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1.
Daniel Mikeš 《Central European Journal of Geosciences》2009,1(4):463-471
In this work I use the numerical model TAO to study the evolution of the Bureba escarpment, sitting at the watershed between Duero and Ebro Basins and draining into the Rioja Trough. Facies correlation across this area is troublesome through lack of age-dates and therefore timing of tectonosedimentary events is controversial. Numerical modelling should shed some light on the evolution of this area. To that end I have run homogeneous and heterogeneous models for a range of values of erodability, runoff and elastic thickness. The models demonstrate that the tilting of the NE Duero could have resulted from isostatic compensation to erosion in the Rioja Trough and that the Bureba escarpment is a natural barrier to erosion preventing escarpment retreat for at least the next 1 My. 相似文献
2.
Coastal processes and environmental hazards: the Buenos Aires (Argentina) and Venetian (Italy) littorals 总被引：1，自引：0，他引：1
Jorge Pousa Luigi Tosi Eduardo Kruse Dardo Guaraglia Maurizio Bonardi Andrea Mazzoldi Federica Rizzetto Enrique Schnack 《Environmental Geology》2007,51(8):1307-1316
The Buenos Aires (Argentina) and Venice (Italy) coastlands have experienced significant saltwater contamination of the phreatic
aquifer, coastal erosion, hydrodynamic changes and relative sea level rise processes due to natural and man-induced factors.
These factors expose coastal areas to morpho-hydro-geological hazards, such as soil desertification, frequency and degree
of flooding, littoral erosion, and the silting of river mouths and channels. Man-made interventions and actions, such as beach
mining, construction of coastal structures and exploitation of aquifers without an adequate knowledge of the hydrology setting
and an adequate management program, worsen these natural hazards. Uncontrolled human activity induces environmental damage
to the overall coastal plains. The coastal plains play an important role in the social/economic development of the two regions
based on land use, such as agriculture, horticulture, breeding, and tourism, as well as industry. Results of investigations
on saltwater contamination, sea level rise and morphological changes recently performed in these two coastal areas are presented
here. 相似文献
3.
Shirin Mohammadkhan Hasan Ahmadi Mohammad Jafari 《Arabian Journal of Geosciences》2011,4(1-2):331-338
Soil erosion is the dominating factor of damaging roads in Iran. Roads are a critical component of civilization. Developing and maintaining the economic activity that is vital for the quality of modern life would be difficult without roads. Accelerated erosion and increased sediment yields resulting from changes in land use are critical environmental problems, and one of the important changes is road construction. Construction and condition of roadways are associated with direct and indirect impacts on soil erosion. This paper presents the relationship between soil erosion and some characteristics such as distance to roadway, slope, and parent material in Latian Watershed, Tehran Province, Iran. Soil erosion map was interpreted using aerial photos and GIS technology. Buffer zones, subdivided into 12 strips, each 0.2 km wide, which were located alongside roadway. The distribution patterns of various types of erosion were also identified by GIS by overlaying road buffer strips and soil erosion map. The results show that soil erosion landform such as land slide, badland, bank erosion, channel erosion, etc. found in buffer zones along both sides of roads. 相似文献
4.
The USA Clean Water Act requires the development of a total maximum daily load (TMDL) when Minnesota’s water quality standard
for turbidity is exceeded; however, regions underlain with fine-grained lacustrine deposits yield large natural background
loads of suspended inorganic sediment. A review of hydrogeologic pathways was conducted along with the statistical analysis
of geomorphic metrics, collected at 15 sites with varying drainage areas in the upper Nemadji River basin, northeastern Minnesota.
