Relationship between bedload and suspended sediment in the sand-bed Exu River,in the semi-arid region of Brazil     

Jose Ramon B. Cantalice  Moacyr Cunha Filho  Borko D. Stosic  Victor Casimiro Piscoya  Sergio M. S. Guerra  Vijay P. Singh 《水文科学杂志》2013,58(8):1789-1802

Abstract

Suspended sediment and bedload discharges in sand-bed rivers shape semi-arid landscapes and impact sediment delivery from these landscapes, but are still incompletely understood. Suspended sediment and bedload fluxes of the intermittent Exu River, Brazil, were sampled by direct measurements. The highest suspended sediment concentration observed was 4847.4 mg L^-1 and this value was possibly associated with the entrainment of sediment that was deposited in the preceding year. The bedload flux was well related to the stream power and the river efficiently transported all available bedload with a mean rate of 0.0047 kg m^-1 s^-1, and the percentage of bedload to suspended sediment varied between 4 and 12.72. The bed sediment of Exu River was prone to entrainment and showed a proclivity for transport. Thus, sand-bed and gravel-bed rivers of arid environments seem to exhibit the same mobility in the absence of armour layer.

Editor D. Koutsoyiannis; Associate editor B. Touaibia

Citation Cantalice, J.R.B., Cunha Filho, M., Stosic, B.D., Piscoya, V.C., Guerra, S.M.S., and Singh, V.P., 2013. Relationship between bedload and suspended sediment in the sand-bed Exu River, in the semi-arid region of Brazil. Hydrological Sciences Journal, 58 (8), 1789–1802.  相似文献   

Strength characteristics of compacted pond ash     

S.P. Singh  A. Sharan 《Geomechanics and Geoengineering》2014,9(1):9-17

Strength properties of compacted ash layers depend to a great extent on the moulding conditions. This paper focuses on the effects of compaction energy and degree of saturation on strength characteristics of compacted pond ash. The pond ash sample, collected from the ash pond of Rourkela Steel Plant (RSP), was subjected to compactive energies varying from 357 kJ/m³ to 3488 kJ/m³. The optimum moisture content and maximum dry densities corresponding to different compactive energies were determined by conventional compaction tests. The shear strength parameters, unconfined compressive strengths (UCS) and California bearing ratio (CBR) values of specimens compacted to different dry densities and moisture content were assessed and reported. The effects of compaction energy and degree of saturation on shear strength parameters i.e. unit cohesion (c_u) and angle of internal friction (Ф) values and also the UCS values are evaluated and presented herein. The results indicate that the dry density and strength of the compacted pond ash can be suitably modified by controlling the compactive energy and moulding moisture content. The strength achieved in the present study is comparable to the good quality, similar graded conventional earth materials. Hence, it may be safely concluded that pond ash can replace the natural earth materials in geotechnical constructions.  相似文献   

Biodegradation of benzo(a)pyrene mediated by catabolic enzymes of bacteria     

S. Mishra  S. N. Singh 《International Journal of Environmental Science and Technology》2014,11(6):1571-1580

An investigation was carried out to compare the ability of two bacteria Pseudomonas aeruginosa PSA5 and Rhodococcus sp. NJ2 isolated from petroleum sludge for degradation of benzo(a)pyrene [B(a)P], a HMW PAH compound in MSM. During 25 days of incubation, 50 ppm B(a)P was degraded by 88 and 47 % by P. aeruginosa PSA5 and Rhodococcus sp. NJ2, respectively. Besides, involvement of different catabolic enzymes, that is, salicylate hydroxylase, 2-carboxybenzaldehyde dehydrogenase, catechol 1,2-dioxygenase and catechol 2,3-dioxygenase, was also examined to identify their differential role in B(a)P degradation. Among these enzymes, the highest induction of 2-carboxybenzaldehyde dehydrogenase (773.5 nmol mg^?1 protein) was recorded in P. aeruginosa PSA5, while salicylate hydroxylase was highly expressed (839.6 nmol mg^?1 protein) in Rhodococcus sp. NJ2. Both the bacteria were found biosurfactant (glycolipid) producing, and role of biosurfactant in PAH degradation was also ascertained by reduced surface tension, higher emulsification index and increased cell surface hydrophobicity.  相似文献   

Aquifer system response to intensive pumping in urban areas of the Gangetic plains,India: the case study of Patna     

Dipankar Saha  S. N. Dwivedi  Raj K. Singh 《Environmental Earth Sciences》2014,71(4):1721-1735

