direction and velocity, but the presence of vegetation and the marsh morphology contribute to a strong reduction of current velocity over the marsh platform relative to the currents at the marsh front. Wave attenuation varies across the tide cycle which implies a link between wave attenuation and water level and, consequently, storm surge height. Storm surge reduction, here assessed through high water level (HWL) attenuation, is linked to wave attenuation across the front edge of the marsh; this positive trend highlights the reduction of water level height induced by wave setup reduction during wave propagation across the marsh front edge. Water level attenuation rates observed here have a greater range than the rates observed or modeled by other authors, and our results suggest that this is linked to the strong influence of waves in storm surge attenuation over coastal areas.     

海南岛东南部海岸砂丘风暴冲越沉积记录

通过海南岛东南部海岸详细的古风暴学考察,在尖岭海岸发现了含有风暴冲越沉积物的海岸沙丘剖面,分别命名为JL-1和JL-2剖面,试图从海岸沙丘沉积记录中提取历史上的风暴事件信息。沉积物粒度、磁化率等参数的指标分析表明,这两个剖面含有典型的风暴冲越沉积物,利用放射性核素AMS14C测年、OSL测年分析,并结合历史文献记载,确定这些风暴沉积层是多次台风作用的产物,其形成机制与风暴浪越过海岸沙丘的堆积有关,风暴流越过沙丘顶部后不能回流,导致风暴流携带的沉积物迅速沉积。此外,依据Stockdon经验公式计算结果,该地点沉积记录所代表的最大风暴事件相当于100到200年一遇的重现期。研究表明,该处海岸沙丘冲越沉积含有南海台风强度与重现期的重要信息。     

Epeiric Sea Formation on Neoproterozoic Supercontinent Break-up: A Distinctive Signature in Coastal Storm Bed Amalgamation

Literature review underlines uncertainty in the configuration of the Neoproterozoic supercontinent, (with Rodinia and Palaeopangaea reconstructions enjoying wide support), that stems primarily from inadequate palaeomagnetic data. Nonetheless, breakup of this supercontinent at ca. 0.65 Ga was conducive for epeiric sea formation globally. In the Vindhyan basin, India, a carbonate depositing sea developed over a fluvial-aeolian plain, at approximately 0.6 Ga. The top part of the Vindhyan Supergroup, the Upper Bhander Sandstone, was, however, able to prograde because of a decline in the rate of relative sea level rise. Within this general setting, temporal increases in this rate caused storm deposition at the coastline, largely in a supralittoral setting. Bizarre amalgamation of these storm beds without erosion likely owes its origin to severe curtailment of the velocity of the downwelling flow on the very gentle, muddy coastal slopes, and is thought to be a hallmark of deposition in an open epeiric setting. The storm domination in the Bhander embayment shelf is compatible with the Palaeopangaea supercontinental configuration.     

Effects of an Acute Hypoxic Event on Microplankton Community Structure in a Coastal Harbor of Southern California

Fish mortality and hypoxic events occur in many coastal and inland systems and may result from natural or anthropogenically mediated processes. The effects of consequent changes in water biogeochemistry have been investigated for communities of benthic invertebrates and pelagic metazoans. The responses of micro-plankton assemblages, however, have remained largely unstudied. The northern basin of King Harbor, a small embayment within Santa Monica Bay, CA, USA, suffered a massive fish kill in March 2011 as a consequence of acute hypoxia. Dissolved oxygen concentrations < 0.1 ml?l^?1 were measured in the northern basin of the harbor for several days following the mortality event, and a strong spatial gradient of oxygen was observed from the northern basin to waters outside the harbor. The microplankton community within King Harbor differed significantly from a diatom-dominated community present in neighboring Santa Monica Bay. The latter region appeared unaffected by physicochemical changes, induced by the fish kill, that were observed within the harbor. A trophic shift was observed throughout King Harbor from a photoautotrophic-dominated assemblage to one of heterotrophic forms, with relative abundances of bacterivorous ciliates increasing by more than 80 % in the most impacted part of the harbor. Significant changes in community structure were observed together with dramatically reduced photosynthetic yield of the remaining phytoplankton, indicating severe physiological stress during the extreme hypoxia.     