Regression analysis indicated a strong linkage between bankfull cross-sectional area and drainage area. Dimensionless geomorphic
metric ratios were developed to predict channel evolution potential and associated channel erosion risk. Sites located in
drainage areas less than 2 km2 had low erosion risk and showed a correlation between channel slope and relative roughness (D
84/mean bankfull channel depth, 88%). A principal components analysis explained over 98% of the variance between sites and indicated
five important channel shape metrics to predict channel erosion: bankfull width, bankfull depth, maximum depth, cross-sectional
area, and valley beltwidth. Mass wasting of cohesive stream channel sediment was influenced by groundwater discharge and produced
turbid waters in the upper Nemadji River. 相似文献
5.
This work presents the results of a beach-monitoring program carried out in the Bay of Cadiz (SW Spain), which consists of
urban, natural and nourished beaches. In the present study, 24 topographic profiles have been monthly monitored during the
1996–1998 period, in order to draw the morphodynamic behavior of this coast and the general characterization of short-term
coastal trends. This way, total volumetric budgets have been calculated for each beach profile in order to group beaches in
different erosive/accreting sectors. Studied beaches recorded both erosion and accretion: the greatest accretionary trends
have been observed at Aguadulce, La Costilla and Rota beaches, with values ranging from 30 to 70 m3/m. The largest erosion episodes have been recorded in the southernmost end of Valdelagrana spit, with values over 50 m3/m, and in Rota and Vistahermosa, after nourishment works. Main erosion and accretion pathways have been related to the existence
of natural and human structures, which blocked the longshore drift suggesting the existence of littoral cells. 相似文献
6.
原地生成宇宙成因核素测年技术思考(四):核素浓度年份化数列累加方法探讨 总被引：1，自引：0，他引：1
原地生成宇宙成因核素测年技术中,计算核素浓度的传统通用等式假设了地表侵蚀速率(参数ε)及样品的位置在暴露期间保持不变,从而简化了计算过程。然而这种假设可能并不符合复杂地质背景的实际情况,从而造成计算结果误差较大,与其他测年方法结果也难以相互比较和匹配。本文利用将核素总浓度按年份分解为每年生成的浓度,经衰变和侵蚀的综合影响后至今剩余的浓度(称为年份净剩余浓度),组成数列累加的办法,分别推导了地表样品在高程以及侵蚀速率变化情况下的核素浓度计算等式。在此基础上,给出了地表生成速率和侵蚀速率逐年变化情况下的通用浓度年份化累加等式。最后讨论了传统浓度计算等式中的参数ε(侵蚀速率)的地质意义,明确了ε是一个积分中值,并不代表暴露期间的算术平均侵蚀速率,而是每年的侵蚀速率以自然指数加权的复杂方式(即T年前的那一年的生成浓度将乘以e-(λ+ρεΛ)(T-1))影响到样品的最终浓度值。 相似文献
7.
双核素稳态侵蚀岛投影是原地生成宇宙成因核素测年技术中判断样品是否具有复杂暴露历史和估计侵蚀速率的常用方法。暴露、侵蚀、埋藏和再暴露的投影图可依据传统核素浓度计算等式利用计算机编程绘出。利用新推出的地表持续抬升与下降过程中样品的核素浓度与生成速率(及加速率)、侵蚀速率及暴露时间的计算等式,对其26Al/10Be浓度比值相对于10Be浓度/10Be生成速率比值投影分别进行了计算机模拟,发现下降样品的投影可高于或右偏于稳态侵蚀岛,而抬升样品的投影仍然在稳态侵蚀岛内。利用持续地表下降,可以解释已往文献数据中一次性暴露样品投影高于或右偏于稳态侵蚀岛的"不合理"现象,而持续抬升对投影结果的影响类似于侵蚀,因此如果忽略抬升,计算的暴露年龄结果将偏小。 相似文献
8.
