Frontiers of Earth Science

ISSN 2095-0195

ISSN 2095-0209(Online)

CN 11-5982/P

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, Volume 4 Issue 4

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FEATURE ARTICLE
Rivers in Australia
Brian FINLAYSON
Front Earth Sci Chin. 2010, 4 (4): 375-385.  
https://doi.org/10.1007/s11707-010-0129-y

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As a continent, Australia is unusual. It has a long history of habitation by a relatively small population of Aboriginals with a low technology culture. Just over 200 years ago, in 1788, it was invaded by a technological society from the UK, and the settlers brought with them an understanding of rivers and the landscapes in which they were situated which was quite at odds with the reality of the Australian continent. Australia is a piece of old continental crust derived from the break-up of Gondwana that, unlike other Gondwana continents, has experienced little tectonic modification since the break-up. It is a low relief continent dominated by arid and semi arid climates. Australian river systems have poor slope-channel coupling and poor hydrological connectivity and are characterized by low rates of sediment delivery. The flow of Australian rivers has high interannual variability, two to three times that of comparable rivers elsewhere, and highly variable flood behavior. In this paper, examples are given of particular Australian rivers to illustrate the manner in which the morphological and climatic characteristics of the continent combine to produce some distinctive river systems.

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RESEARCH ARTICLE
Zhidanyuan sluice of Yuan-dynasty, Shanghai area of Yangtze delta: Discussion of its abandonment
Xin WANG, Zhanghua WANG, Zhongyuan CHEN, Jiying HE, Jian SONG
Front Earth Sci Chin. 2010, 4 (4): 386-392.  
https://doi.org/10.1007/s11707-010-0121-6

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The present study examines the rise and fall of the sluice of the Yuan dynasty (1279–1368 AD) unearthed in Zhidanyuan, Shanghai, by means of radiocarbon-dated sediment profiles, sedimentary facies indices and the historical literatures. Magnetic fabric parameters of sediment profiles help reconstruct the tidal creek setting at the sluice site. Our records evidence a fluvially-dominated hydrodynamic setting before sluice construction, but a saltwater intruded setting in the later stage. Magnetic fabric shows a stable flow direction in the upstream of the sluice, implying the fluvial deposition, while scattering flow directions downstream, suggesting interactions between the river flow and tidal currents. It is concluded that the sluice construction was primarily aimed at preventing saltwater intrusion from the Yangtze River mouth, but its operation did not fully fit the high sediment siltation in the channel that occurred after the sluice construction. This weakens significantly the role of sluice operation, leading to its abandonment eventually.

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Settlement relocations in the char-lands of Padma River basin in Ganges delta, Bangladesh
Shafi Noor ISLAM, Shilpa SINGH, Hasibush SHAHEED, Shouke WEI
Front Earth Sci Chin. 2010, 4 (4): 393-402.  
https://doi.org/10.1007/s11707-010-0122-5

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Bangladesh has a unique hydro-geological setting and deltaic floodplain which is jointly formed by the deposition of the Ganges (Padma), Brahmaputra (Jamuna) and Meghna River. The physical characteristics of the geographic location, river morphology and the monsoon climate render Bangladesh highly vulnerable to natural disasters, primarily, floods and cyclones. River flooding has exerted a great impact on the culture and socioeconomic activities. The char people and their settlements in the Padma River channel are under threat due to floods and associated river bank erosion. The excess of water happens during the monsoon season because of widespread flooding that damages char-land settlements, agricultural crops, infrastructure and communication networks. Purba Khas Bandarkhola Mouza of Char-Janajat is largely affected by annual floods, and as a result the char people are displaced frequently from one place to another within and/or outside the char. The dwellers can return to the native char when new land emerges in the river channel after floods. This study has revealed that the displacement of char settlement takes place in almost every 3–5a at Purba Khas Bandarkhola Mouza of Char-Janajat. Our findings shed light on the char flood disaster management and social adaptation plan for settlement development of char livelihood in the Padma River basin in the Ganges delta of Bangladesh.

