Surface recovery of landslides triggered by 2008 <Emphasis Type="Italic">Ms</Emphasis>8.0 Wenchuan earthquake (China): a case study in a typical mountainous watershed     

Lingjing Li  Xin Yao  Yongshuang Zhang  Javed Iqbal  Jian Chen  Nengjuan Zhou 《Landslides》2016,13(4):787-794

The Ms8.0 Wenchuan earthquake that occurred on 12 May 2008 in southwestern China and triggered numerous landslides is one of the stronger ones in the steep eastern margins of the Tibetan Plateau. The surfaces of these landslides have recovered gradually with vegetation, which provide useful information about the evolution of geologic environment as well as the long-term assessment of landslides after earthquake. The Mianyuanhe watershed shows many co-seismic landslides. The active fault passing through its center is selected as a study area aiming to analyze the annual surface recovery rate (SRR) of landslides by interpretation of remote-sensing images in five periods from 2008 to 2013. The results are here described. (1) Although a large amount of loose deposits were transformed into debris flows, the surfaces of the landslides recovered rapidly with vegetation and almost no landslides occurred at new sites after the Wenchuan earthquake. In the year 2008, the exposed surface projected area (ESPA) of the landslides showed a total area of 56.3 km² and covered 28.9 % of the study area, which was reduced rapidly to 19.1 % in 2011 and 15.8 % in 2013. (2) The study area was divided into four geologic units, including clastic rocks, melange zone, carbonate rocks, and magmatic rocks. Smaller ESPAs and higher SRRs were found in the former two units versus the latter ones. (3) A single large landslide shows an SRR lower than a group of smaller ones having an equal total surface, while the SRRs of debris flows are lower than those of rockfalls and landslides. (4) The vegetation cover would return to the pre-earthquake level in 2020 approximately, which indicates that the impact of the Wenchuan earthquake on landslides and debris-flows activities would cease almost completely.  相似文献   

Geomorphological study of Bulandshahr District (U.P.) using remotely sensed data     

Akram Javed 《Journal of the Indian Society of Remote Sensing》2000,28(2-3):115-127

Remote sensing data pertaining to LANDSAT TM FCC of bands 2, 3 and 4 of 9th May 1991 and IRS-1A LISS II digital data of 3rd May 1991, have been utilized for the study of geomorphology of Bulandshahr district, U.P. Visual interpretation technique has been followed for geomorphological mapping and the area has been separated into four broadly defined geomorphic zones, namely Varahasi Older Alluvial Plain, Aligarh Older Alluvial Plain, Terrace Zone and Recent Flood Plains of Ganga and Yamuna, each characterized by its own geomorphic/landform elements discernable on remote sensing data. The Varanasi Older Alluvial Plain represents the oldest geomorphic surface occurring at highest tectonic level in the Gangetic plain. The Aligarh Older Alluvial Plain represents a palaeo-flood plain of a north flowing palaeo-drainage in the area. The Terrace zone represents the older flood plain of Ganga and its tributaries. The Recent Flood Plains of Ganga and Yamuna rivers, which get periodically inundated, constitute the youngest geomorphic surface in the study area. Digital image processing outputs, particularly ratio images have been found to be helpful in identifying certain geomorphic landforms (old/abandoned channels, scars etc.) due to greater contrast within ratio images.  相似文献   

3D numerical simulation of flow field around twin piles     

Ata Amini  Akram Asadi Parto 《Acta Geophysica》2017,65(6):1243-1251

In this study to identify the flow pattern and local scour mechanism around pile groups, the flow field was simulated using FLOW-3D software. A pair of pile on a flat-bed channel with side by side and tandem arrangements was investigated. To establish Navier–Stokes equations, the RNGk-ε turbulence model was used and the results were verified using experimental data. In case of FLOW-3D capability, it was found that the software was able to properly simulate the expected interaction between the pile groups. The results of flow field simulation showed that Reynolds number and the pile spacing are the most influential variables in forming vortices. The flow around tandem pile and the downward flow around wake vortices were more intense and complicate in comparison with side by side arrangements and single pile.  相似文献   

Modelling flow and sediment trapping upstream and within grass buffer strips          下载免费PDF全文