A significant component of domestic demand for water of urban areas located in the Gangetic plains is met by heavy pumping of groundwater. The present study is focused on the Patna municipal area, inhabited by 17 million people and spanning over 134 km², where entire urban water demand is catered from pumping by wells of various capacities and designs. The present study examines the nature of the aquifer system within the urban area, the temporal changes in the water/piezometric level and the recharge mechanism of the deeper aquifers. The aquifer system is made up of medium-to-coarse unconsolidated sand, lying under a ~40-m-thick predominantly argillaceous unit holding 8- to 13-m-thick localised sand layers and continues up to 220 m below ground. Groundwater occurs under semi-confined condition, with transmissivity of aquifers in 5,500–9,200 m² day^?1 range. Hydraulic head of the deeper aquifer remains in 9–19 m range below ground, in contrast to 1–9 m range of that of the upper aquitard zone. The estimated annual groundwater extraction from the deeper aquifer is ~212.0 million m³, which has created a decline of 3.9 m in the piezometric level of the deeper aquifer during the past 30 years. Unregulated construction of deep tube wells with mushrooming of apartment culture may further exacerbate the problem. The sand layers within the aquitard zone are experiencing an annual extraction of 14.5 million m³ and have exhibited stable water level trend for past one and half decades. This unit is recharged from monsoon rainfall, besides contribution from water supply pipe line leakage and seepage from unlined storm water drains.  相似文献   

Assessment of groundwater quality with special reference to arsenic in Nawalparasi district,Nepal using multivariate statistical techniques     

Ishwar Chandra Yadav  Ningombam Linthoingambi Devi  Devendra Mohan  Qi Shihua  Surendra Singh 《Environmental Earth Sciences》2014,72(1):259-273

Groundwater is a precious resource for humankind not only in Nepal but also across the globe due to its diverse functions. A total of 48 groundwater samples were collected from three villages of Nawalparasi district, Nepal, during pre-monsoon and monsoon to estimate the overall groundwater quality and to identify the sources of contamination with emphasis on arsenic (As). The average concentrations of all tested groundwater quality parameters (temp., pH, EC, ORP, Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl^?, F^?,SO₄ ^2?, PO₄ ^3?, HCO₃ ^?, NO₃ ^?, Cu, Ni, Mn, Cd, Pb, Fe, Zn, Cr, and As) were well within permissible limits of WHO for drinking water, except for Ni, Cd, Pb, Cr, and As. Concentration of As ranged from 60 to 3,100 μg L^?1 and 155 to 1,338 μg L^?1 in pre-monsoon and monsoon, respectively. The Piper diagram of the groundwater chemistry showed groundwater of Nawalparasi belongs to Ca–Mg–HCO₃ and Mg–HCO₃ water type with HCO₃ ^? as dominant ions. As content in the study area was negatively correlated with Fe in pre-monsoon, while it was positively correlated in monsoon. Furthermore, As was negatively correlated with oxidation reduction potential suggesting reducing condition of groundwater. Principal component analysis revealed seven major factors that explained 81.996 and 83.763 % of total variance in water quality in pre-monsoon and monsoon, respectively. The variance of water quality was related mainly with the degree of water–rock interaction, mineralization, and anthropogenic inputs.  相似文献   

GIS-based morpho-tectonic studies of Alaknanda river basin: a precursor for hazard zonation     

D. P. Shukla  C. S. Dubey  A. S. Ningreichon  R. P. Singh  B. K. Mishra  S. K. Singh 《Natural Hazards》2014,71(3):1433-1452

Alaknanda river basin is considered to be tectonically active where damaging earthquakes and landslides have occurred. The whole basin was divided into 8 sub-basins to carry out morphometric analyses, hypsometric integral (HI) analysis and valley floor width to valley height ratio (V _f) factor. The sub-basins 2 and 3 show that they are highly active, because of the higher values of bifurcation ratio, stream frequency asymmetric factor, and lower values of form factor, elongation ratio and circulatory ratio. In these areas, HI values are very low indicating that the landscape is highly eroded, deeply dissected and tectonically active. The result obtained from V _f was similar which classified both these basins as highly active. Morphometric analysis, HI and V _f analyses along with structural map of study area are used to prepare morpho-tectonic map classifying the whole area into very high, high, moderate and low zones of tectonic activity. This map clearly indicates that the areas near MCT II (Munsiari Thrust), MCT III (Ramgarh Thrust) and North Almora Thrust are tectonically very active which fall in sub-basins 2, 3, 4 and parts of 5. Various locations such as Chamoli, Birahi, Pipalkoti, Rudraprayag, etc. are situated in these zones where many earthquakes and landslides occur every year. Moreover, the data plotted for earthquakes and landslides occurrences are consistent with morpho-tectonic map and can be used as a precursor for demarcation of natural hazard vulnerable zones.  相似文献   

Earthquake damage identification: a case study using soft classification approach     

Sandeep Singh Sengar  Sanjay Kumar Ghosh  Anil Kumar  Hans Raj Wason 《Natural Hazards》2014,71(3):1307-1322

