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1.
Nihat Dipova 《Environmental Earth Sciences》2009,59(3):547-560
Cliff erosion and the consequent instabilities present a significant risk to Antalya city (SW-Turkey). Erosional processes
include the chemical action of mixing zone water, the mechanical action of waves, salt erosion and biological degradation.
The rock properties (lithology, stratification, strength, etc.) are the controlling factors to this erosion. The coastal cliffs
of Antalya are composed of tufa type carbonate rocks which occur in a wide range, from collapsible soil to hard rock. The
instability problems of the cliffs of Antalya tufa commonly involve: rock fall, cave collapse, raveling, washout of weakly
lithified tufa, shear failure and secondary toppling. Secondary toppling type instabilities, Culmann type failures and complex
failures, a combination of these two, are widespread on the cliffs. The occurrence of large failures are usually associated
with heavy rainfall as heavy rainfall causes the saturation of pores, increases pore water pressures and reduces the strength
of the rock. Comparison between aerial photographs and topographic maps of different dates, do not provide evidence of considerable
retreat. According to the historical data there has been little or no cliff retreat for 2,000 years. Therefore the erosion
rate of the Antalya tufa cliffs is said to be so very slow that retreat is valid only in a geological timescale. However in
an engineering timescale these cliffs are subjected to instabilities and to local failures causing local retreats. 相似文献
2.
AbstractTwo spectacular cliff lines occur along Australia’s south and west coasts: the Great Southern Scarp (new name) and the Zuytdorp Cliffs. Detailed measurements of their length show that they are exceptionally long and unusually continuous. The Great Southern Scarp is the southern edge of the Nullarbor Plain’s Bunda Plateau; it is cut into shallow marine sediments and extends for 820?km. Once a continuous sea-cliff, local uplift has isolated two sections from the ocean, so it now comprises the Bunda Cliffs (210?km of coastal cliff, 180?km of which is uninterrupted cliff line), Hampton Range (inland; 300?km), Baxter Cliffs (160?km of coastal cliff) and Wylie Scarp (inland; 160?km). The Zuytdorp Cliffs are coastal cliffs cut into eolianite, and extend for 210?km with an uninterrupted section of 120?km. The length of the Great Southern Scarp and the Zuytdorp Cliffs results from an unusual combination of circumstances. They are both composed of poorly jointed, relatively homogenous biogenic calcarenites, presented to high-energy ocean waves by regional uplift. The carbonates are sufficiently well cemented to maintain a steep vertical cliff face, but susceptible to disintegration under direct wave attack. Cliff retreat has been fairly uniform because of the broad spatial scale of both lithology and erosion. The arid climate, absence of nearby non-karstic catchments and karstic nature of the cliffs’ hinterlands has discouraged integrated drainage development, so no significant fluvial systems dissect the cliffs; this is a key factor in cliff edge preservation. In the case of the Great Southern Scarp, these processes have formed the longest continuous cliff line in Australia and probably the world. Referenced against criteria from Australia’s National Heritage List, the cliffs have potentially international/national levels of significance for the rarity of their scale, their demonstration of landscape evolution, and their spectacular beauty.
- KEY POINTS
Australia’s longest coastal cliffs, the Bunda (SA) and Zuytdorp (WA) cliffs, are equal in length (210?km, within defined confidence levels).
The Bunda Cliffs are part of the Great Southern Scarp (new name), an 820 km-long feature of the Nullarbor Plain that also includes the coastal Baxter Cliffs (160?km in length) and two paleocoastal scarps.
The unusual continuity of the cliff lines results from a landscape history specific to the Australian continent, and the Great Southern Scarp is likely to be unusual on a global scale.
The Great Southern Scarp and the Zuytdorp Cliffs have potentially national and/or international levels significance for geoheritage values in the criteria of events and processes, rarity and aesthetics.
3.
D. Michael Williams 《Geoarchaeology》2004,19(2):167-175
Two massively constructed stone forts exist on the edge of vertical coastal cliffs on the Aran Islands, Ireland. One of these, Dun Aonghusa, contains evidence of occupation that predates the main construction phases of the walls and broadly spans a time interval of 3300–2800 yr B.P. The other fort, Dun Duchathair, has been termed a promontory fort because its remaining wall crosses the neck of a small promontory marginal to the cliffs. Estimates of past rates of marine erosion in this part of Ireland may be made both by analogy with studies in other areas and comparison with present day rates of marine erosion. A working model for erosion rates of approximately 0.4 m of coastal recession per annum is suggested. By applying this rate to the cliffs of the Aran Islands, it can be shown that, assuming a construction date of approximately 2500 yr B.P. for these forts, they were originally built at a considerable distance from the coastline. Thus Dun Duchathair was not a promontory fort. The earliest recorded habitation at Dun Aonghusa, dated to the middle of the Bronze Age, was, therefore, at some distance inland and not on an exposed 70 m high cliff on the edge of the Atlantic Ocean. © 2004 Wiley Periodicals, Inc. 相似文献
4.
