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51.
Tidal inundation mapping under enhanced land subsidence in Semarang,Central Java Indonesia 总被引:3,自引:0,他引:3
Tidal inundation by high tide under enhanced land subsidence is a damaging phenomenon and a major threat to the Semarang urban
area in Indonesia. It impacts on economic activities, as well as the cost of an emergency program and causes interruption
of pubic services, danger of infectious diseases and injury to human lives. This study examines a spatial analysis tool on
the GIS-raster system for the tidal inundation mapping based on the subsidence-benchmark data and modified detail digital
elevation model. Neighborhood operation and iteration model as a spatial analysis tool have been applied in order to calculate
the encroachment of the tidal inundation on the coastal area. The resulting map shows that the tidal flood spreads to the
lowland area and causes the inundation of coastal settlement, infrastructure, as well as productive agricultural land, i.e.,
the fish-pond area. The monitoring of the vulnerable area due to the tidal inundation under the scenario of extended land
subsidence plays an important role in long-term coastal zone management in Semarang. 相似文献
52.
The state of land subsidence and prediction approaches due to groundwater withdrawal in China 总被引:13,自引:6,他引:7
This article gives a general introduction to land subsidence with the prediction approaches due to withdrawal of groundwater
in three subsided/subsiding regions in China: the deltaic plain of Yangtse River (YRDP), North China Plain (NCP), and Fenwei
Plain (FP). On YRDP, Shanghai is the typical subsided/subsiding city; on NCP Tianjin is the typical subsided/subsiding city,
and on FP Taiyuan is the typical subsided/subsiding city. The subsided area with subsidence over 200 mm on YRDP is about 10,000 km2 and the maximum subsided value reached 2.9 m at Shanghai; on NCP the subsided area reached 60,000 km2 with the maximum subsidence of 3.9 m at Tianjing; on FP the subsided area is relatively smaller than that on the other two
plains and is about 1,135 km2 with maximum subsidence of 3.7 m at Taiyuan city. In order to protect the civil and industrial facilities, it is necessary
to predict the future development of land subsidence based on present state. Many researchers proposed several approaches
to predict the land subsidence due to groundwater withdrawal according to different geological conditions and groundwater
withdrawal practice. This article classifies these approaches into five categories: (i) statistical methods; (ii) 1D numerical
method; (iii) quasi-3D seepage model; (iv) 3D seepage model; (v) fully coupled 3D model. In China, the former four categories
are presently employed in the prediction practice and their merits and demerits are discussed. According to the prediction
practice, 3D seepage model is the best method presently. 相似文献
53.
The concentrations of twenty four chemical elements in the surface layer of natural desert soils and the cultivated farmland soils were measured at a desert-oasis ecotone in the middle of Heihe river basin, north-west China. Background values were estimated for (a) major elements (Si 335.3 g kg− 1, Al 49.4 g kg− 1, Fe 19.1 g kg− 1, Ca 29.4 g kg− 1, Mg 8.9 g kg− 1, K 20.1 g kg− 1, Na 17.5 g kg− 1 and P 0.338 g kg− 1), (b) heavy metals and non-metals (Cr 55.8 mg kg− 1, Mn 404.8 mg kg− 1, Ni 17.7 mg kg− 1, Cu 5.1 mg kg− 1, Zn 33.7 mg kg− 1, Pb 15.5 mg kg− 1 and As 5.2 mg kg− 1) and (c) other trace elements (Ti 2.0 mg kg− 1, V 55.3 mg kg− 1, Co 5.7 mg kg− 1, Rb 82.4 mg kg− 1, Sr 232.9 mg kg− 1, Y 14.7 mg kg− 1, Zr 194.9 mg kg− 1, Nb 7.8 mg kg− 1 and Ba 720.6 mg kg− 1). After natural desert soil was cultivated for agricultural use, significant changes in element concentrations occurred under tillage, irrigation and fertilisation management. Compared to natural soil, the for the levels of Si, K, Na, Sr, Zr and Ba decreased, and no changes were observed for Rb, while the values of the other 17 elements increase in agricultural soil from 1.2 to 3.5 times. However, their absolute concentrations are still low, suggesting that the arable soil in this region remains comparatively a clean soil. The increased silt, clay and organic carbon content, under long-term irrigation, enriched the fine-grained materials, and application of fertilisers and manure contributed to the accumulation of most elements in arable soil. The accumulation of elements in agricultural soil increased with increasing cultivation years and extent of soil development. 相似文献
54.