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A simplified conception model for salt marsh sedimentation rate calculation: Response to changing suspended sediment concentration—A case study of Wanggang salt marsh, Jiangsu Province, China
Aijun WANG
Front Earth Sci Chin. 2010, 4 (4): 403-409.  
https://doi.org/10.1007/s11707-010-0123-4

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Situated at the junction of land and sea, coastal salt marshes are very sensitive to global environmental changes. Existing numerical models simulating the vertical growth of coastal salt marshes are under the conditions of low suspended sediment concentration (SSC), but under high SSC, such as in the Jiangsu coast of China, the models need to be refined. In this paper, based on the mass balance principle, a refined zero-dimensional time-stepped model is applied after considering the average suspended sediment concentration (ASSC). The statistical results of in situ observation data show that there is an obvious positive linear relationship between ASSC and maximum inundation height, and an obvious positive exponential one between inundation time and inundation height. Using the short-term measurement values for the input parameters and incorporating the above-mentioned relationship between SSC and inundation height, the sedimentation rates are calculated, and the results are similar to previous data. In addition, some factors and hydrodynamic processes that were ignored or simplified could influence the calculated value.

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Subsidence of Holocene sediments in the Godavari delta, India
K. NAGESWARA RAO, N. SADAKATA, Vasant SHINDE, A. S. RAJAWAT, AJAI
Front Earth Sci Chin. 2010, 4 (4): 410-416.  
https://doi.org/10.1007/s11707-010-0124-3

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The present study is an attempt to estimate the rates of subsidence in the Holocene sediments of the Godavari delta along the east coast of India. Two boreholes dug at Panangipalli village in the delta revealed Early Historic culture material such as potsherds including Coarse Red ware, Red-Slipped ware, Coarse Grey ware, and Black and Red ware, between 3.5 m and 9.0 m below the surface level. This suggests that the location was a human settlement of Andhra Satavahana period which flourished in the region between 3rd century BC and 3rd century AD. The fossil shells of Anadara sp. recovered from the borehole further downward at 11.5 m below the surface are considered to represent the intertidal swampy/ lagoonal environment. The age of the shells was determined through AMS 14C dating as 6400 cal a BP. The presence of about 2.5mthick intertidal swampy/lagoonal material between 9.0 m and 11.5 m depth, suggests post-depositional subsidence at an average rate of less than 1.0 mm·a-1. However, a higher rate of subsidence of about 2.0 mm to 4.0 mm·a-1 is estimated for the upper 9.0mthick floodplain sediment unit which embeds the Early Historic culture remains. The increased rates of subsidence during the last two millennia when compared to the earlier period in this part of the Godavari delta could be due to anthropogenic activity of deforestation and agriculture leading to accelerated soil erosion in the catchment and increased sedimentation in the delta.

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Analysis of current directions in the bends of an ephemeral river and its geological implications
Barendra PURKAIT
Front Earth Sci Chin. 2010, 4 (4): 417-426.  
https://doi.org/10.1007/s11707-010-0125-2

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Sediment transport directions in four point bars of an ephemeral meandering river Usri, India, were measured from sedimentary structures and compared with the flow directions of the adjacent river-channel flow. As the bars were crescentic in shape, each bar has been divided into several sectors along with the adjacent river-channel bend. Vector means of sediment transport directions in each sector were computed and compared with the vector means of the flow directions of the corresponding river-channel sector. The relationship between the sediment transport direction in the bar and the water flow direction of the adjacent river-channel is sometimes divergent and sometimes convergent. However, the difference between the vector means of the sediment transport direction in the bar and the flow direction of the adjacent river-channel water is subtle. Hence, it can be concluded that the sediment transport direction in the bar is parallel to the flow direction of the adjacent river-channel water. Therefore, the result of the present study implies reconstructing the paleo-river channel course.