台风风暴潮影响下潮滩沉积动力模拟初探--以江苏如东海岸为例

以江苏如东潮滩为研究区,采用沉积动力学垂向二维概念模型来模拟正常天气和台风期间潮滩沉积的空间分布特征,探讨台风风暴潮对潮滩正常沉积层序的改造作用.模拟结果表明,在涨落潮时间-流速对称特征明显的如东海岸,潮汐作用使潮滩沉积呈显著的分带性,且剖面形态向“双凸形”演化,两个“凸点”分别位于平均高潮位和平均低潮位附近.在台风期间风暴增水效应下,开边界悬沙浓度差异将导致潮滩冲淤和沉积分布格局的变化,潮上带和潮间带上部均堆积泥质沉积物,潮间带中下部在风暴过程中普遍遭受不同程度的砂质沉积物侵蚀或之后堆积泥质沉积物,在沉积层序中形成风暴冲刷面.因此,潮滩的风暴沉积记录存在于潮间带上部或更高部位.以此模型为基础,可进一步综合考虑极浅水边界层水动力结构、沉积物粒度分布变化、波-流联合作用、台风降水、互花米草等生物活动、潮沟摆动及人工围垦等因素,从而建立风暴事件在沉积层序中的时间序列,更好地解译沉积记录中的古环境信息.     

Assessment of Plant Community Characteristics in Natural and Human-Altered Coastal Marsh Ecosystems

Salt marsh ecosystems provide many critical ecological functions, yet they are subject to considerable disturbance ranging from direct human alteration to increased inundation due to climate change. We assessed emergent salt marsh plant characteristics in the Tuckerton Peninsula, a large expanse (~ 2000 ha) of highly inundated habitat along the southern New Jersey coast, USA. Key salt marsh plant parameters were monitored in the heavily grid-ditched northern segment, Open Marsh Water Management (OMWM) altered central segment, and the shoreline altered southern segment of the peninsula in the summer months of 2011 and 2013. Plant species composition and three metrics of abundance and structure (maximum canopy height, percent areal cover, and shoot density) were examined among marsh segments, along transects within segments, seasonally by month and between years. Despite seasonal or annual variability, the northern segment of the marsh differed in plant species composition from the central and southern segments. This difference was partly due to greater percent areal cover in the northern segment of upper marsh species such as Spartina patens and Distichlis spicata. S. patens also exhibited higher shoot densities in the northern segment than the central segment. Despite the higher abundance of upper marsh species, marsh surface elevations were lower in the northern segment than in the central or southern segments, suggesting the influence of altered hydrology due to human activities. Understanding current variation in the emergent salt marsh vegetation along the peninsula will help inform future habitat change in other coastal wetlands of New Jersey and the mid-Atlantic region subject to natural and anthropogenic drivers.     

中国北方沙尘灾害影响因子分析

利用中国北方1951—2000年188个沙尘暴代表站的气象观测数据和1983—2000年EROS数据中心NDVI数据,对我国北方沙尘灾害的影响因子进行了分析。主要结论有：①在影响沙尘暴发生、发展、演化的自然因子中,植被覆盖度、降水、大风日数和温度起关键作用,夏季植被覆盖度对来年春季沙尘暴发生频次影响较大,降水和温度主要表现在对地表植被覆盖等与沙尘暴有关的地表参数的影响;②大风日数和温度是沙尘暴形成的动力因子,植被覆盖度和降水是阻力因子。沙尘暴日数和持续时间的变化,主要取决于动力因子与阻力因子的综合作用;③遏制沙尘灾害的治本办法,不在于治理沙尘暴本身,而在于消除产生土地退化、生态安全下降的社会原因,处理好发展与生态环境建设的关系。     

中国海台风风暴潮预报模式的研究与应用

本文建立了一个二维的台风风暴潮动力数值模式.采用有限差分技术求解流体运动方程,方程中考虑了有限振幅的影响和科氏参数随纬度的变化,略掉了对流项.无因次分析方法被用于选取最有代表性的台风域中的气压场分布公式.该模式输出产品能够很好地反映一次风暴潮在时间和空间上的变化,便于使用.     