This article describes a unique flood hazard, produced by the dramatic expansion of wetlands in Nelson County, located within
the North American Prairie Pothole Region of North Dakota, USA. There has been an unprecedented increase in the number, average
size, and permanence of prairie wetlands, and a significant increase in the size of a closed lake (Stump Lake) due to a decade-long
wet spell that began in 1993 following a prolonged drying trend. Base-line land cover information from the 1992 USGS National
Land Cover Characterization dataset, and a Landsat TM scene acquired 9 July 2001 are used to assess the growth of the closed
lake and wetland pond surface areas, and to analyze the type and area of various land cover classes inundated between 1992
and 2001. The open water profile in Nelson County changed from one marked by relatively comparable coverage of closed lake
and wetland pond areas in 1992, to one in which wetland open water accounted for the vast majority of total open water in
2001. The bulk of the wetland pond area expansion occurred by displacing existing wetland vegetation and agricultural cropland.
Producers responded to the flood hazard by filing Federal Crop Insurance Corporation (FCIC) claims and enrolling cropland
in the Conservation Reserve Program (CRP), a federal land retirement program. Land taken out of agricultural production has
had an enormous impact upon the agricultural sector that forms the economic base of the rural economy. In 2001 the land taken
out of production due to CRP enrollment and preventive planting claims represented nearly 42% of Nelson County’s 205.2 K ha
base agricultural land. The patterns obtained from this detailed study of Nelson County are likely to be the representative
of the more publicized flood disaster occurring within the Devils Lake Basin of North Dakota. 相似文献
55.
There could be some discontinuities in a soil media such as layers, earth structures, cracks, and fissures so that estimation
of stresses and deformations in these types of soil masses are somewhat different from continuous masses. The discontinuities
in a soil mass could be considered as a special link between two blocks. Transmitted swelling pressures affected by the soil
properties of the backfill especially at the interface between the backfill and retaining wall. In order to estimate the transmitted
swelling pressure distribution behind a retaining wall, using with interface element, a new finite element model and a code
(SWELPRES) have been developed. To evaluate the effect of backfill characteristics and interface element from the transmitted
lateral swelling pressures, four cases of thickness of backfills with or without interface elements are investigated. 相似文献
56.
西藏西南部拉昂错地幔橄榄岩的地球化学特征及其构造意义 总被引:2,自引:0,他引:2
拉昂错蛇绿岩位于西藏西南部雅鲁藏布缝合带(YZSZ)的西段,由地幔橄榄岩和侵入其中的基性岩墙组成.拉昂错地幔橄榄岩普遍发育碎斑结构及熔体注入和交代结构,尖晶石的Cr#值具有较广泛的变化(0.32~0.70),大多数样品富集LREE并伴随HFSE的明显增加,少数亏损LREE,前者部分熔融程度为15%~23%,后者为10%左右,这表明它们并不是地幔单阶段部分熔融的残余物,而是MORB型亏损橄榄岩在俯冲过程中再度部分熔融后熔体与残余地幔相互作用的产物,由于熔体不同程度的混合与交代,形成了各种再饱满程度不同的橄榄岩.对拉昂错地幔橄榄岩岩石学和地球化学特征的研究,为探讨YZSZ蛇绿岩带所代表的特提斯洋盆的形成和演化提供了新的证据. 相似文献
57.
本文以赤道东太平洋海温作为主导因子,分析其与东亚温带气旋的关系。得出:高海温多气旋,低海温少气旋的对应关系较为明显。并进一步对不符合这种主要关系的年份从环流型。下垫面海温等作了分类鉴别分析。 相似文献
58.
本文对大气运动中垂直速度w计算中的几种校正方法作了分析比较,并在前人工作的基础上,对校正方法作了改进,提出了进行低通滤波、散度校正和法线风分量校正的方法。通过这些校正,使计算出的平均散度和垂直速度的垂直廓线能维持原计算曲线的形式,并能满足整个气层连续方程积分为零的条件,也符合误差随高度增大的情况。 相似文献
59.
60.
Toru?Iwata Keiko?Yoshikawa Katsutoshi?Nishimura Yoshihisa?Higuchi Takao?Yamashita Shigeru?Kato Eiji?OhtakiEmail author 《Journal of Oceanography》2004,60(6):995-1000
The measurements of the vertical transport of CO2 were carried out over the Sea of Japan using the specially designed pier of Kyoto University on September 20 to 22, 2000. CO2 fluxes were measured by the eddy correlation and aerodynamic techniques. Both techniques showed comparable CO2 fluxes during sea breeze conditions: −0.001 to −0.08 mg m−2s−1 with the mean of −0.05 mg m−2s−1. This means that the measuring site satisfies the fetch requirement for meteorological observations under sea breeze conditions. Moreover, the eddy diffusivity coefficient used in the aerodynamic technique is found to be consistent with the coefficient used in the eddy correlation technique. The present result leads us to conclude that the aerodynamic technique may be applicable to underway CO2 flux measurements over the ocean and may be used in place of the bulk technique. The important point is the need to maintain a measuring accuracy of CO2 concentration difference of the order of 0.1 ppmv on the research vessels or the buoys. 相似文献