Cai J.T. Ladd 《Proceedings of the Geologists' Association. Geologists' Association》2021,132(3):269-283
Centuries of coastal development has led to the loss of saltmarsh extent worldwide. As marshes are shrinking, scientific understanding of marsh expansion and erosion processes is growing. Coastal managers are also recognising the importance of marshes for flood protection, carbon sequestration, and pollutant filtering. Considerable effort is now being made to conserve saltmarshes. However, the rapid integration of science in policy remains an obstacle for ensuring successful conservation outcomes. This review explores how advances in the understanding of coastal dynamics, and the evolution of coastal management thinking, are shaping saltmarsh conservation policy in Great Britain. Saltmarsh management has shifted from reclamation, to protection, to restoration throughout the 20th and 21st centuries as calls for nature conservation grew and the importance of ecosystems in coastal erosion risk management became apparent. Studies have revealed that marshes cycle between expansion and erosion phases as part of their natural evolution, governed by processes acting across a range of spatial and temporal scales. Understanding which processes drive long-term marsh change provides an opportunity for coastal managers to undertake targeted intervention for positive conservation outcomes. The inherently dynamic nature of marshes also raises significant challenges in forecasting the long-term value provided by a given marsh. Challenges remain in the monitoring and management of sediment supply and transport, and the effective engagement with stakeholders during habitat protection and creation schemes, which are key to achieving marsh conservation goals. 相似文献
5.
Neelima Thankappan Noujas Varangalil Thomas Kachapally Varghese Kurian Njaliplackil Philipose 《Natural Hazards》2018,90(3):1177-1199
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
6.
This paper deals with the coastal erosion processes and the related problems around the city of Alexandroupolis, NE Aegean
Sea, N. Greece. The area is very fast developing, as the city is an important port and a summer resort center in SE Balkans,
and will become soon a transportation and energy center, as well. The coastline under study exhibits an east–west orientation
and has a length of more than 50 km. The spatial distribution and the characteristics of the changes in the shoreline were
studied by comparing old and new air photographs and topographic maps, as well as through repeated series of field observations
and local measurements regarding the erosion process. From these studies it was concluded that the greater stretch of the
western part of the coast, under consideration, is of moderate to high relief, with a considerable participation of coastal
cliffs. It consists of conglomerates of varying granulometry and consistency and is under moderate to severe erosion process.
The erosion phenomena in the western part of the coast may be attributed, primarily, to strong S, SW winds, blowing in the
area and to trapping of sediments by Alexandroupolis’ port breakwaters; the port stops or/and diverts the sediments to the
open sea; and to the east to west longshore sea current, prevailing in the area. The eastern stretch of the coast is a plain
area, formed by sandy–silty sediments; being a part of the river Evros’ Delta, it is under deposition and accretes seawards.
The majority of the coasts under consideration are classified as coasts of high wave energy potential. Hard structures, as
shore protection measures, have been constructed in some places, but they were proved, in rather short time-period, ineffective
and suffered extensive failures. Thus, it is argued that for a long-term cost-effective tackling of the various erosion problems
on any stretch, priority must be given to soft engineering measures; although, certain hard measures, carefully selected and
locally implemented, can contribute to forming a rational combination of protection/mitigation measures. Besides, the development
pressures in the coastal zone have to be confronted, in a sustainable way, through new integrated coast management regulations. 相似文献
7.
A. V. Tevelev 《Moscow University Geology Bulletin》2014,69(1):17-27
The morphology of alluvial terraces, as well as the facial composition of their sediments, is controlled by a number of factors, whose relative importance continues to be difficult to understand. Detailed studies of river valleys provide models of alluvium development, which differ rather strongly from existing models that postulate regular and universal changes in alluvium composition and structure in the course of its accumulation and further transformation of depositional bodies into a terrace. Based on examples from South Ural river valleys we propose a model of an “upward unsealing terrace,” which forms as a result of above-the-flow (tunnel) erosion. 相似文献
8.
