Beach Morphodynamics influenced by an ebb‐tidal delta on the north Florida Atlantic coast          下载免费PDF全文

Peter N. Adams  Katherine Malone Keough  Maitane Olabarrieta 《地球表面变化过程与地形》2016,41(7):936-950

Tidal inlets interrupt longshore sediment transport, thereby exerting an influence on adjacent beach morphology. To investigate the details and spatial extent of an inlet's influence, we examine beach topographic change along a 1.5 km coastal reach adjacent to Matanzas Inlet, on the Florida Atlantic coast. Analyses of beach morphology reveal a behavioral change between 0.64 and 0.86 km from the inlet channel centerline, interpreted to represent the spatial extent of inlet influence. Beyond this boundary, the beach is narrow, exhibits a statistically significant inverse correlation of shoreline position with offshore wave conditions, and has a uniform alongshore pattern in temporal behavior, as determined from empirical orthogonal function (EOF) analysis. On the inlet side of the boundary, the beach experiences monotonic widening (with proximity to the inlet), lacks spatial consistency in correlation between shoreline position and wave conditions, and exhibits an irregular pattern in spatial EOF modes. We augment the field observations with numerical modeling that provides calculations of wave setup and nearshore current patterns near the inlet, highlighting the effects of the ebb‐tidal delta on the assailing waves. The modeling results are verified by a natural experiment that occurred during May 2009, when a storm‐produced sedimentary mass accreted to the lower beach, then subsequently split into two oppositely directed waves of sediment that migrated away from the initial accretion site in the subsequent months. Our results suggest that the ebb‐tidal delta produces a pattern of wave setup that creates a pressure gradient driving an alongshore flow that opposes the longshore currents derived from breaking of obliquely oriented incident waves. The resulting recirculation pattern on the margin of the ebb‐tidal delta provides a mechanism through which the inlet influences adjacent barrier island beach morphology. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

METHODOLOGY: A DEVICE FOR MONITORING SOIL MOVEMENT IN PEATLANDS     

Frederick E. Nelson 《自然地理学》2013,34(3):275-281

Traditional methods of tracking soil movements may be unreliable in soils containing a large proportion of organic matter owing to the composition and mechanical properties of peat. A simple, inexpensive, and reusable “anchored” target can be used to monitor both vertical and horizontal components of soil movement in fibrous peat. The target is unlikely to be affected adversely by flooding, frost heave, or animal disturbance, and is applicable to a wide range of geomorphic problems in peatlands. [Key words: frost heave, peat, peat landforms, soil movement, survey targets.]  相似文献   

径向基神经网络模型在杭州湾北岸岸线变化中的应用     

谢华亮  戴志军  彭伟  张小玲 《上海国土资源》2012,33(2):74-78

基于杭州湾北岸龙泉—南竹港弧形岸段实测岸滩断面与长江入海控制站大通站年输沙量资料,对杭州湾北岸岸线的变化及其趋势进行探讨。研究结果表明：受长江入海泥沙减少以及热带气旋和人类活动作用等影响,近10年来杭州湾北岸岸滩处于侵蚀状态。灰色关联分析进一步揭示,杭州湾北岸不同等深线的进退对长江入海泥沙减少的响应在时间尺度上有一定的滞后。同时,不同等深线的进退亦展现较强的相关性特征。鉴于此,利用大通年输沙量和不同等深线进退的耦合关系,进一步构建了基于长江入海泥沙和杭州湾北岸等深线变化的径向基神经网络岸线预报模型,其中模型输入向量为当年大通站年输沙量和杭州湾北岸-3m、-5m、-8m等深线距离大堤的位置,输出向量为次年0m岸线距离大堤的位置。经检验,构建的径向基神经网络岸线预报模型误差小于20%,可用以预报杭州湾北岸岸线的动态变化。  相似文献   

