共查询到20条相似文献，搜索用时 406 毫秒
1.
基于地形动力学的海滩裂流安全性评价 ——以三亚大东海为例 总被引：1，自引：0，他引：1
文章基于海滩地形动力学模型建立了海滩安全性评价方法,认为低潮沙坝/裂流海滩类和沙坝类海滩出现裂流概率最大,沙坝消散类和有裂流的低潮台地类海滩裂流风险中等,没有裂流的低潮台地海滩、没有沙坝的消散海滩、超消散型、完全反射型海滩裂流风险很小。以三亚大东海为例,利用该评价方法分析了海滩溺水事故频发的原因,结果显示：1）该海滩状态以沙坝型和低潮沙坝/裂流海滩型为主,属于高风险海滩,此结论与当地救生实践吻合;2）该海滩溺水事故发生的根本原因为裂流危险性高,故容易发生溺水事故。 相似文献
2.
The scope of empirical environmental justice (EJ) research has expanded beyond hazards exposure to scrutinize social inequities in access to amenities, but no prior study has examined the EJ implications of public beach access. Furthermore, quantitative research on white privilege is very scarce. To address these knowledge gaps, our study examines racial/ethnic and socioeconomic inequities in access to public beaches in the Miami metropolitan statistical area, Florida. Public beach accessibility is modeled with an innovative geospatial approach that involves population weighted distances to beach access sites. To assess EJ implications of public beach access for various racial/ethnic and socioeconomically vulnerable groups, spatial regression models are estimated using census tract-level data. Results indicate that beaches are more accessible to neighborhoods with a higher proportion of non-Hispanic Whites, while neighborhoods with higher percentages of Hispanics and socioeconomically disadvantaged residents have limited access. This study demonstrates the importance of assessing white privilege and access to environmental amenities in EJ research to better understand social inequities. 相似文献
3.
Dan Bowman 《自然地理学》2013,34(1):34-46
Seven subaerial, low energy beaches in the SE Mediterranean were surveyed biweekly for 13 months. Beach level data were computer-processed and plotted as time-series profile diagrams that differentiated the subaerial beach into three basic subenvironments: backshore, berm, and swash-zone. Heterogeneous seasonal trends in beach sand budget, erosion/accretion patterns, occurrence of ridges and berm-crests, and in pollution by seaborne tar were observed. The profile stations also showed very different degrees of seasonality, although located along similar beaches. Local beachrock protection, when evident, effectively masked seasonality by significantly lowering beach dynamics. Biweekly, seasonal, and annual fluctuations of the beach sand-budget were computed. Average annual net sand flux at the seven beaches was 66 m3/m of beach front, though wide variations occurred. Annual changes in the sand budget along the study area exceeded volumetric changes within the profile, indicating longshore sand transfer. Synchronism of beach behavior prevailed only at the seasonal level. However, intra-seasonal fluctuations for the different profile stations were out of phase, indicating poor synchronism of beach response due to longshore movement of rhythmic topography. Profile changes were thus often unrelated to concomitant wave-climate changes. The overall heterogeneous beach response was in sharp contrast to the identical wave climate, similar bathymetry, and sedimentology of the studied beaches. 相似文献
4.
The configuration of equilibrium beach profile in South China 总被引：3，自引：0，他引：3
To understand the evolution and stability of beaches, prediction of the equilibrium beach profile (EBP) is theoretically and practically important. In the present paper, a new equation, h = AeBx + C is developed to predict the change in beach profile for sections above the water level and the adjacent nearshore portions. Moreover, fractal analysis is applied to predict types of EBP for the first time using the field data collected from Liao Zuikou and Nanwan beaches, South China. Three types of EBP termed Upward-concave EBP (U-EBP), Downward-concave EBP (D-EBP) and Medium-characteristic EBP (M-EBP), are given for the studied region of South China. 相似文献
5.
