绵竹市清平乡芍药沟泥石流危险性评价分析

5.12汶川8.0级地震后,引发了大规模的震后灾害,绵竹市清平乡芍药沟在地震影响下,先后发生了3次大规模的突发泥石流,对流域沟口处的二级电站厂房威胁较大,且相关人员的安全也受此影响.本文在野外调查的基础上,利用单沟泥石流法对芍药沟泥石流进行研究分析,以确定泥石流的危险程度等级.研究发现:区内总物源量达16.84万m3,...     

渝东北典型盆缘山区高位崩滑灾害风险评价

研究区位于重庆市巫溪县下堡镇内,属渝东盆缘山区,地形切割强烈,地质环境复杂,地质灾害频发。为了研究高陡峡谷区地质灾发育分布规律、风险区划,文章选取高程、坡度、坡向、工程地质岩组、距水系距离及距褶皱距离因子做为地质灾害易发性评价的影响因素,基于ArcGIS平台,利用信息量模型,定量评价了巫溪宁桥片区高陡峡谷区高位地质灾害的易发性,评价模型与地质灾害分布空间契合度较高,评价结果可信度较高。再结合易损性评价对研究区进行了地质灾害风险评价,最终得到研究区地质灾害风险评价模型。为该区域地质灾害防治提供了科学依据,同时对同类高陡峡谷地区地质灾害风险性评价及地质灾害防治具有借鉴意义。     

绵竹清平8·13群发泥石流成因、特征与发展趋势

2010年8月13日凌晨,5·12汶川地震极重灾区绵竹市清平乡发生群发泥石流灾害,27条沟谷发生泥石流,占泥石流沟总数的69.4%,其中以文家沟泥石流最为严重。在调查基础上,分析了8·13特大群发泥石流的成因、特征和发展趋势,并提出了灾后规划重建中的地质安全问题。从成因上看,8·13特大群发泥石流是5·12汶川地震和强降雨共同作用的结果;从特征上来看,泥石流呈现出暴发空间的群发性、启动过程的复杂性、发生过程的持续性,成灾过程的链式性、危害形式的多样性、泥石流规模的放大性和泥石流隐患的隐蔽性等7个方面的特征;清平乡各沟8·13泥石流冲出方量约占物源总量的10%～50%,泥石流存在进一步频发、群发的态势,建议在灾后规划重建的过程中,应全面科学评估清平乡泥石流灾害的链式效应和地质环境容量问题,将地质灾害的防治同规划重建密切结合。     

地质灾害威胁下的农村居民点用地适宜性评价——以彭州市银厂沟流域为例

目前针对受震灾威胁、地质灾害频发的山地环境下的农村居民点布局研究尚不多见。该文以彭州市龙门山镇银厂沟流域为例,首先在总结分析区内地质灾害发育特征的基础上,基于8项指标进行地质灾害危险性分区; 然后,将地质灾害危险性区划结果作为影响农村居民点用地适宜性评价的首要因素,再结合地形条件、社会经济和生态环境等方面,以地质灾害极高危险区、单体地质灾害危害范围、坡度≥25°和基本农田保护区为限制性条件,构建地质灾害威胁下的农村居民点用地适宜性评价指标体系; 最后,采用模糊综合评价法对彭州市银厂沟流域内居民点用地适宜性进行评价分级。研究结果表明: 高度适宜区占研究区总面积的4.2%,中度适宜区占11.4%,低度适宜区占10.5%,不适宜区占73.8%; 农村居民点用地“适宜”区域主要沿公路分布,并存在多个“块状”集中分布区,这些地区地形平坦,交通条件便利,可为新农村住宅位置的选择提供指导意见。     

Suitability evaluation of rural residential areas under the threat of geological disasters:A case study in Yinchanggou watershed of Pengzhou City