Horizon scanning for alien predatory crabs: insights from South Africa     

《African Journal of Marine Science》2013,35(2):125-135

Due to the presence of few dominant predators on South African rocky shores, this coastline could be vulnerable to invasion by predatory crabs. This study applied horizon scanning to create an ordered watch list of alien crab species that could establish along this coastline under present-day and future temperature scenarios. This was done by: (i) identifying the species with both an invasion history and a possible pathway to South Africa; (ii) comparing the temperature ranges of the species’ native and introduced distributions to those of each of the four South African ecoregions; and (iii) ranking the species based on their potential ecological impacts. Of the 56 alien predatory crab species known worldwide, 28 species have pathways to South Africa. Incompatible temperature ranges excluded only two species from each ecoregion. Negative ecological impacts in their invaded ranges placed Japanese shore crab Hemigrapsus sanguineus, brush-clawed shore crab H. takanoi and Chinese mitten crab Eriocheir sinensis at the top of the watch list. This study highlights that many alien crab species have the potential to reach South Africa, with most likely to survive. This watch list should be used to support targeted monitoring and so facilitate early detection of these species, should they reach South Africa.  相似文献   

Geometric Integration of Aerial and High-Resolution Satellite Imagery and Application in Shoreline Mapping     

Rongxing Li  Sagar Deshpande  Xutong Niu  Feng Zhou  Kaichang Di  Bo Wu 《Marine Geodesy》2013,36(3):143-159

This paper investigates the geopositioning accuracy achievable from integrating IKONOS and QuickBird satellite stereo image pairs with aerial images acquired over a region at Tampa Bay, Florida. The results showed that the accuracy is related to a few factors of imaging geometry. For example, the geopositioning accuracy of a stereo pair of IKONOS or QuickBird images can be improved by integrating a set of aerial images, even just a single aerial image or a stereo pair of aerial images. Shorelines derived from the IKONOS and QuickBird stereo images, particularly the vertical positions, are compared with the corresponding observations of water-penetrating LiDAR and water gauge stations and proved that differences are within the limit of the geopositioning uncertainty of the satellite images.  相似文献   

Hurricane damage along natural and hardened estuarine shorelines: Using homeowner experiences to promote nature-based coastal protection     

《Marine Policy》2017

Growing coastal populations, rising sea levels, and likely increases in the frequency of major storm events will intensify coastal vulnerability in coming decades. Decisions regarding how and when to fortify estuarine shorelines against coastal hazards, such as erosion, flooding, and attendant property damages, rest largely in the hands of waterfront-property owners. Traditionally, hard engineered structures (e.g. bulkheads, revetments, seawalls) have been used to protect coastal properties, based on the assumption that these structures are durable and effective at preventing erosion. This study evaluates the validity of these assumptions by merging results from 689 surveys of waterfront-property owners in NC with empirical shoreline damage data collected along estuarine shorelines after Hurricanes Irene (2011) and Arthur (2014). The data show: 1) homeowners perceive bulkheads to be the most durable and effective at preventing erosion, but also the most costly; 2) compared to residents with revetments and natural shorelines, property owners with bulkheads reported double the price to repair hurricane damage to their property and four times the cost for annual shoreline maintenance; 3) 93% of evident post-hurricane shoreline damage was attributable to bulkheads or bulkhead hybrids and a higher proportion of surveyed homeowners with bulkheads reported having property damage from hurricanes; and, 4) shoreline hardening increased by 3.5% from 2011 to 2016 along 39 km of the Outer Banks. These results suggest that bulkheads are not meeting waterfront property-owner expectations despite continued use, and that nature-based coastal protection schemes may be able to more effectively align with homeowner needs.  相似文献   

实行海岸线分类保护 维护海岸带生态功能——《海岸线保护与利用管理办法》解读          下载免费PDF全文

潘新春  杨亮 《海洋开发与管理》2017,34(6):3-6

《海岸线保护与利用管理办法》是我国专门针对海岸线管理的首部规范性文件,弥补了我国海岸线管理的空缺。文章简要介绍《海岸线保护与利用管理办法》出台的背景;详细分析海岸线保护与利用管理的重要举措:(1)提出自然岸线保有率控制制度,(2)提出海岸线分类保护制度,(3)实施自然岸线保护与利用的年度计划管理,(4)编制全国和省级海岸线整治修复五年规划和年度计划以及建立全国海岸线整治修复项目库;阐述《海岸线保护与利用管理办法》对海岸线保护的作用与意义;最后对全面加强海岸线保护与利用管理提出建立健全各项配套制度、不断完善技术标准体系以及开展海岸线保护管理专项行动的建议。  相似文献   