D. S. Houghton 《The Australian geographer》1989,20(2):173-184
The recreational use of metropolitan beaches is an important but neglected aspect of recreational research in Australia. This paper discusses the results of a survey of beach use in the Perth metropolitan area and also examines travel patterns associated with beach usage. The most popular beaches draw people from throughout the metropolitan area and many people are prepared to travel relatively long distances to visit a particular beach. However, although a distance‐decay effect is apparent, there is little relationship between the pattern of trip generation in Perth and either demographic or status differences between suburbs. It is suggested that further research should focus on temporal aspects of beach usage. 相似文献
6.
Karl F. Nordstrom 《自然地理学》2013,34(2):177-196
This study compares the cyclic and seasonal geomorphic responses of oceanside and bayside beaches on Sandy Hook Spit, New Jersey. It was hypothesized that the different nature of onshore wind regimes at bayside and oceanside beaches would cause different types of beach change. On the east-facing ocean shoreline, rates of beach change are related to weather patterns associated with the passage of mid-latitude cyclonic storms. Bayside beach change is related to the influence of the prevailing westerlies. Storm erosion and post-storm deposition is more rapid on oceanside beaches. Swell waves occurring between storms rapidly reinstate pre-storm equilibrium conditions. Lower bay-side wave energies occurring between storms have little effect on profile development, and foreshore slopes inherited from previous storms undergo little change. Bayside beaches therefore appear to be more in equilibrium with storm conditions than oceanside beaches. Changes in foreshore slope, beach volume, and beach position associated with individual storm events are compared to seasonal trends to test the applicability of the Hayes cyclic model of beach development to both oceanside and bayside beaches. There is evidence of a cyclic trend of develop-ment on the more exposed ocean sites and seasonal development on the more sheltered bayside sites, which suggests that cyclic development may be causally related to the difference among the energy levels of the storm and nonstorm wave regimes. 相似文献
7.
Rip current warning signs complement lifeguards and flags on many beaches globally to alert beach users to the danger of rip currents and to inform beach users about how to identify and avoid rip currents. Although rip current warning signs, such as the sign distributed by the U.S. National Oceanographic and Atmospheric Administration (NOAA), are an important part of any beach safety program, their effectiveness is unknown. Moreover, we do not know how beach users respond to or perceive the rip-current warnings represented graphically and textually. Here we report on a spatially and temporally randomized survey of 392 beach users from three heavily frequented public beaches in Texas (Galveston, Port Aransas, and Corpus Christi) at the height of the summer beach season in 2012. Beach users were asked to respond to the rip current warning sign developed in 2003–2004 by the U.S. Rip Current Task Force. Nearly half of respondents did not notice any warning sign when approaching the beach. When prompted by enumerators with the Task Force sign, 44.5% of beach users found the sign was “helpful” or “very helpful” to their ability to identify a rip current. However, more than half of beach users had difficulty translating the rip current image into a feature observable while standing or sitting on the shore. Many beach users will respond to a warning sign showing the rip current from the perspective of place, rather than the aerial view representing the ocean as space. This realization guides our specific suggestions for improving the current NOAA warning signs. 相似文献
8.
海南岛的海涂土壤及其开发利用 总被引：2，自引：2，他引：0
根据调查资料和采样分析,作者划分海南岛海涂土壤类型,并就机械组成、养分含量、盐渍化程度、粘土矿物组成等方面阐述海涂土壤特征。根据海涂土壤的性质及其生态环境特征进行开发利用,宜以海水养殖和晒盐为主,其中海水养殖可分为8个区。 相似文献
9.
Coastal planform studies are a relevant initial stage before launching detailed dynamic field experiments. The aim of this study is to define the planform characteristics of 72 Catalan pocket beaches, natural and man-made, and to determine their sheltering effect, embaymentization and their status of equilibrium. Planform measurements were performed on SIGPAC, 1:5000 orthophoto sets and wave climate was provided by Puertos del Estado (Wana model). Planform parameters were applied and coastal planview indexes were determined.The study shows that the Catalan pocket beaches display a wide range of indentation, suggesting that no single structural, tectonic or morphological control dominates their planform. The man-made pocket beaches typically display indentations which are smaller than those shown by natural pocket beaches. Headland spacing and beach area are positively correlated. The more indented bays are, the shorter their beaches become. Low-indented pocket beaches are the widest and the longest ones.Deep indentation contributes towards beach protection and energy dissipation which counteracts rip efficiency and inhibits the formation of mega-rips. Pocket beaches often show gradual and moderate alongshore changes in texture and beach morphology. One third of the Catalan pocket beaches are “sediment starved”, i.e., 60% and more of their embayed shorelines are deprived of beach sediments. Examination of the status of equilibrium demonstrates that most of the Catalan pocket beaches are in an unstable mode, with indentation ratios that are unrelated to the wave obliquity. 相似文献
10.