Coastal cliff erosion is a problem in many coastal areas. However, often only very limited data are available to quantify the rates of recession for the development of coastal management strategies. In the soft flysch deposits of the Waitemata Group, Auckland, New Zealand, coastal cliffs are associated with shore platforms. Two models exist for the profile evolution of shore platforms and associated cliffs: the first suggests that an equilibrium profile develops in response to erosive processes, and this profile subsequently migrates landward; the second model suggests that the seaward margin of the shore platform is relatively static, and the profile extends landward through a combination of cliff recession and platform lowering. Physical simulations and field measurements for mudstone and limestone lithologies indicate that the second model is more likely for soft flysch deposits. A eustatic sea-level curve for the Weiti Estuary, Auckland, suggests that up to 7120 ± 70 years have been available for shore platform development since sea level reached the present seaward margins of shore platforms. Shore platform widths were measured using GPS at two sites in Waitemata Group rocks: the North Shore of Auckland; and the southern side of the Tawharanui Peninsula, North Auckland. The long-term cliff recession rates estimated from shore platform widths (1.4 ± 0.1 to 14.3 ± 0.1 mm y− 1) are consistent with the lower end of the average range of cliff top and face recession rates published for Waitemata Group rocks using different methods (11–75 mm y− 1), and in agreement with cliff base recession estimates (3.5 mm y− 1). Shore platform widths were qualitatively related to the rock mass characteristics of the associated cliffs, and therefore platform widths could provide a method of identifying regions of potential hazard. 相似文献
9.
Products of marine processes occupy a considerable vertical range, which varies along the shore. Extreme waves can both cause erosion and form depositional structures up to several metres above the high tide mark. Temporary supra-elevation of water level by surge or wave set-up shifts effects upward. The preservation potential of products of extreme storms is relatively high, when compared to those associated with more frequent events. The level to which coastal landforms develop depends upon the conditions under which they form; thus sand beach ridges which are related to fairweathcr periods have a restricted height range when compared to gravel beach ridges building up under extreme storms. The varied coastal scenery of eastern Ireland provides many examples of storm-related products (barriers. cliffs, platforms, etc.). They have been related to a latc-Holocene eustatic sea level or even a partly isostatically controlled raised late-Holoccne sea level, but both elevations and apparent tilts can be explained by longshore variations in waves, tides and surges. Such an explanation is more consistent with other studies of latc-Holocene coastal evolution around the Irish Sea basin. 相似文献
10.
Arkin Yaacov Karnieli Arnon Issar Arie Mtz.-Esparza Javier Diaz 《Environmental Geology》1986,8(4):185-192
Accelerated erosion of a desert cliff due to uncontrolled sewage water disposal was investigated at the Sede Boqer Campus
in the Negev, Israel An erosional cirque formed by this water was studied as a model simulating natural processes. The cliffs
consist of loess and conglomerate underlain by soft marl, clay, and chalk.
The rate of erosion is of the order of 5%–8% of the volume of water discharged. The rate of incision ranges from 10 2 to 13.3
m/yr and is several orders higher than that expected under normal rainfall conditions
The introduction of this new hydrological factor resulted in a severe disturbance of the morphological balance in the vicinity
of the cliffs, accelerated erosion, and generated circular slides 相似文献
11.
Per Möller Christian Hjort Svante Björck Jorge Rabassa Juan Federico Ponce 《Quaternary Research》2010,73(3):521-534
Isla de los Estados is a mountainous island southeast of Tierra del Fuego, in southernmost South America. Its central and eastern parts have an alpine topography, transected by U-shaped valleys, small, partly over-deepened fjords, and a multitude of abandoned cirques, all associated with extensive former local glaciations. Traces of glacial erosion generally reach 400–450 m a.s.l., and above that trimline a distinct sharp-edged nunatak derived landscape is present. The westernmost part of the island has a lower, more subdued topography, reflecting its “softer” geology but possibly also over-running and erosion by mainland-derived ice streams. The present study concentrated on glacigenic sediment sequences exposed along coastal erosional cliffs. A combination of OSL and 14C datings show that these sediments mostly date from the latest (Wisconsinan/Weichselian) glacial cycle, i.e. from the last ca. 100 ka with the oldest (glaciolacustrine) deposits possibly as old as 90–80 ka. The upper parts of overlying tills, with associated lateral and terminal moraines from glaciers that expanded onto an eustatically exposed dry shelf north of the island, date from the last global glacial maximum (LGM). Radiocarbon ages of peat and lake sediments indicate that deglaciation began 17–16 cal ka BP. 相似文献
12.