渤海湾西侧泥质海岸带全新世岸线的变化与海洋的影响     

王宏  商志文  李建芬  裴艳东  王福  田立柱  范昌福  盛晶瑾  陈永胜  刘会敏 《中国区域地质》2010,(5):627-640

以渤海湾泥质海岸带为例,从形态和地层证据2个方面总结了全新世岸线变化与海洋作用对该地区海岸带发育的影响。中全新世以来千年级别的岸线变迁至少以6次停顿（形成贝壳堤和泥质岭地）和岸进的交替为特征。过去130年间10年级别的岸线变化分为4个阶段,显示了＂小冰期＂结束后随气温上升而发生的岸线自然蚀退是如何逐渐被人类活动（特别是2000年以来的围海造陆）所取代的。全新世海相沉积中发现的9个峰值期和晚全新世的7次风暴驱动事件,表明了研究区泥质海岸带增强的海洋影响。这些结果提供了一条经由地质背景认识现代泥质海岸带过程的途径。  相似文献   

Late Pleistocene to early Holocene lake level and paleoclimate insights from Stansbury Island, Bonneville basin, Utah     

Shela J. Patrickson  Andrea R. Brunelle 《Quaternary Research》2010,73(2):237-246

This paper reports on recent multiproxy research conducted to determine the chronology of lake-level fluctuations recorded in sediments from a natural exposure at a classic Bonneville basin site. Grain size, carbonate percentage, magnetic susceptibility, amount of charcoal, and diatom community composition data were collected from the 16 lacustrine units that compose the 122 cm stratigraphic column in Stansbury Gulch. Trends observed in the measured proxies reveal several significant changes in lake level, and thereby effective moisture, over the approximately 14,500 yr time span represented by the sediments. Results (1) verify the effectiveness of the multiproxy approach in Bonneville basin studies, which has been underutilized in this region, (2) reaffirm the double nature of Lake Bonneville's Stansbury oscillation, (3) suggest a previously undocumented post-Gilbert highstand of Great Salt Lake, and (4) identify possible teleconnections between climate events in the Bonneville basin and events in the North Atlantic at about 20,500 and 7500 ¹⁴C yr BP.  相似文献   

气候变化对北方农牧交错带界线变迁影响的定量探测方法研究   总被引：4，自引：1，他引：3  

史文娇  刘奕婷  石晓丽 《地理学报》2017,72(3):407-419

气候对北方农牧交错带界线变迁的定量影响是目前生态脆弱敏感区对气候变化响应领域的研究热点问题。前人已在气候变化对农牧交错带界线的定性影响方面有较为深刻的认识,但仍缺乏在时间和空间上对气候贡献率进行有针对性的定量辨识。本文利用1970年以来长时间序列的国家气象站点数据和土地利用遥感解译数据,分别提取了基于气候要素和土地利用的20世纪70年代、80年代、90年代和21世纪前10年4个时期的北方农牧交错带界线,通过垂直和水平方向变动探测方法（FishNet）和界线变迁方向变动探测方法（DSAS）对气候界线与土地利用界线的时空变化进行探测,定量分析了不同时期气候对农牧交错带界线变迁影响的贡献率。结果表明,气候与土地利用界线空间分布格局及气候贡献率在不同时期、不同区域差异较大,在西北地区变幅最小,东北地区变幅最大。在大兴安岭东南缘农田控制水源涵养生态功能区西北段以及内蒙古高原东南缘农、林、牧业生态—生产功能区西北段,气候与土地利用界线空间耦合关系最为密切,在该地区基于FishNet方法下水平方向上气候贡献率达10.7%~44.4%,垂直方向上达4.7%~55.9%;基于DSAS方法下气候贡献率为1.1%~16.8%。两种方法探测结果大部分趋于一致,但DSAS方法精度高,适用于小范围精确探测;FishNet方法更简单,适用于精度要求不高、快速直观的统计分析。本研究可为北方农牧交错带内农牧业生产适应气候变化、合理开发土地生产潜力、保护农牧交错带区内生态环境提供科学依据和指导。  相似文献