ABSTRACT Composition and richness of coastal vegetation differs with distance from the water and sheltering by topography. Transition from pioneer beach plants to mature forests is expected to be narrow on low wave energy coasts with a tropical climate favorable to vegetation growth. The goal of this paper is to determine whether vegetation on the beach and foredune will be denser and have a greater number of species and more woody shrubs near the water as wave and wind stresses diminish because of favorable shoreline orientation within a pocket beach. Field data on beach width, beach mobility, dune height, vegetation species, vegetation height and percent vegetation cover were collected in Puerto Rico along six cross-shore transects. Beaches are more stable at transects in the lee of an eolianite barrier and a tombolo. The vegetation gradient there is compressed, with denser, taller, more diverse vegetation and more tree species close to the waterline than at more exposed sites. The lack of mobility of the beaches and dunes and lack of geomorphically significant disturbance events is in contrast to the conspicuous feedbacks between overwash, topography, and vegetation on exposed mid-latitude coasts, revealing the need for more study of low-energy beach environments. 相似文献
11.
《Geomorphology》2006,73(1-2):33-49
Intertidal bar systems are ubiquitous features on wave-dominated beaches in coastal settings with a significant (> 1 m) tidal range. Depending primarily on the wave conditions and the tidal range, and to a lesser extent on the nearshore gradient, they can assume a variety of forms. Slip-face bars represent the most pronounced and dynamic intertidal bar morphology, and are generally found on their own around the mean high tide level. They usually form low on the intertidal beach after storm-induced beach erosion and develop into a berm under prolonged calm wave conditions. Low-amplitude ridges and sand waves represent multiple bar morphologies. The bars occur across the entire intertidal profile and they remain present throughout the year. Multiple intertidal bars tend to be rather subdued and relatively static, especially sand waves, and their origin remains unclear.The morphological response of intertidal bars to changing wave conditions is largely forced: bars build up and migrate onshore under calm waves, and are flattened and may migrate offshore during storms. The morphological response is, however, significantly affected by relaxation time effects and morphological feedback, particularly on beaches with multiple intertidal bars. Despite their morphological differences, the intertidal bar types exhibit pronounced similarities in their morphodynamics. Sediment transport processes and morphological response are principally controlled by the tidal water levels on the beach, because these, together with the offshore wave energy level and the beach morphology, determine the type, intensity and duration of the wave processes operating on the cross-shore profile.It is the dominant importance of tidal water level variations and wave processes in shallow water depths (swash and surf zone bores), rather than wave height variability and deeper water wave processes (breaking and shoaling waves), that constitutes the main difference between intertidal and subtidal bar morphodynamics. 相似文献
12.
海滩状态是一个地形与水动力相互作用的三维地形动力问题.国外对海滩状态的地形动力分类已开展了大量卓有成效的研究工作,既包括波控、小潮、开阔海岸海滩状态的研究,也包括波控、不同潮差海岸海滩类型的研究和岬间海岸海滩类型的研究.文中回顾并概括了自20世纪70年代至今国外在砂质海滩地形动力分类方面代表性的研究工作,这些对于我国的... 相似文献
13.