Sina Akram  Bofu Yu  Hossein Ghadiri 《水文研究》2015,29(14):3179-3192

Grass buffer strips impact the hydrology of flow and consequently the fate of sediment. A complex process‐based model is developed to predict flow characteristics as well as sediment deposition and transport upstream, and within grass strips. The model is capable of estimating the proportion and amount of different sediment particle size classes in the outflow. The modified Green–Ampt equation was used to simulate infiltration. Gradually varied flow and kinematic wave approximation were used to model flow characteristics upstream and within grass strips. The GUEST model approach has been modified in order to use its basic approaches in sediment transport module in grass strips. Model predictions agree well with the results of two sets of controlled experiments. The bias, coefficient of model efficiency and the root mean squared error of the modelled efficiency of grass strips in reducing sediment concentration were 0.93–0.99, 0.58–0.99 and 8.9–12.7, respectively. The sensitivity analysis showed that the initial soil moisture and flow rate are the most sensitive parameters in predicting runoff loss. Increasing the slope steepness and flow rate dramatically decreases the efficiency of grass strips in reducing sediment concentration and mass. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Watershed prioritization using morphometric and land use/land cover parameters: A remote sensing and GIS based approach   总被引：4，自引：0，他引：4  

Akram Javed  Mohd Yousuf Khanday  Subah Rais 《Journal of the Geological Society of India》2011,78(1):63-75

Jaggar watershed is a constituent of the Gambhir river basin, in eastern Rajasthan and covers an area of 352.82 km², representing arid climate. The drainage network is dendritic to sub-dendritic pattern however parallel to sub-parallel has also developed locally. The Jaggar watershed has been divided into fourteen sub-watersheds, designated as SW1 to SW14, for prioritization purpose. The prioritization of the sub-watersheds has been done on the basis of morphometric analysis and land use/land cover categories. Various morphometric parameters (linear and shape) have been determined for each sub-watershed and assigned rank on the basis of value/relationship with erodibility so as to arrive at a compound value for final ranking of the sub-watersheds. Land use/land cover mapping has been carried out using IRS LISS III data of 1998. Based on morphometric and land use/land cover analysis and their ranks, the subwatersheds have been classified into four categories as very high, high, medium and low in terms of priority for conservation and management of natural resources. The prioritization results based on morphometry reveal that only SW7 and SW10 fall under very high priority, whereas SW6, SW11 and SW13 fall under very high priority on the basis of land use/land cover analysis. However on the integration of morphometry and land use/land cover only SW14 show common priority whereas rest have little or no correlation.  相似文献   

Comparison of rockfall susceptibility assessment at local and regional scale: a case study in the north of Beijing (China)     

Xueliang Wang  Luqing Zhang  Jixin Ding  Qingfeng Meng  Javed Iqbal  Lihui Li  Zhifa Yang 《Environmental Earth Sciences》2014,72(11):4639-4652

This study shows a rockfall susceptibility assessment at local scale in north Beijing of China, including the identification of rockfall sources onsite by terrain and rock discontinuities analysis and run-out distance prediction by Rocfall^? simulation. Two types of rockfall were defined including one type on the cliffs with long inclined slopes and another type on the road slopes with low height. Two historical rockfall events were used to back-calibrating the parameters used for run-out distance simulation. Based on the work, rockfall susceptibility map at local scale was created in GIS, which was compared with the map obtained at regional scale (entire Huairou district scale). Due to the difference of approaches applied, procedure of assessment and types of source data acquired, the two resulting rockfall susceptibility maps are proved to be different. Still, both of them are useful and could be used at different level’s decision for rockfall prevention and mitigation. Different types of uncertainties exist in the study of rockfall susceptibility assessment. To reduce the uncertainties, studies on both approaches and techniques are suggested.  相似文献   

Satellite-based analysis of the role of land use/land cover and vegetation density on surface temperature regime of Delhi,India     

Yogesh Kant  B. D. Bharath  Javed Mallick  Clement Atzberger  Norman Kerle 《Journal of the Indian Society of Remote Sensing》2009,37(2):201-214

The knowledge of the surface temperature is important to a range of issues and themes in earth sciences central to urban climatology, global environmental change and human-environment interactions. The study analyses land surface temperature (LST) estimation using temporal ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) datasets (day time and night time) over National Capital Territory Delhi using the surface emissivity information at pixel level. The spatial variations of LST over different land use/land cover (LU/LC) at day time and night time were analysed and relationship between the spatial distribution of LU/LC and vegetation density with LST was developed. Minimum noise fraction (MNF) was used for LU/LC classification which gave better accuracy than classification with original bands. The satellite derived emissivity values were found to be in good agreement with literature and field measured values. It was observed that fallow land, waste land/bare soil, commercial/industrial and high dense built-up area have high surface temperature values during day time, compared to those over water bodies, agricultural cropland, and dense vegetation. During night time high surface temperature values are found over high dense built-up, water bodies, commercial/industrial and low dense built-up than over fallow land, dense vegetation and agricultural cropland. It was found that there is a strong negative correlation between surface temperature and NDVI over dense vegetation, sparse vegetation and low dense built-up area while with fraction vegetation cover, it indicates a moderate negative correlation. The results suggest that the methodology is feasible to estimate NDVI, surface emissivity and surface temperature with reasonable accuracy over heterogeneous urban area. The analysis also indicates that the relationship between the spatial distribution of LU/LC and vegetation density is closely related to the development of urban heat islands (UHI).  相似文献   