The October 8, 2005, Kashmir earthquake (M _w 7.6) affected the rough mountainous regions of India and Pakistan with poor accessibility, and thus, no proper comprehensive ground survey was possible. However, due to the ability of remote sensing technology to acquire spectral measurements of damaged areas at various spatial and temporal scales, extraction of damaged areas can be carried out quickly and with great reliability. The fuzzy-based classifiers [Possibilistic c-Means (PCM), noise cluster (NC), and NC with entropy (NCE)] were applied to identify 2005 Kashmir earthquake, induced landslides, as well as built-up damage (BD) areas, as soft computing approaches using supervised classification. Results indicate that for the identification of landslides and BD areas, NCE classifier generated the best outputs, while for the identification of built-up undamaged areas, NC classifier generated the best output. Further, it was found that the proposed Class Based Sensor Independent (CBSI) technique can improve spectral information of specific class for better identification.  相似文献   

Temporal variation of soil radon and thoron concentrations in Mizoram (India), associated with earthquakes     

H. P. Jaishi  S. Singh  R. P. Tiwari  R. C. Tiwari 《Natural Hazards》2014,72(2):443-454

Continuous soil-gas radon and thoron measurements were carried out at 15 days interval along Mat fault in Mizoram (India), which lies in the seismic zone V of the seismic zonation map of India. The study was carried out from March 2012 to February 2013 using LR-115 Type II detectors, manufactured by Kodak Pathe, France. The effect of meteorological parameters on radon and thoron data was taken into consideration. The annual average value of radon and thoron concentration was found to be 621.21 and 590.18 Bq/m³ with a standard deviation of 377.60 and 301.34 Bq/m³, respectively. Inverse correlation coefficient was obtained between radon/thoron concentration and the meteorological parameters except in one case (thoron and relative humidity) which showed a weak positive correlation. Standard deviation method was employed in order to differentiate those anomalies which are solely caused by seismic events and not by meteorological parameters. The data obtained have been correlated with the seismic activities that occurred around the measuring site. Positive correlations were found between radon/thoron data and the earthquakes.  相似文献   

Impact of the 2004 Indian Ocean tsunami along the Tamil Nadu coastline: field survey review and numerical simulations     

G. Gopinath  F. Løvholt  G. Kaiser  C. B. Harbitz  K. Srinivasa Raju  M. Ramalingam  Bhoop Singh 《Natural Hazards》2014,72(2):743-769

The 2004 Indian Ocean tsunami had a significant impact on the Tamil Nadu coast in India. In this paper, a range of field survey data collected by different survey teams available in literature have been analyzed and compiled to serve as a basis for validation of numerical tsunami simulations. The individual field surveys reveal a significant scatter in the run-up data between the different teams, which point out that the uncertainty in these data must be taken into account when using them for validation. The inundation of the 2004 Indian Ocean tsunami is simulated for the coastlines of Chennai and Nagapattinam based on high-resolution topography. Different spatially uniform Manning friction as well as heterogeneous friction maps is used. Overall, the simulation results showed a good agreement with the field observations, but there are also some observed spatial variability in the goodness of the fit between the data and simulations. In some areas, clear discrepancies are found. The results obtained using detailed land use maps including spatially variable friction are not significantly more accurate than those employing spatially constant values. For most areas, parameters indicating relatively low friction provided best match with the observations. This may also suggest that the inundation is often strongly governed by local variations in topography.  相似文献   

Cyclic Thermo-Mechanical Analysis of Wellbore in Underground Compressed Air Energy Storage Cavern     

S. Mohanto  K. Singh  T. Chakraborty  D. Basu 《Geotechnical and Geological Engineering》2014,32(3):601-616

The compressed air energy storage (CAES) method is a viable method of storing surplus energy underground when there is a mismatch between energy generation and demand. Wellbores embedded in rock are an integral part of energy storage structures, and are used for injecting and extracting the compressed air. During injection and production cycles, the storage reservoir and wellbore are subjected to cyclic change in external pressure and temperature, which may cause failure of the wellbore. In this paper, cyclic thermo-mechanical analysis of a horizontal wellbore in an underground CAES cavern is performed using finite element analysis. The rock behavior is simulated using the Mohr-Coulomb constitutive law. The reduction in the yield strength of rock with increase in the number of loading cycles is taken into account in the analysis. Parametric sensitivity studies are carried out to study the effects of dilation and friction angles of rock, the ratio of in situ horizontal and vertical stresses, loading frequency, and the magnitude of the temperature cycles in the cavern on the wellbore performance for different types of rock. The thermo-mechanical cyclic behavior leads to plastic strains that are greater than those obtained by performing mechanical analysis only. Significantly large deformation is generated in rock for large dilation angle and high loading frequencies.  相似文献