City-Based Risk Assessment of Sea Level Rise Using Topographic and Census Data for the Turkish Coastal Zone

Turkish coastal zone elevation to sea level rise was illustrated using a digital elevation model and methods in a geographical information system. It was intended to determine several parameters such as population, settlements, land use, wetlands, contribution to national agricultural production, and taxes at risk using high-resolution Shuttle Radar Topography Mission topographic, orthorectified Landsat Thematic Mapper Mosaics and census data with geographical information system methods within 0- to 10-m elevation of the national level. All parameters were examined for coastal cities, coastal districts, settlements, and villages' status. It was found that approximately 7,319 km² of land area lies below the 10-m contour line in Turkey and is, hence, highly vulnerable to sea level rise. Twenty-eight coastal cities, 191 districts, and 181 villages or towns are located below the 10-m contour line in the study area. The findings suggest that the Turkish Ministry of Environment should declare new areas protected and develop special environmental programs at the national level.     

塔里木盆地北部寒武纪海平面变化研究

在以往的沉积学研究中，常常用剖面中的相对水深变化来讨论海平面的变化规律。本文通过对塔里木盆地北部寒武纪上超点变化曲线与肖尔布拉克地区寒武系露头剖面中相对水深变化曲线的对比研究发现，上超点变化曲线与相对水深变化曲线具有明显的差异，前者在寒武纪呈持续上升趋势，而后者除早期有一快速上升外，总体呈持续下降趋势，这说明相对水深变化虽与海平面变化存在着本质的联系，但单凭露头剖面中相对水深变化的研究是难以对海平面变化作出正确估价的，还必须综合考虑基底沉降、沉积物供给等多种因素的影响。计算机模拟结果也证实了，在碳酸盐台地的浅水处，当基底沉降速率较低时，无论是海平面上升还是下降时期，相对水深均呈现持续下降趋势。为了能从露头剖面的地层层序中来了解海平面的变化规律，本文应用作者改进后的Ｆｉｓｃｈｅｒ图解和数学方法对肖尔布拉克寒武系剖面进行了海平面变化的重建，结果发现，它们与上超点变化曲线的变化趋势完全一致。这充分说明了海平面变化对沉积层序的控制作用，同时也告诉我们，不能简单地利用露头剖面中的相对水深变化来研究地质历史时期的海平面变化规律。只有在排除了不同沉积背景上基底沉降速率和沉积物供给速率对沉积层序的控制效应后，才能从露头剖面     

Sea-level fluctuations and the geometric variability of tide-dominated sandbodies

This paper presents examples of various large tidal sandbodies from the Eocene Roda Sandstone in the southern Pyrenees and the Late Pleistocene and Early Holocene in the East China Sea. An attempt is made to summarize the geometric variability of these large tidal sandbodies in relation to the sediment supply and tidal discharge of the depositional system. Transverse sand bars were developed in low-sinuosity, high-gradient channels with high influxes of coarse sediments and water from fluvial systems. Tidal point bars were formed in meandering low-gradient estuarine channel where tidal influence was stronger and sediment was finer than those of the transverse sand bar. A tidal delta complex was built up at the estuary mouth with an abundant sediment supply and an increased tidal discharge. Tidal sand ridges were formed when relict fluvial or deltaic sands were eroded and reworked by strong tidal currents during subsequent sea-level rise.

Since the sediment supply and the tidal discharge of the depositional system were closely related to the eustatic sea-level change and basin subsidence, i.e. the relative sea-level change, special attention will be given to the relationship between geometric variability of tidal sandbodies and the sequence stratigraphic framework in which various sandbodies occurred. Three orders of eustatic sea-level fluctuations can be recognized. The third-order eustatic sea-level cycle, together with basin subsidence, controlled the development of systems tracts and the occurrence of different tidal sandbodies, such as estuary and tidal flat facies during the late stage of a LSW systems tract (type 1 sequence) or a SM systems tract (type 2 sequence); tidal point bar facies, tidal delta facies or tidal sand-ridge facies during a TR systems tract; estuary facies during an early HS systems tract; and fluvial sand bar facies in a late HS systems tract and the early stage of a SM or LSW systems tract. There are also the fourth-order and fifth-order eustatic fluctuations, which are superimposed on the third-order eustatic changes and have important control on the build-up, abandonment and preservation of composite and single tidal sandbodies, respectively.

Since the deposition of tidal sandbodies is very sensitive to eustatic sea-level changes, recognition of various tidal sandbodies is important in sequence stratigraphy analyses of sedimentary basins and in the facies prediction of clastic sediments in basin modelling.