Djouher Saadoud Mohamed Saïd Guettouche Mohamed Hassani Francisco José Martin Peinado 《Arabian Journal of Geosciences》2017,10(16):363
Wind-erosion risk is a challenge that threatens land development in dry-land regions. Soil analysis, remote sensing, climatic, vegetal cover and topographic data were used in a geographic information system (GIS), using multi-criteria analysis (MCA) to map wind-erosion risk (Rwe) in Laghouat, Algeria. The approach was based on modelling the risk and incorporating topographic and climatic effects. The maps were coded according to their sensitivity to wind erosion and to their socio-economic potential, from low to very high. By overlapping the effects of these layers, qualitative maps were drawn to reflect the potential sensitivity to wind erosion per unit area. The results indicated that severe wind erosion affects mainly all the southern parts and some parts in the north of Laghouat, where wind-erosion hazard (Hwe) is very high in 43% of the total area, and which was affected mainly by natural parameters such as soil, topography and wind. The results also identified features vulnerable to Rwe. The product of the hazard and the stake maps indicated the potential risk areas that need preventive measures; this was more than half of the study area, making it essential to undertake environmental management and land-use planning. 相似文献
9.
Improper cultivation practices are seriously degrading native forest ecosystems in northern Iran. Hence, the objectives of this study are to compare selected soil properties, runoff amount, erosion and also introducing equations to predict the runoff and soil erosion in three types of land use (forest, garden and cultivated). A simple portable rainfall simulator has been set in 90 random points to create experimental rainfall. Result showed that changes in natural forest led to a significant clay, organic carbon of soil, total N and antecedent soil moisture decrease and sand, pH and bulk density increasing. The rainfall runoff experiments indicate that runoff content of the natural forest soils was 35 % and respectively 38.45 % higher than the garden and cultivated land soils .This result could be related to the higher antecedent soil moisture in natural forest compared with the other land uses. According to the obtained results, garden soil erosion and cultivated land was 1.351 and respectively 1.587 times higher than the forest. The correlation matrix revealed that runoff content was positively correlated with antecedent soil moisture, bulk density and silt, and negatively with soil organic carbon, total N and sand. Also, soil organic carbon, total N, clay and sand showed negative correlation with soil erosion, while there is a positive correlation between erosion and silt, bulk density, pH and antecedent soil moisture. The results of multiple linear regression showed that runoff in forest, garden and cultivated land can be predicted with correlation coefficient of 0.637, 0.547 and 0.624, respectively. The correlation coefficients of 0.798, 0.628 and 0.560 in equations indicate their moderate potential in simulating soil erosion. 相似文献
10.
基于近60年（1959—2018年）系列水下地形资料，研究九段沙成形以来的地貌演化特征和动力成因。结果表明:九段沙1959—1990年处于稳速淤涨、以低滩为主的自然演化状态；近30年（1990—2018年），0 m及以上高滩受植被生长和长江口深水航道治理工程作用快速淤涨，-1~-2 m滩面受干扰程度小、稳速淤涨；近20年（1998—2018年），-3 m及以下低滩受流域减沙和临近的大型涉水工程影响淤涨放缓并由淤积转冲刷，期间流域减沙使得九段沙淤积放缓滩地由低到高向上延伸。未来流域来沙可能进一步下降并维持在较低水平，九段沙将面临-3 m及以下低滩进一步冲蚀，-3 m以上滩地淤积放缓并由低到高逐渐转冲的风险。 相似文献
11.
基于近60年（1959—2018年）系列水下地形资料，研究九段沙成形以来的地貌演化特征和动力成因。结果表明：九段沙1959—1990年处于稳速淤涨、以低滩为主的自然演化状态；近30年（1990—2018年），0 m及以上高滩受植被生长和长江口深水航道治理工程作用快速淤涨，-1~-2 m滩面受干扰程度小、稳速淤涨；近20年（1998—2018年），-3 m及以下低滩受流域减沙和临近的大型涉水工程影响淤涨放缓并由淤积转冲刷，期间流域减沙使得九段沙淤积放缓滩地由低到高向上延伸。未来流域来沙可能进一步下降并维持在较低水平，九段沙将面临-3 m及以下低滩进一步冲蚀，-3 m以上滩地淤积放缓并由低到高逐渐转冲的风险。 相似文献
12.