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Resource degradation and livelihood in the coastal region of Bangladesh
Giashuddin MIAH, Nasimul BARI, Abiar RAHMAN
Front Earth Sci Chin. 2010, 4 (4): 427-437.  
https://doi.org/10.1007/s11707-010-0126-1

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A study was conducted in four selected upazilas under four coastal districts through participatory rural appraisal (PRA), household survey and monitoring, sampling, focal group discussions, personal interview, on-farm field visits, institutional consultations, and secondary information. The investigation revealed that the valuable natural resources of the whole region are at the verge of serious degradation. Various causes have been identified, which are responsible for degradation of both resources and production environments. These causes include human population growth, coastal embankment, upstream withdrawal of Ganges water, brackish water shrimp farming, salt production, use of agro-chemicals, industrial activities, commercial activities, over-exploitation, etc. The study also showed that the degradation of natural resources is the reason behind the squeezing of historically dominant livelihood opportunities of the coastal communities. The current scenarios of the coastal ecosystem urge necessary steps to be taken for sustainable management of valuable resources and to create alternative livelihood opportunities for the coastal communities.

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Threatened wetlands and ecologically sensitive ecosystems management in Bangladesh
Shafi Noor ISLAM
Front Earth Sci Chin. 2010, 4 (4): 438-448.  
https://doi.org/10.1007/s11707-010-0127-0

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Wetlands constitute a part of human heritage. It has played a significant role in the development of human culture and society. More over it contains very rich components of biodiversity of local, national, and regional significance. They also provide habitat for a variety of resident and migratory waterfowl, a significant number of endangered species, and a large number of commercially important species. Mangrove wetlands are unique environments of floral-faunal assemblages, providing a complex detritus-based food-web for a number of marine and brackish water organisms. Wetlands in Bangladesh have great importance for the country’s economic, industrial, ecological, socioeconomic, and cultural aspects. There are five types of wetlands available in Bangladesh, such as saltwater wetlands, freshwater wetlands, palustrine wetlands, lacustrine wetlands, and manmade wetlands. There are 43 designated wetlands, and some are under threat from indiscriminate utilization, encroachments and reclamation, urbanization and drawbacks from agricultural development, and flood control. Almost 50% of the country’s people are directly dependent on wetlands resources. The vast majority of the poor people in the wetlands areas are dependent on wetlands resources for their nourishment. Wetlands have potential and have been recognized as a driving force for biodiversity conservation and rural socioeconomic improvement. Smart-use of wetlands can solve the ecosystems problems in the floodplain areas. A comprehensive analysis of the various issues leading to wetlands degradation is made in this study. The country needs an adequate interdisciplinary policy and political will to implement it for sustainable management and protection of wetlands and ecologically sensitive ecosystems in Bangladesh. Therefore, a reliable data bank is provided in this study to enhance the conservation measures initiated by the Government.

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Clay minerals in the major Chinese coastal estuaries and their provenance implications
Chunyan MA, Jing CHEN, Yuanjun ZHOU, Zhanghua WANG
Front Earth Sci Chin. 2010, 4 (4): 449-456.  
https://doi.org/10.1007/s11707-010-0130-5

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A sea-survey was carried out along the Chinese coast from the Bohai Sea to South China Sea, and 15 surficial samples were taken from major coastal estuaries, i.e., from north to south, the Yellow, abandoned Yellow, Yangtze, Qiantang, Ou, Min, Han, and Pearl River estuaries. On the basis of clay mineral analysis and published data collection, this paper discusses the characteristics of clay minerals of each coastal river and potentials of implications of sediment sources. The results show that the change of diagnostic clay minerals from smectite to kaolinite from the Yellow to the Pearl River estuaries is southward, as clearly shown by the ratios of smectite to chlorite (S/Ch) and kaolinite to illite (K/I). S/Ch decreases southward, while K/I moves reversely, implying change in climate setting from cool/dry to humid/hot with intensified weathering processes. Besides, these two indicators in the estuaries are also linked with the derivation of parent-rock of each river-basin and coastal hydrodynamics. The disproportional higher ratio of K/I in the Yellow and abandoned Yellow River estuaries is ascribed to their sediment sources with abundant loess component in the north-central China. The K/I decrease offshore from the Pearl River estuary is primarily due to hydrodynamic sorting. Therefore, the S/Ch and K/I of the present study comprehensively reflect the controls of climate, parent-rock, and sediment transport along the coast.

