Cyclones and storm surges in Bangladesh: Some mitigative measures

Bangladesh, with its repeated cycle of floods, cyclones, and storm surges, has proved to be one of the most disaster-prone areas of the world. During the years from 1797 to 1991, Bangladesh has been hit by 60 severe cyclones (mostly accompanied by storm surges). This paper gives a brief account of these disasters with particular reference to the wind speed, surge height, loss of life, and damage to crops and properties, etc.In order to protect the coastal areas of Bangladesh from cyclonic storm surges and floods, a major system of embankments was constructed during the 1960s and 1970s, but this is now in need of rehabilitation. The Cyclone Protection Project, which was approved by the World Bank in 1989, would rehabilitate some of the existing embankments, build new embankments, and construct roads. Locally available materials, indigenous technology, and cheap surplus manpower should be used in this project. A variety of fruit trees should be planted along the dikes and roads.To the south-western part of Bangladesh bordering the Bay of Bengal, lies the world's largest single mangrove tract, known as the Sunderban, which covers a total area of 571 500 ha. This mangrove forest is of extreme importance since it provides efficient protection to life and property against cyclones and storm surges. But due to deforestation, the width of the mangrove belt is being rapidly diminished. The author therefore lays emphasis on coastal afforestation.Absolute security against cyclone hazard is probably out of the question, but an effective cyclone warning response can definitely reduce loss of life and damage to property. The author discusses the current conditions for cyclone forecasting and warning in Bangladesh, and then puts forward some proposals for improving the Cyclone Preparedness Programme.     

The Jinadriyah anticlines: a surface model for oil fields in eastern Saudi Arabia

Mesozoic oil in Saudi Arabia exists in north/south-oriented anticlines. Such anticlines are usually studied using subsurface data. The present study introduces, for the first time in Saudi Arabia, a surface analog for these anticlines. The study covers two northerly oriented anticlines located in the Jinadriyah area at 15 km to the northeast of the Riyadh city. They are named herein the North and South Jinadriyah anticlines. The outcrops in both anticlines belong to the Lower Cretaceous Yamama Formation which consists of limestone in its lower part and limestone with shale in its upper part. The study included initially detailed interpretation of Google Earth and Landsat TM images to map the structural pattern of the anticlines. Detailed field mapping confirmed the satellite image interpretation and helped describe the geometry of the two anticlines in detail. The 3.5-km-long South Jinadriyah anticline is an open doubly plunging asymmetric anticline. The western flank is dissected by 13 minor reverse faults of north–south orientation. The North Jinadriyah anticline is about 5.5 km long and is relatively more complex than the South Jinadriyah anticline. It consists of northern, central, and southern segments that differ from each others in orientation and style. The anticline is dissected by 18 minor faults of different orientations and sense of displacement. Two perpendicular fracture sets with one being parallel to the anticline axes were recorded in the two anticlines. Both anticlines are interpreted as fault-propagation folds that were formed during the Late Cretaceous first Alpine orogeny. The mid-Late Tertiary second Alpine orogeny and Late Tertiary eastward tilting of the Arabian Plate increased the degree of folding and faulting.     

Detection of Magnetically Susceptible Dyke Swarms in a Fresh Coastal Aquifer

Groundwater constitutes the main source of freshwater in Shalatein, on the western coast of the Red Sea, in Egypt. The fresh aquifer of Shalatein is intensively dissected by shallow and deep faults associated with the occurrence of dykes and/or dyke swarms. In this context, synthesis of electrical resistivity, ground magnetics, and borehole data was implemented to investigate the freshwater aquifer condition, locate the intrusive dykes and/or dyke swarms, and demarcate the potential freshwater zones. Nine Schlumberger VES’s with maximum current electrode half-spacing (AB/2) of 682 m were conducted. The subsurface was successfully delineated by general four layers. The fresh aquifer of the Quaternary and Pre-Quaternary alluvium sediments was effectively demarcated with true resistivities ranged from 30 to 105 Ωm and thickness ranged between 20 and 60 m. A ground magnetic survey comprised 35 magnetic profiles, each 7 km in length. Magnetic data interpretation of the vertical derivatives (first and second order), downward continuation (100 m), apparent susceptibility (depth of 100 m), and wavelength filters (Butterworth high-pass of wavelengths <100 m and Band-Pass of wavelengths 30–100 m) successfully distinguished the near surface structure with five major clusters of dyke swarms, whereas filters of the upward continuation (300 m) and Butterworth low-pass (wavelengths >300 m) clearly reflected the deep-seated structure. The computed depth by the 3D Euler deconvolution for geological contacts and faults (SI = 0) ranged from 14 to 545 m, whereas for dyke and sill (SI = 1), it ranged from 10 to 1,095 m. The western part of the study area is recommended as a potential freshwater zone as it is characterized by depths >100 m to the top of the dykes, higher thickness of the fresh aquifer (45–60 m), depths to the top of the fresh aquifer ranging from 25 to 40 m, and higher resistivities reflecting better freshwater quality (70–105 Ωm).     