Beach Profiles surveys and gale climate data were utilised to assess medium timescale beach rotation at four beaches located along the shores of a crenulated embayment within Swansea Bay, Southwest Wales. The proposed Tidal Lagoon is located within this Bay. Results identified a 7 year (1998–2005) record of cyclic summer/winter rotation and a 14 year (1999–2013) record of annual rotation within the subaerial zone on all four assessed beaches. In the absence of headlands to trap sediment it is asserted that the driving force for beach rotation is the presence of Swansea Dockland/Tawe dredged channel complex, Port Talbot Harbour and the Neath dredged channel which form surrogate headlands essentially creating four separate beach systems through restricting sediment by-pass. Seasonal averaged wind and wave variables showed differing correlation with volume changes and cross-correlation results showed that volume variation lagged behind forcing variables by up to six months (i.e. the resolution of the data). This was confirmed by the annually averaged results which showed only subtle correlation. Here volume change in most cases lagged forcing variables by less than one year. Based on correlations, wind direction variability follows closely with volume changes but wind speed, wave period and height are generally opposite. Initial results suggest that the proposed Swansea Bay Tidal Lagoon, located between sediment cells and surrogate headlands, would have little negative effect on subaerial coastal processes. These datasets will be used as a benchmark for monitoring prior to, during and post construction, with results being used to update and inform subsequent strategies. 相似文献
14.
《Journal of Arid Environments》1998,39(3):533-547
Aeolian sand transport on two nourished beaches was related to the fetch of the wind over the beach sand and to surface characteristics. Meteorological and hydrological conditions were recorded for 2 months. The fetch of wind over beach sand was estimated from wind direction, water level, wave height and beach topography. Aeolian sand transport was determined with sand traps. Sediment flux was found to increase with fetch, although this relation was especially affected by the variability in surface characteristics. On one of the beaches sediment supply was limited as a result of shells, forming a lag deposit. 相似文献
15.
The Beautiful China Initiative(BCI)is a plan for the sustainable development of the Chinese nation as well as for China to fulfill the United Nations’2030 Agenda for Sustainable Development.The Chinese government’s“five-in-one”approach provides strategic arrangements for developing the BCI,and President Xi Jinping proposed a timetable and“road map”for the BCI at the National Conference on Ecological and Environmental Protection.Nevertheless,the theoretical basis,evaluation index system,evaluation criteria and effectiveness of the BCI are currently unclear.This paper begins by exploring the basic content of the BCI from narrow and broad perspectives.It regards the theory of human-nature harmonious coexistence and the five-in-one beauty theory as the core theoretical bases of the BCI and constructs a five-element BCI evaluation index system(ecological environment,green development,social harmony,system perfection and cultural heritage)and utilizes the assessment method of the United Nations’Human Development Index to assess scientifically the effectiveness of the BCI in 341 prefecture-level cities.The results show the average BCI index(the Chinese Academy of Sciences Beauty Index)score to be 0.28,which is quite low,while the average scores for the individual element indexes of the ecological environment index,green development index,social harmony index,system perfection index and cultural heritage index are 0.6,0.22,0.29,0.22 and 0.07,respectively.All of these are relatively low values,with relatively large discrepancies in regional development,indicating that progress in the BCI is generally slow and unbalanced.To realize the BCI’s timetable and roadmap to a high quality and high standard,it is suggested that a common system for evaluating the progress of the BCI is developed and promulgated so that dynamic monitoring and phased evaluations can take place;BCI technical assessment standards are compiled and published;BCI comprehensive zoning is undertaken;pilot projects adapted to local conditions are launched in BCI sample areas;and BCI results are incorporated into performance indicators at all levels of government. 相似文献
16.
A photogrammetric and sediment analysis is presented to illustrate the relationship between beach erosion and seacliff recession on Thompson Island, Boston Harbor, Massachusetts. Aerial photographs taken in 1938, 1952, 1963, and 1977 were measured to determine rates of shoreline change around the island. The 39-year average rate of beach erosion is 0.3 m/yr ± 2% with an average rate of cliff recession at 0.2 m/yr ± 2%. Rates of beach erosion between six orientations that reflect principal wave approach to the island were not found to be significantly different (0.05) for the 39-year period. The rank order correlation between beach erosion and cliff recession for these six orientations was moderately well correlated (0.63). To determine possible controls of cliff erosion, 58 sediment samples were collected from glacial cliffs along the shoreline. The textural composition was determined, and then tested with discriminant function analysis. Partial correlation analysis between beach erosion and cliff recession holding a surrogate for sediment size constant improved the rank order from 0.63 to 0.84. The results indicate that coarser-grained cliffs recede at faster rates, but with less erosion occurring on adjacent beaches. Alternatively, finer-grained cliffs recede at slower rates, but with greater erosion occurring on adjacent beaches. 相似文献
17.
