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891.
流域土地覆被变化水文效应的模拟——以长江上游源头区梭磨河为例 总被引:43,自引:3,他引:40
为分析地表覆被变化的水文效应,以半分布式的地形指数模型 (TOPOMODEL) 为基础,对梭磨河流域1960~1999年逐日流量过程进行了模拟。结果表明,对于流域面积2536km2 的梭磨河流域,该模型也能取得较好的模拟结果。模拟了流域40年来气候波动和地表覆被变化对流域水文的影响。最后在4种不同的流域土地覆被情景下模拟了1960~1999年逐日径流过程。对于实际蒸散发与潜在蒸发有300多mm差距的梭磨河流域,在其它条件不变的情况下,随着流域土地覆被和冠层最大截流量的增加,冠层截流蒸发和流域总蒸发增加,植被蒸腾和土壤表面蒸发减少,土壤水分增加而流域水分含量和饱和层含水量减少。地表径流、地表以下径流、总径流减小。重现期小于20年的洪峰流量减小,但对40年一遇的洪峰流量影响很小,甚至有增加洪峰流量的作用。 相似文献
892.
奥布公路泥石流危险性评价 总被引:1,自引:0,他引:1
作为喀喇昆仑公路的重要组成部分,奥依塔克-布伦口(简称奥布)公路受到沿线数量众多且规模较大的泥石流影响,常导致行车中断,人员和车辆安全受到威胁。在现场地质考察和走访基础上,依据ArcGIS工具对奥布公路段的15条典型泥石流沟开展了重点调查和危险性评价。首先对汇流面积、纵坡度、面积宽度比、堆积区面积和距公路距离等5个评价因子属性进行归一化处理;然后采用两层结构的层次分析法计算得到影响因子的权重,随后将属性函数与权重乘积加和,得到灾害易发性指数(DFRD);最后对泥石流危险度(DRFR)进行计算分析和危险程度分级。结果发现,高-中度危险的11条泥石流主要分布在布伦口峡谷上游、盖孜检查站和加水沟之间,构成了泥石流灾害发育较为集中且危害性较大的路段。工程上相应采用隧道、高架桥等绕避措施,取得较好成效。 相似文献
893.
Predicting landslides for risk analysis — Spatial models tested by a cross-validation technique 总被引:3,自引:3,他引:0
A landslide-hazard map is intended to show the location of future slope instability. Most spatial models of the hazard lack reliability tests of the procedures and predictions for estimating the probabilities of future landslides, thus precluding use of the maps for probabilistic risk analysis. To correct this deficiency we propose a systematic procedure comprising two analytical steps: “relative-hazard mapping” and “empirical probability estimation”. A mathematical model first generates a prediction map by dividing an area into “prediction” classes according to the relative likelihood of occurrence of future landslides, conditional by local geomorphic and topographic characteristics. The second stage estimates empirically the probability of landslide occurrence in each prediction class, by applying a cross-validation technique. Cross-validation, a “blind test” here using non-overlapping spatial or temporal subsets of mapped landslides, evaluates accuracy of the prediction and from the resulting statistics estimates occurrence probabilities of future landslides. This quantitative approach, exemplified by several experiments in an area near Lisbon, Portugal, can accommodate any subsequent analysis of landslide risk. 相似文献
894.
Interaction of waves,currents and tides,and wave-energy impact on the beach area of Sylt Island 总被引:3,自引:1,他引:2
Erosion due to waves is an important and actual problem for most coastal areas of the North Sea. The objective of this study
was to estimate the impact of wave action on the coastline of Sylt Island. From a 2-year time series (November 1999 to October
2001) of hydrological and wave parameters generated with a coupled wave–current modelling system, a period comprising storm
‘Anatol’ (3–4 December 1999) is used to investigate the effects of waves on currents and water levels and the input of wave
energy into the coastline. The wave-induced stress causes an increase of the current velocity of 1 m/s over sand and an additional
drift along the coast of about 20 cm/s. This produces a water level increase of more than 20 cm in parts of the tidal basin.
The model system also calculates the wave energy input into the coastline. Scenario runs for December 1999 with a water level
increase of 50 cm and wind velocity increased by 10% show that the input of the wave energy into the west coast of Sylt Island
increases by 30% compared to present conditions. With regard to the forecasted near-future (Woth et al., Ocean Dyn 56:3–15,
2006) increase of strong storm surges, the scenario results indicate an increased risk of coastal erosion in the surf zone of
Sylt Island. 相似文献
895.
896.
研究震灾风险认知及其影响因素有助于从公众视角揭示风险潜在因素,为降低灾害风险提供决策依据.本文以新疆的喀什、乌鲁木齐为研究区,通过问卷调查方式,采用假设检验和相关分析等统计方法,研究影响公众的临震心理、风险估计、地震知识水平、防震意愿及行为等震灾风险认知的因素.结果表明:影响因素包括性别、教育水平、收入水平、家庭结构、房屋结构、居住区危险性等;因素之间互相联系与风险认知因子形成正、负反馈链,其中收入水平影响了风险感知是否能转化为防减灾的积极行为.并在灾害风险分析的基础上提出了减轻地震灾害风险的对策建议. 相似文献
897.