Supra-subduction affinity in the Neoproterozoic serpentinites in the Eastern Desert, Egypt: Evidence from mineral composition

Serpentinites in the Eastern Desert (ED) of Egypt represent integral components of the ophiolites. Metamorphic textures of the serpentinites preserve the complex mineralogical evolution from primary peridotite through metamorphism, and late-stage hydrothermal alteration. Two textural types are distinguished in the olivines of the present serpentinized peridotites, namely (a) highly-strained olivine grains with kink bands, as in the deformed mantle tectonites from ophiolites, and (b) non-strained grains. The latter may represent recrystallized crystals during later thermal metamorphic events due to the intrusion of granite. On the basis of X-ray diffraction analysis, antigorite is the main serpentine minerals with lesser chrysotile and lizardite which indicates that serpentinites were formed under prograde metamorphism. Relict primary minerals of the serpentinites are Cr-spinel, olivine and pyroxene. Chrome spinel relicts have high Cr# (0.60–0.80), whereas primary olivines are Mg-rich nature (Fo = 89–96). Geochemical compositions of serpentinites indicate that they formed not at mid-ocean ridges but at spreading centers associated with subduction zones and this could have happened in a supra-subduction zone either in the fore-arc or back-arc environments. Mineral compositions of primary chrome spinels and olivines are similar to those of modern fore-arcs. High Cr# in the relict chrome spinels and Fo in the primary olivines of serpentinites indicate that they are residual after extensive partial melting and originated by sea-floor spreading during subduction initiation.     

Geochemistry and environmental impacts of retorted oil shale from Jordan

Physical and chemical characterization of spent oil shale (OS) from El-Lajjun area has been carried out and compared with the original OS. The spent shale (SS) is subjected to leaching tests to detect the possibilities of heavy metals released from it into the environment. Standard column leaching experiments have revealed no detectable release of heavy metals to the percolating water. The effectiveness of the SS in removing Pb²⁺ from wastewater has been investigated. The SS is very efficient in removing most of Pb²⁺ where 1 m³ of SS has an efficiency to remove from 64 to 94% of Pb²⁺ from about 1,300 m³ wastewater sample containing 50 ppm Pb²⁺. The efficiency decreases substantially with increasing Pb²⁺ concentration in the wastewater. In real situations, where Pb²⁺ concentration is very low (i.e., less than 5 ppm), the efficiency of the SS is expected to be 100%.     

Die elektrochemische Bestimmung des im Wasser gelösten Sauerstoffs mit Hilfe einer modifizierten Membranelektrodentechnik

Zusammenfassung Die Anwendungsm?glichkeiten der elektrochemischen Sauerstoffbestimmung wurden durch die Einführung der Kurzzeitmessung erweitert. Diese Methode gibt eine gr?ssere Empfindlichkeit und erlaubt somit die Sauerstoffbestimmung im μg/l-Bereich. Ferner wurde ein System entwickelt, das von der Membrandicke und dem Membranmaterial unabh?ngig ist. Das ist ein Vorteil, der speziell für Sauerstoffmessungen in Kl?ranlagen interessant sein dürfte.

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Summary This paper presents a new electrochemical technique for DO measurements by means of membrane electrodes. In stead of the well-known steady state measurements, a transient technique which is more sensitive was used. This gives the possibility of measuring oxygen in the μl/l range. The system is independent of the membrane material and the membrane thickness. The stirring influence is considerably less than for steady state measurements. The independence of the membrane material will be especially useful for oxygen measurements in waste purification plants.

     

Quantifying changes in groundwater level and chemistry in Shahrood,northeastern Iran

Temporal changes in the quantity and chemical status of groundwater resources must be accurately quantified to aid sustainable management of aquifers. Monitoring data show that the groundwater level in Shahrood alluvial aquifer, northeastern Iran, continuously declined from 1993 to 2009, falling 11.4 m in 16 years. This constitutes a loss of 216 million m³ from the aquifer’s stored groundwater reserve. Overexploitation and reduction in rainfall intensified the declining trend. In contrast, the reduced abstraction rate, the result of reduced borehole productivity (related to the reduction in saturated-zone thickness over time), slowed down the declining trend. Groundwater salinity varied substantially showing a minor rising trend. For the same 16-year period, increases were recorded in the order of 24% for electrical conductivity, 12.4% for major ions, and 9.9% for pH. This research shows that the groundwater-level declining trend was not interrupted by fluctuation in rainfall and it does not necessarily lead to water-quality deterioration. Water-level drop is greater near the aquifer’s recharging boundary, while greater rates of salinity rise occur around the end of groundwater flow lines. Also, fresher groundwater experiences a greater rate of salinity increase. These findings are of significance for predicting the groundwater level and salinity of exhausted aquifers.     

<Emphasis Type="Italic">Salpingoporella</Emphasis> (dasycladalean algae) species from the Lower Cretaceous carbonate facies of Kopet Dagh basin (NE Iran)

Salpingoporella species from algal bearing of Barremian-Aptian limestones in the Kopet Dagh basin (NE of Iran) are described. Different species (S. cemi, S. hasi, S. heraldica, S. hispanica, S. milovanovici, S. muehlmbergi, S. parapiriniae, S. piriniae, S. cf. biokovensis, S. steinhauseri, S. polygonalis) are investigated from different biometrical aspects such as depositional environments and biogeographical distribution as well as their systematic palaeontology from two formations (the Tirgan and Sarcheshmeh formations) in nine stratigraphic sections.     

伊拉克底格里斯河摩苏尔河段特性分析

采用天然河道实测资料分析和实验室试验分析方法对伊拉克底格里斯河摩苏尔55km河段的河道床沙组成进行研究,目的是分析河床表层及底层泥沙组成,以及该河段的床沙粗化条件.通过收集天然河道的床沙资料,对沙样进行实验室分析,结果表明:底格里斯河摩苏尔河段床沙已形成粗化:一般河床表层泥沙颗粒大小分布随着河段距离的增加而减小,床沙接近于均勻分布,表层床沙沙样颗粒中圆盘形、 球形、柱形和片状分别为48.34%、25.2%、15.34%和11.08%.在床沙的表层和底层泥沙以粗沙砾石为主,分别为74%和36%.