GIS-based landslide susceptibility mapping using numerical risk factor bivariate model and its ensemble with linear multivariate regression and boosted regression tree algorithms

In this study, a novel approach of the landslide numerical risk factor(LNRF) bivariate model was used in ensemble with linear multivariate regression(LMR) and boosted regression tree(BRT) models, coupled with radar remote sensing data and geographic information system(GIS), for landslide susceptibility mapping(LSM) in the Gorganroud watershed, Iran. Fifteen topographic, hydrological, geological and environmental conditioning factors and a landslide inventory(70%, or 298 landslides) were used in mapping. Phased array-type L-band synthetic aperture radar data were used to extract topographic parameters. Coefficients of tolerance and variance inflation factor were used to determine the coherence among conditioning factors. Data for the landslide inventory map were obtained from various resources, such as Iranian Landslide Working Party(ILWP), Forestry, Rangeland and Watershed Organisation(FRWO), extensive field surveys, interpretation of aerial photos and satellite images, and radar data. Of the total data, 30% were used to validate LSMs, using area under the curve(AUC), frequency ratio(FR) and seed cell area index(SCAI).Normalised difference vegetation index, land use/land cover and slope degree in BRT model elevation, rainfall and distance from stream were found to be important factors and were given the highest weightage in modelling. Validation results using AUC showed that the ensemble LNRF-BRT and LNRFLMR models(AUC = 0.912(91.2%) and 0.907(90.7%), respectively) had high predictive accuracy than the LNRF model alone(AUC = 0.855(85.5%)). The FR and SCAI analyses showed that all models divided the parameter classes with high precision. Overall, our novel approach of combining multivariate and machine learning methods with bivariate models, radar remote sensing data and GIS proved to be a powerful tool for landslide susceptibility mapping.     

Tracing subsurface oil pollution leakage using 2D electrical resistivity tomography

This study provides an evaluation of the subsurface oil contaminant flow in an oil production field at the Wadi Feiran fan, along the Gulf of Suez, Egypt. The 2D electrical resistivity tomography technique has been applied along four profiles surrounding the spill location of oil dump site. Theoretical soil resistivity response versus fluid resistivity for different cation exchange capacity values has been studied. Then, a physical model for the current situation of flowing the oil over the groundwater (sea invaded water) of saturated fluvial sediments has been introduced. It was supposed that the crude oil has higher resistivity values and turned to be conductive far away from the oil spill source under the effect of microbial biodegradation. Such conditions of contaminated distribution and its resistivity values have been considered during the inversion and interpretation of the acquired data sets. The processed 2D resistivity profiles reveal that oil plumes are accumulated in the seawater invasion direction, whereas it has low signatures along the profiles parallel to the shore line.     

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%.     

3D geomodeling of the Lower Cretaceous oil reservoir, Masila oil field, Yemen

Oil was first discovered in the Masila area of Yemen in the late 1990s, with about 90% of the reserves found in the Lower Qishn Clastic Member of the Qishn Formation. The porosity determinations of the Lower Qishn Clastic are relatively high and the permeability ranges from 103 to 374?md. This paper tries to evaluate the hydrocarbons in the porous zones encountered in the Lower Cretaceous formations, which were penetrated by the eight wells in the study area. The water saturation shows low values, while the hydrocarbon saturation is in a reverse relation, i.e., the hydrocarbon increases where the water saturation decreases. Different cross-plots such as Rho-PHIN, Rho-DTN, and M-N were used in lithological identification for the two studied formations (Saar and Qishn) in the studied wells. Formation evaluation and presentation forms of the obtained petrophysical parameters have frequently proven that the formations have high hydrocarbon saturation in this area and contain many pay zones. On of the main targets of this paper is to build a detailed 3D geological modeling of the Lower Cretaceous Sequence conducted through an integrated study.     

Stratigraphy,deposition, and structural framework of the cretaceous (review) and 3D geological model of the lower cretaceous reservoirs,Masila oil field,Yemen

The Masila area is located in the Hadhramaut region in east central Yemen. Oil was first discovered in the area in late 1990 with commerciality being declared in late 1991. Oil production began in July 1993. By the end of December 1999, the daily production rate was set at 210,000 stock tank barrels/day (STB/D) of very low gas–oil ratio (GOR) oil under partial to full water drive. About 90% of the reserves are found in the Lower Qishn Clastics Member of the Qishn Formation. This paper focuses on the detailed 3D geological modeling of the Lower Cretaceous Sequence conducted through an integrated study. There are three critical areas in the process of modeling reservoirs that involve geological and geophysical modeling, reservoir characterization, and reservoir flow modeling. This paper presents methodologies found useful during the modeling of these reservoirs including field case histories for the Lower Cretaceous reservoir in the Masila oilfield.     

Prediction of fish yield and potential productivity from limnological data in Lake Borollus, Egypt

Four limnological models (lake shoreline development (D_L), Morphoedaphic Index (MEI), primary production and total nutrient input) have been applied to Lake Borollus to estimate existing fish yield and future potential productivity. The estimated existing fish yield from the lake is about 1260 kg/ha (i.e. 53,000 tons/annum), which is at or near its existing potential and is considered in the ultra enriched category. From 1931 to 1935, the estimated fish production of Lake Borollus was about 68 kg/ha, which is considered low enriched category, while from1960 to 1970, the lake belonged to the moderately enriched category, where the estimated fish production was about 155 kg/ha, and then tremendously increased to about 580 kg/ha during the 1980's.Thisincrease in fish yield is mainly attributed to the nutrient loading of the southern and eastern drains to the lake. In the long term, and based on existing nutrient input to fish yield relationships, it is estimated that increased nutrient loading from drainage water may elevate its yield by 24, 580 tons by the year 2005 (i.e. total fish yield could be increased to 77,500 tons/annum). This revised version was published online in July 2006 with corrections to the Cover Date.     

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.