Use of LIDAR in landslide investigations: a review 总被引：13，自引：0，他引：13
Michel Jaboyedoff Thierry Oppikofer Antonio Abellán Marc-Henri Derron Alex Loye Richard Metzger Andrea Pedrazzini 《Natural Hazards》2012,61(1):5-28
This paper presents a short history of the appraisal of laser scanner technologies in geosciences used for imaging relief
by high-resolution digital elevation models (HRDEMs) or 3D models. A general overview of light detection and ranging (LIDAR)
techniques applied to landslides is given, followed by a review of different applications of LIDAR for landslide, rockfall
and debris-flow. These applications are classified as: (1) Detection and characterization of mass movements; (2) Hazard assessment
and susceptibility mapping; (3) Modelling; (4) Monitoring. This review emphasizes how LIDAR-derived HRDEMs can be used to
investigate any type of landslides. It is clear that such HRDEMs are not yet a common tool for landslides investigations,
but this technique has opened new domains of applications that still have to be developed. 相似文献
13.
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15.
Soil erosion by water is a significant problem in arid and semi-arid areas of large parts of Iran. Water erosion is one of the most effective phenomena that leads to decreasing soil productivity and pollution of water resources; especially, in the Mazayjan watershed in the southwest of Fars Province gully erosion contributes to the sediment dynamics in a significant way. Consequently, the intention of this research is to identify the different types of soil erosion processes acting in the area and to assess the process dynamics in an integrative way. Therefore, we applied GIS and satellite image analysis techniques to derive input information for the numeric models. For sheet and rill erosion the Unit Stream Power-based Erosion Deposition Model (USPED) was utilized. The spatial distribution of gully erosion was assessed using a statistical approach, which used three variables (stream power index, slope, and flow accumulation) to predict the spatial distribution of gullies in the study area. The eroded gully volumes were estimated for a 7-year period by fieldwork and Google Earth high-resolution images. Finally the gully retreat rates were integrated into the USPED model. The results show that the integration of the SPI approach to quantify gully erosion with the USPED model is a suitable method to qualitatively and quantitatively assess water erosion processes. The application of GIS and stochastic model approaches to spatialize the USPED model input yields valuable results for the prediction of soil erosion in the Mazayjan catchment. The results of this research help to develop an appropriate management of soil and water resources in the southwestern parts of Iran. 相似文献
16.
Curtis R. Olsen Ingvar L. Larsen Patrick J. Mulholland Karen L. Von Damm Jacqueline M. Grebmeier Linda C. Schaffner Robert J. Diaz Maynard M. Nichols 《Estuaries and Coasts》1993,16(3):683-696
Studies have shown that many chemically-reactive contaminants become associated with fine particles in coastal waters and that the rate, patterns, and extent of contaminant accumulation within estuarine systems are extremely variable. In this paper, we briefly review our findings concerning the accumulation patterns of contaminants in several estuarine systems along the eastern coastline of the United States, and have applied a well-established concept in geology, that is “an equilibrium profile,” to explain the observed large variations in these patterns. We show that fine-particle deposition is the most important factor affecting contaminant accumulation in estuarine areas, and that accumulation patterns are governed by physical processes acting to establish or maintain a sediment surface in dynamic equilibrium with respect to sea level, river discharge, tidal currents, and wave activity. Net long-term particle and particle-associated contaminant accumulations are negliglible in areas where the sediment surface has attained “dynamic equilibrium” with the hydraulic regime. Contaminant, accumulation in these areas primarily occurs by the exchange of contaminant-poor sedimentary particles with contaminant-rich suspended particles during physical or biological mixing of the surface sediment. Virtually the entire estuarine particulate and contaminant load bypasses these “equilibrium” areas to accumulate at extremely rapid in relatively small areas that are temporally out of equilibriums as a result of natural processes or human activities. These relatively small areas serve as major sinks for particles from riverine and marine sources, and for biogenic carbon formed in situ within estuaries or on the inner shelf. 相似文献
17.