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Quantitative descriptors for identifying plant species of urban landscape vegetation
Jianhua ZHOU, Yifan ZHOU
Front Earth Sci Chin. 2010, 4 (4): 457-462.  
https://doi.org/10.1007/s11707-010-0128-z

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This paper discusses the ideas and methods of designing effective descriptors for identifying plant species of urban landscape vegetation. Fourteen of such descriptors induced from image spectrum, texture, and shape properties were designed. These descriptors were intended to meet such requirements as possessing a true physical or geometric implication relating to ecological significance, having a relatively steady segmentation threshold and being less sensitive to image types or environmental conditions during image acquisition. This study used decision trees to combine four selected descriptors for plant species identification, and the experiment was able to reach an error rate of 5.8% compared 25.9% by merely using the conventional pixel brightness values in plant species identification.

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Impacts of hydrological conditions on enzyme activities and phenolic concentrations in peatland soil: An experimental simulation
Xingting SUN, Wu XIANG, Ling HE, Yulong ZHAO
Front Earth Sci Chin. 2010, 4 (4): 463-470.  
https://doi.org/10.1007/s11707-010-0140-3

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Impacts of hydrological conditions on peatland soil enzyme activities and phenolic concentrations were investigated using peat cores from two typical peatlands, the forest swamp and the marsh in North-east China, under water level manipulation in the laboratory. The results indicated varied impacts of dry and waterlogged conditions on soil enzyme activities, depending on the confounding factors including the peatland types and the variation frequency of hydrological conditions. Carbon-related enzyme activities, phenol oxidase and β-glucosidase, were much higher in the marsh than in the forest swamp. On the contrary, phenolic concentration was measured to be much higher in the latter. Soil enzyme activities and phenolic concentrations were found to vary between the two peatlands, much more remarkably than within the individual peatlands caused by the changes in the water level. The negative relationship or inconspicuous correlation between phenolics and phenol oxidase was found to vary with specific soil conditions. These results implied that the enzyme activities and phenolic concentrations might be related to the developmental stages or the types of wetlands more than to hydrological conditions.

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Influence of using rice husk ash in soil stabilization method with lime
A. J. CHOOBBASTI, H. GHODRAT, M. J. VAHDATIRAD, S. FIROUZIAN, A. BARARI, M. TORABI, A. BAGHERIAN
Front Earth Sci Chin. 2010, 4 (4): 471-480.  
https://doi.org/10.1007/s11707-010-0138-x

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In clayey lands, swelling problem causes vertical displacements on road subbase, and finally, failure in pavement occurs due to lack of appropriate drainage systems. One popular and inexpensive method of soil stabilization is using lime. Investigations indicate that based on environmental and atmospheric conditions, the chemical reaction of lime and clayey soil is not accomplished well, owning to low temperature and high humidity. This paper aims to investigate the influence of adding rice husk ash on the reaction between soil and lime and lime reaction and determine soil physical and mechanical characteristics. Therefore, sufficient laboratory soil tests, such as Atterberg limits, compaction, California bearing ratio (CBR), and direct shear test are carried out, and the results are analyzed. The results generally indicate that adding lime and rice husk ash (RHA) causes a decrease in dry density and an increase in optimum water content. Increasing lime and RHA causes a decreasing rate in soil liquid limit and plastic limit. Adding lime and RHA to the soil causes a decrease in deformability of soil samples and gives more brittle materials. Also, this action causes an increase in shear strength. Moreover, increasing in CBR amount under the influence of increasing RHA is one of the main results of this paper.

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12 articles