Application of Analytic Signal and Euler Deconvolution in Archaeo-Magnetic Prospection for Buried Ruins at the Ancient City of Pelusium, NW Sinai, Egypt: A Case Study   总被引：1，自引：0，他引：1  

Akram Mekhael Aziz  William August Sauck  El-Arabi Hendi Shendi  Mohamed Ahmed Rashed  Mohamed Abd El-Maksoud 《Surveys in Geophysics》2013,34(4):395-411

Progress in the past three decades in geophysical data processing and interpretation techniques was particularly focused in the field of aero-geophysics. The present study is to demonstrate the application of some of these techniques, including Analytic Signal, Located Euler Deconvolution, Standard Euler Deconvolution, and 2D inverse modelling, to help in enhancing and interpreting the archeo-magnetic measurements. A high-resolution total magnetic field survey was conducted at the ancient city of Pelusium (name derived from the ancient Pelusiac branch of the Nile, and recently called Tell el-Farama), located in the northwestern corner of the Sinai Peninsula. The historical city had served as a harbour throughout the Egyptian history. Different ruins at the site have been dated back to late Pharaonic, Graeco-Roman, Byzantine, Coptic, and Islamic periods. An area of 10,000 m², to the west of the famous huge red brick citadel of Pelusium, was surveyed using the magnetic method. The chosen location was recommended by the Egyptian archaeologists, where they suspected the presence of buried foundations of a temple to the gods Zeus and Kasios. The interpretation of the results revealed interesting shallow-buried features, which may represent the Temple’s outer walls. These walls are elongated in the same azimuth as the northern wall of the citadel, which supports the hypothesis of a controlling feature such as a former seacoast or shore of a distributary channel.  相似文献   

Physical and numerical investigation of a cemented granular assembly of steel spheres     

M. S. Akram  G. B. Sharrock 《国际地质力学数值与分析法杂志》2010,34(18):1896-1934

In this paper, steel spheres embedded in a cement matrix were studied using numerical and physical ISRM testing procedures. A challenge in discrete element simulations is to select appropriate micro‐mechanical models and parameters, to recover the observed macro‐mechanical behavior. An ideal experiment on cohesive granular assemblies constructed identical to numerical ones would validate these micro models for a set of measured micro‐parameters. The first part of the paper summarizes the previous studies in this area, outlines such experimental methodology and depicts the steps followed for the preparation and the testing of cemented granular assemblies together with the derivation of micro‐parameters. The second part discusses the results of numerical and physical ISRM standard tests including uniaxial and triaxial compression, Brazilian tensile and shear box tests. Physical samples were prepared using steel balls bonded with Portland cement, cured under controlled laboratory conditions and tested in compression, tension and shearing. Acoustic emissions were monitored in uniaxial tests to characterize the damage thresholds relative to volumetric strains. Numerical simulations were conducted with PFC 3D using micro‐mechanical parameters derived from physical testing. Parametric sensitivity studies were carried out to look into the dependency of macroscopic responses on the parameters. The results from both numerical and physical tests showed good correspondence in macroscopic behavior i.e. peak strength, stages of damage, mode of failures. However, the numerical simulations reflected a stiffer mechanical response than physical assemblies. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Augmentation of seasonal low stream flows by artificial recharge in the Spokane Valley-Rathdrum Prairie aquifer of Idaho and Washington, USA     

Michael E. Barber  Akram Hossain  John J. Covert  Guy J. Gregory 《Hydrogeology Journal》2009,17(6):1459-1470

Conjunctive management of surface water and groundwater requires sophisticated spatial and temporal analysis. In situations involving multiple jurisdictions such as state boundaries, management problems are magnified due to often conflicting regulations and policies. A transient MODFLOW model of the Spokane Valley-Rathdrum Prairie (SVRP) aquifer/river system mutually accepted by both the states of Idaho and Washington, USA, was used to evaluate regional solutions to potential water shortages through the use of strategically placed infiltration basins or injection wells. Artificial recharge of the SVRP aquifer was simulated using diversions from Lake Pend Oreille during winter periods when flows are high and excess water is available. Alternative locations for potential wells and detention basins were examined. Lag times for the water to impact stream/groundwater interaction areas along the Spokane River were evaluated to assess the potential for augmenting stream flows from July through September. Results indicated that the aquifer could be used to improve low-flow season streamflow values utilizing both infiltration basins and injection wells with winter surface water diversions. Depending on the location, as much as 30% of the winter diversion rate could be lagged to improve summer flows at the Spokane gage. Thus, a regional mitigation strategy is scientifically feasible.  相似文献