Hamid Zafarani Assadollah NoorzadAnooshirvan Ansari Khosro Bargi 《Soil Dynamics and Earthquake Engineering》2009
Strong-motion data from eight significant well-documented earthquakes in Iran have been simulated using a stochastic modeling technique for finite faults proposed by Beresnev and Atkinson [Bull Seismol Soc Am 87 (1997) 67–84; Seism Res Lett 69 (1998) 27–32]. The database consists of 61 three-component records from eight earthquakes of magnitude ranging from M 6.3 to M 7.4, recorded at hypocentral distances up to 200 km. The model predictions are in good agreement with available Iranian strong-motion data as evidenced by near-zero average of differences between logarithms of the observed and predicted values for all frequencies. The strength factor, sfact, a quantity that controls the high-frequency radiation from the source is determined, on an event-by-event basis, by fitting simulated to observed response spectra. 相似文献
898.
The region stricken by the Irpinia earthquake (Ms=6.9) on 1980, along the Southern Appenninc chain, is one of the highest seismic hazard areas of Italian peninsula. 相似文献
899.
GIS-based risk assessment of grassland fire disaster in western Jilin province, China 总被引:4,自引:2,他引:2
Tong Zhijun Zhang Jiquan Liu Xingpeng 《Stochastic Environmental Research and Risk Assessment (SERRA)》2009,23(4):463-471
Grassland fire disasters have occurred frequently and adversely affected livestock agriculture and social-economic development
greatly in the grassland regions of Jilin province, China. Moreover, both the frequency of grassland fire and loss from them
are considered to be increasing with the global warming and economic development. This study presents a methodology for risk
analysis and assessment of grassland fire disaster, taking western Jilin province as a case study area based on geographic
information system (GIS). The composite grassland fire disaster risk index (GFDRI) combined the hazard of grassland fire,
the exposure of the region, the vulnerability and emergency response and recovery capability for grassland fire disaster of
the region were developed to assess and compare risk of grassland fire disaster in different counties in western Jilin province,
China using the natural disaster risk index method (NDRIM), analytic hierarchy process (AHP) and weighted comprehensive method
(WCM). Then, the risk degree of grassland fire disaster was assessed and regionalized in the western Jilin province, China
based on GFDRI by using GIS. It is shown that the most places of western Jilin province were in mediate risk. Zhenlai, Tongyu
were in heavy risk. Taobei, Ningjiang, Fuyu were in light risk. The information obtained from interviewing the district official
committees in relation to result compiled was statistically evaluated. The GFDRI was developed to be an easily understandable
tool that can be used to assess and compare the relative risk of grassland fire disaster in different counties in t western
Jilin province, China, and to compare the different relative contributions of various factors, e.g., frequency of grassland
fire and quality of emergency evacuation plan. The GFDRI is specifically intend to support local and national government agencies
of grassland fire disaster management as they (1) make resource allocation decisions; (2) make high-level planning decisions;
and (3) raise public awareness of grassland fire disaster risk, its causes, and ways to manage it. 相似文献
900.
Premkumar Thodi Faisal Khan Mahmoud Haddara 《Stochastic Environmental Research and Risk Assessment (SERRA)》2009,23(6):793-809
The deterioration of the condition of process plants assets has a major negative impact on the safety of its operation. Risk
based integrity modeling provides a methodology to quantify the risks posed by an aging asset. This provides a means for the
protection of human life, financial investment and the environmental damage from the consequences of its failures. This methodology
is based on modeling the uncertainty in material degradations using probability distributions, known as priors. Using Bayes
theorem, one may improve the prior distribution to obtain a posterior distribution using actual inspection data. Although
the choice of priors is often subjective, a rational consensus can be achieved by judgmental studies and analyzing the generic
data from the same or similar installations. The first part of this paper presents a framework for a risk based integrity
modeling. This includes a methodology to select the prior distributions for the various types of corrosion degradation mechanisms,
namely, the uniform, localized and erosion corrosion. Several statistical tests were conducted based on the data extracted
from the literature to check which of the prior distributions follows data the best. Once the underlying distribution has
been confirmed, one can estimate the parameters of the distributions. In the second part, the selected priors are tested and
validated using actual plant inspection data obtained from existing assets in operation. It is found that uniform corrosion
can be best described using 3P-Weibull and 3P-Lognormal distributions. Localized corrosion can be best described using Type1
extreme value and 3P-Weibull, while erosion corrosion can best be described using the 3P-Weibull, Type1 extreme value, or
3P-Lognormal distributions. 相似文献