丹霞地貌定义、分类及丹霞作用研究 总被引：3，自引：0，他引：3
丹霞地貌以广东丹霞山最为典型而得名,是一种发育赤壁丹崖群的特殊地貌类型,近年来随着旅游开发不断升温而成为景观地貌学关注的重要对象,但其中一些基本问题长期争论不休。本文从命名地的地质、地貌特征和我国区域地质发展史角度出发,重新厘定了丹霞地貌的定义与分类,强调丹霞地貌的三大基本要素:赤壁丹崖地貌特征、燕山旋回以来陆相红层基础和以流水侵蚀为主的地质营力。西北地区也广泛发育丹霞地貌,一类是黄土覆盖下的古丹霞,另一类是干旱区片流侵蚀和泥乳贴膜的丹霞。丹霞作用是对中新生代陆相碎屑岩经流水侵蚀、重力崩塌和风化剥落等多种地质作用的统称,其产物就是丹霞地貌。岩性控制和崖壁片流垂蚀是丹霞作用的两种特殊机理。红层盆地的沉积相及其岩性差异控制着丹霞地貌的发育及其景观类型,据此在地貌发育的构造、外力和时间三个因素基础上增加了岩性因素。南方典型的红层盆地中,边缘冲积扇相粗碎屑岩地区可经历青年、中年和老年等发展阶段,盆地中央湖泊相泥岩、粉砂岩却没有经历过绝壁陡崖发展阶段。暴雨水流在丹霞崖壁上发生近垂直向下的侵蚀作用叫片流垂蚀作用。其中冲蚀作用形成竖状沟槽、竖状洞穴,涡蚀作用(借助风力吹动发展成垂直崖壁的涡旋)形成圆锥状洞穴、串珠状洞穴,后者使得洞穴沿软弱岩层分布,进一步扩大成扁平状洞穴。这些洞穴形成年代具有垂向一致性,不具有上老下新变化趋势,而在水平方向上,不同部位洞穴的形成年代可能不同。 相似文献
18.
A geomorphologic approach, combined with GIS spatial analysis, was used to investigate a 90-km long coastal sector in Southern Sicily, Italy, affected by important erosive processes. Applied methodology allowed the creation of a database involving a range of coastal characteristics thereby providing helpful information on coastal processes and general sediment circulation patterns. Coastal erosion, mainly linked to the construction of ports and harbours, has been locally mitigated by the construction of solid structures which themselves generate significant environmental stress in downdrift areas. In recent times, several nourishment projects have been planned to solve existing erosive problems, yet there is still a lack of a general erosion management plan based on the installation of port and harbour by-passing systems and including the phasing out of current beach cleaning and port maintenance procedures that produce a great quantity of sediments. 相似文献
19.
《Geoforum》2017
This paper uses pork as a lens on China’s rural transformations. Taking the industrialization of pig farming in the reform era as a trace on broader processes of social and environmental change, it advances three arguments. First, the massive increase in pork production and consumption since 1978 has been propelled by an industrial meat regime. A party-state led and agribusiness-operated regime, it articulates modernist notions of meat-as-progress with the relentless drive for capital accumulation. Second, using Marx’s concept of metabolic rift, the paper examines how processes of concentration in the industrial meat regime are at the same time processes of separation. This dialectical approach highlights the contradictions inherent in ongoing attempts to disembed capitalist production from biological and social relations. Finally, while official party-state discourse conceptualizes “the rural” as a production base for surplus value, and/or as a site for preserving environmental integrity, the paper’s analysis reveals a further unofficial recasting of the rural: in the process of agroindustrialization, the rural is also a sink for offloading capitalist crises. Between the rivers of manure that flow from industrial livestock operations and contaminate rural waterways; the loss of soil nutrients and food calories in the inefficient conversion of grains and oilseeds into industrial meat; the erosion of agricultural knowledge and practice that accompanies the dispossession of China’s farmers; and the shifting values of pigs, pork, and manure, this is a system that “wastes” the rural in service of capital. 相似文献
20.
A composite fall-slippage model is proposed in this study for the Tertiary sedimentary coastal cliffs of Varkala in the western coastal tract of Peninsular India which are retreating landwards due to the combination of several factors. The fall model in the present study accounts both spring seepage and wave action, resulting in undercutting and this fall affects only the topmost laterite and the just below sandstone in the cliff. Slippage in this area affects all the litho-units and hence the geologic characteristics of all the litho-units are considered for developing the slippage model. This mathematically derived model can be used in other cliffs exhibiting the same morphology as well as the one controlled by the same influencing factors. This model differs from other models in incorporating multi-lithounits as well as multi-notches. Varkala cliffs form a part of the aspiring geopark in the Global Geopark Network and hence a study on the cliff recession is a pressing requirement. 相似文献