Stratigraphic records from lake sediment cores and slope deposits on Rapa Nui document prehistoric human impacts and natural environmental changes. A hiatus in sedimentation in Rano Raraku suggests that this lake basin dried out sometime after 4090-4410 cal yr BP and refilled only decades to centuries before AD 1180-1290. Widespread ecosystem changes caused by forest clearance by Polynesian farmers began shortly after the end of this drought. Terrestrial sections show a chronology of burning and soil erosion similar to the lake cores. Although changing sediment types and shifts in the pollen rain suggest that droughts occurred earlier in the Holocene, as yet there is no evidence for droughts occurring after AD 1180-1290. The timing of the agricultural colonization of Rapa Nui now seems well established at ca. AD 1200 and it was accompanied by rapid deforestation that was probably exacerbated by the island's small size, its droughty climate, and the rarity of primeval fires. Detailed records of a large interval of Rapa Nui's ecological history remain elusive due to the drought hiatus in the Rano Raraku sediment record. We find no evidence for a “rat outbreak impact” on Rapa Nui's vegetation preceding anthropogenic forest clearance. 相似文献
13.
Continental erosion is known to be strongly controlled by climate but the way by which geomorphological systems respond to climate change still remains poorly understood. Recent numerical modelling suggests that drainage networks are subjected to strong spatial fluctuations but few studies of natural systems have addressed this phenomenon because of the difficulty of documenting the evolution of erosional landscapes. A detailed field analysis has allowed reconstruction of the past topography of a drainage basin located in southern France where remnants of a past landscape are well preserved. A change from a smooth to a present-day dissected landscape is observed and related to a change in the dominant processes of erosion. This evolution is interpreted in terms of fluctuations in drainage network extent in response to a Holocene increase in precipitation. 相似文献
14.
Relationship of environmental geochemistry to soil degradation in Helwan catchment, Egypt 总被引：1，自引：0，他引：1
Ahmed A. Melegy 《Environmental Geology》2005,48(4-5):524-530
Environmental geochemistry plays an important role in understanding the distribution of major cations (Ca2+, Mg2+, Na+, K+) in Helwan catchment, south Cairo, Egypt. Evaluation of soil mechanical erosion rate, depletion rate, exchangeable rates
of base cations and sodium adsorption ratios are essential for understanding soil degradation problems in the representative
Helwan catchment. Soil erosion is a natural process. It often becomes a problem when human activity causes it to occur much
faster than under natural conditions. The results of the mechanical erosion rate of soil and the exchangeable rates of base
cations are 1845 and 80.3 kg ha−1 yr−1, respectively. The high intensity of the mechanical erosion rate is probably attributed to the high specific surface area
of the studied type of Vertisol, intensive application of fertilizer and industrial activities. Mechanical erosion of soil,
exchangeable rate of base cations and the depletion rate of base cations are almost inexhaustible sources of sodium, and all
these increase the problem of sodic soils and may affect plant productivity in Helwan catchment. 相似文献
15.
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
16.
Large-scale structure of Calamus River deposits (Nebraska, USA) revealed using ground-penetrating radar 总被引：2，自引：0，他引：2
The large-scale (i.e. bar-scale) structure of channel deposits of the braided, low-sinuosity Calamus River, Nebraska, is described using ground-penetrating radar (GPR) profiles combined with vibracores. Basal erosion surfaces are generally overlain by medium-scale, trough-cross-stratified (sets 3–25 cm thick), very coarse to medium sands, that are associated with relatively high amplitude, discontinuous GPR reflectors. Overlying deposits are bioturbated, small-scale cross-stratified (sets <3 cm thick) and vegetation-rich, fine to very-fine sands, that are associated with low-amplitude discontinuous reflectors. Near-surface peat and turf have no associated GPR reflectors. In along-stream profiles through braid and point bars, most GPR reflectors dip downstream at up to 2° relative to the basal erosion surface, but some reflectors in the upstream parts of bars are parallel to the basal erosion surface or dip upstream. In cross-stream profiles through bars, GPR reflectors are either approximately parallel to bar surfaces or have low-angle inclinations (up to 6°) towards cut banks of adjacent curved channels. Basal erosion surfaces become deeper towards cut banks of curved channels. These structures can be explained by lateral and downstream growth of bars combined with vertical accretion. Convex upwards forms up to 0·5 m high, several metres across and tens of metres long represent episodic accretion of unit bars (scroll bars and bar heads). Stratal patterns in channel fills record a complicated history of erosion and deposition during filling, including migration of relatively small bars. A revised facies model for this type of sandy, braided river has been constructed based on this new information on large-scale bedding structure. 相似文献
17.