John C. Dixon 《自然地理学》2013,34(4):334-343
Relict barrier beaches occur around the margins of many former pluvial lakes in the California desert. In common with modern barrier beaches along ocean coasts, these relict barriers possess geometric and compositional properties indicative of beach-forming processes, notably waves and currents. Because lake waves are a direct response to wind action, past wave climates may in turn be used to infer paleowind regimes. Where beaches of known age occur, wave climates and wind regimes may be invoked for specific time intervals. Using barrier beaches from former Lake Mojave and Lake Manly, this paper explores the extent to which the above theory may be applied to invoke past processes and wind regimes. The data indicate beach emplacement mainly by wave-related accretion and overwash generated by winds similar in direction to those of today, doubtless influenced then as now by topographic corridors. However, textural properties, predicted wave heights and entrainment velocities indicate that sustained southerly winds were probably twice as strong (by a factor ranging from 1.2 to 2.2 or more) and probably more persistent than today, at least towards the close of pluvial conditions. [Key words: barrier beaches, wave climate, paleoclimate, paleowinds, pluvial lakes, Quaternary, California desert.] 相似文献
18.
Questionnaires were completed by 2306 beach users at 19 Welsh beaches with respect to beach selection parameters. The modal group of respondents was female aged 30–39. Beach choice was primarily determined by clean litter-free sand and seawater, followed by safety. Refreshment facilities and beach awards were deemed minor considerations by the public when choosing a beach to visit. Approximately 58 per cent of respondents were aware of beach award and rating schemes. Of coastal visitors interviewed for this paper, 67 per cent rated a beach as 'important' or 'very important' to their holiday, with just 2 per cent replying that they were unimportant. 相似文献
19.
DAVID HUDDART MATTHEW R. BENNETT MICHAEL J. HAMBREY NEIL F. GLASSER KEVIN CRAWFORD 《Polar research》1998,17(1):61-70
Well-rounded gravels are described from moraine-mound complexes, diamicton forefields and modern englacial thrusts at the margins of four glaciers on the northern side of Brøggerhalvøya, northwest Spitsbergen. Their shape charcteristics are compared with modern and fossil glacigenic, modern beach and Early Weichselian beach gravels from this peninsula. The best discriminators of the well-rounded gravels have been found to be the percentage-frequency roundness histograms, the roundness mid-point and roundness range diagrams and the sphericity-roundness plots. It is concluded that the gravels have been derived by englacial thrusting from Early Weichselian or last interglacial beaches in the inner parts of the fjord and in the low level cirques when sea level reached at least 50m a.s.l. and deposited the beach gravels. The discrimination between gravel in basal diamictons, proglacial outwash and modern beaches is difficult as the reworking has resulted in little particle shape change. The potential major problem caused by reworking in the glacial environment is emphasised. especially when clast shape comparisons from modern environments to older sediments are used. 相似文献
20.
开封市黄河滩区土地资源规避洪水风险的安全利用 总被引：2，自引：1，他引：1
基于ArcGIS与ERDAS遥感影像制图软件,利用2007年SPOT2.5m分辨率遥感影像,结合实地调查,详细编绘了开封市段黄河河道边界、开封段黄河滩区土地资源的利用现状。采用1992~2007年最大洪峰时期的TM影像与沿河水文站点的观测资料,提取1992~2007年7个典型日期的河道行洪边缘线,与本底数据叠加,编制了开封段不同常遇洪水流量下滩区淹没范围。按照黄河下游二维水沙数学模型,采用2004年汛后河道大断面资料,计算生成不同流量级大洪水在滩区的可能淹没范围图(淹没区边界)。在此基础上,结合土地资源管理与河道行洪安全性的要求,总结当前黄河下游滩区利用开发的现状与存在问题,制订土地安全利用规避洪险的原则,规划土地安全利用分区,分为临河风险缓冲带、近河宜耕地带、相对稳定利用带(中风险带)和稳定利用带。提出了黄河滩区土地资源合理安全利用的对策。 相似文献