18.
Multidisciplinary characterization of the middle Holocene eolian deposits of the Elsa River basin (central Italy) 总被引：1，自引：0，他引：1
E.A.C. Costantini S. Priori B. Urban A. Hilgers D. Sauer G. Protano L. Trombino D. Hülle F. Nannoni 《Quaternary International》2009,209(1-2):107
In temperate regions, eolian deposits of different natures are often pedogenically-altered and mixed with underlying sediments. The research reported in this paper identifies for the first time the presence of eolian deposits in soils of central Tuscany and investigates the characteristics and origin. Five relict, polycyclic paleosol profiles were studied. P1 was situated in a natural dust trap, a doline on top of an isolated limestone hill; P2 and P3 were both situated on a limestone plateau, and P4 and P5 on a mid- and foot slope on schist. The profiles were sampled for routine analyses, iron forms, heavy minerals, major and trace elements, and pollen, spores and non-pollen palynomorphs. Undisturbed samples were taken for micromorphological and SEM analyses. Nine soil horizons were sampled for OSL dating. Eolian deposits were dominant or abundant in the first layers of P1, P2 and P3. OSL age determinations of soil horizons deriving from eolian parent material were middle Holocene. Chemical and heavy mineral analyses indicated different possible sources, including bare slopes, alluvial fans and wide channels, coming from the nearby streams that drain the Middle Tuscany ridge and the Mounts of Chianti; marginal contribution of volcanic ashes was only found in P1.The research demonstrated that wind soil erosion accompanied water erosion and colluvial deposition during the middle Holocene in the Elsa River basin. Pollen spectra, in particular, indicated that soil degradation occurred in an environment showing signs of incipient desertification, resulting from an increase of aridity in a land already strongly influenced by humans. Although central Italy is currently considered to be only marginally affected by wind soil erosion, a climate change, which would imply increased arid conditions, could trigger a new cycle of slope denudation, wind erosion and loess deposition. 相似文献
19.
H. M. Yilmaz M. Yakar O. Mutluoglu M. M. Kavurmaci K. Yurt 《Environmental Earth Sciences》2012,66(1):75-81
A fairy chimney is a conical rock formation, typically found in the Cappadocia region of Turkey. The geology of areas where
fairy chimneys exist typically comprise a thick layer of tuff, covered by a thin layer of basalt or other volcanic rocks that
are more resistant to erosion than the underlying tuff. Fairy chimneys are formed where a small cap or boulder of the original
basalt remains, protecting a cone of tuff beneath it from erosion. Eventually, the tuff will be undercut to the extent that
the cap falls off, and the remaining cone is then quickly eroded. In this study, the formation of fairy chimneys in the Cappadocia
region was examined by investigating the surface soil erosion. A study area was selected and then scanned at five different
times by a geodetic robotic total station at 40 cm horizontal and vertical intervals. The volumes of the study area were calculated
from the same height and erosion was calculated from the volume differences indicated by the data. The relationship between
erosion and meteorological data was analyzed, and showed that erosion had increased due to climatic conditions, particularly
from the effect of rainfall. 相似文献