At present, the research on the layout of rural residential areas in the mountainous environment under the threat of earthquake disasters and frequent geological disasters is still rare. Taking Yinchanggou watershed in Longmenshan Town of Pengzhou City as an example, based on the summary of the geological hazard development characteristics in this area, the authors carried out the hazard risk zoning through 8 indexes. Then the geological hazard risk zoning was used as the primary factor to evaluate the suitability of rural residential areas. Besides, combined with the topographical conditions, socio-economic situation and ecological environment, a suitable evaluation index system for rural residential land under the threat of geological disasters was constructed, with the restrictive conditions of extremely high-risk areas, single geological hazards, slopes ≥25° and basic farmland protection areas. Finally, the fuzzy comprehensive evaluation method was used to evaluate the suitability of residential land in Yinchanggou watershed of Pengzhou City. The results show that high suitability areas account for 4.2% of the total area of the study area, moderate suitability areas 11.4%, low suitability areas 10.5%, and unsuitable areas 73.8%. The “suitable” areas for rural residential land are mainly distributed along the highway, and some are multiple “blocky” concentrated distribution areas. The terrain is flat and the traffic condition is convenient, which can provide some guidance for the selection of new rural residential locations.     

Quantifying the impact of human activities on geological hazards in mountainous areas: evidence from Shennongjia,China

An increasing number of geological hazards threaten human life and property in mountainous areas, especially in China. Existing studies on the prevention of geological hazards mainly focus on natural factors and ignore the impact of human activities on geological hazards. This study aims to enrich our knowledge of the impact of human activities through a case study from the Shennongjia mountainous area, China. Spatial regression models were used to quantify the impact of different construction activities on geological hazards based on remote sensing images, local statistical data, land-use data and geological hazards distribution data. The Shennongjia case revealed the following: (1) The global Moran’s I index of the distribution of geological hazards was 0.35, which showed obvious spatial autocorrelation characteristics. (2) From the multiple model comparison, the spatial lag model was more suitable for quantifying the impact of human activities on geological hazards than the least squares regression model and the spatial error model. (3) Road construction and building construction were the main causes of geological hazards, whereas agricultural activities and mining activities had only a limited effect. The evidence reported here could enable governments to constrain human activities and to reduce the geological hazards in mountainous areas across China and beyond.     

The impact of crustal rheology on natural seismicity: Campi Flegrei caldera case study

We analyze the crustal rheology beneath the active resurgent Campi Flegrei caldera(CFc) in Southern Italy by modelling the 3 D brittle-ductile(B/D) transition, based on available thermal, geological and geophysical data. Firstly, the thermal field in the conductive physical regime is modeled using a finite element method; based on an optimization tool, this method is applied to evaluate the location and dimensions of the deep thermal source beneath the caldera. A horizontally-extended thermal anomaly located at about 5000 m depth below sea level is identified beneath Pozzuoli Bay, a part of the CFc. The same isotherm is located at a depth of 20,000 m beyond the caldera. This indicates a higher horizontal temperature gradient in the caldera with respect to the surrounding area. Next, we utilize this thermal model to image the 3D rheological stratification of the shallow crust below the caldera with two different values of strain rates. Within the caldera, the B/D transitions with ε equal to 10^-12 s^-1 and 10^-8 s^-1 are located at 3000 m and 5000 m depths, respectively. Outside the caldera, the transition is very deep(15,000-20,000 m), seemingly uninfluenced by the thermal state of the CFc volcanism. Finally, we compare these results with the spatial distribution of earthquake hypocenters, Benioff strain release and b-value distribution to investigate the relationship between crustal rheology and seismicity characteristics. Our analysis reveals that the image of the B/D transition is in agreement with the distribution of earthquake hypocenters, constraining the potential seismogenic volume of the region. Our study demonstrates that knowledge of the rheological state of a volcanic system is an important element to interpret its dynamic, forecast future activity and improve evaluation of the associated seismic hazard.     

Large-scale natural disaster risk scenario analysis: a case study of Wenzhou City, China

Based on the analysis and calculation of the hazard intensity of typhoon rainstorms and floods as well as the vulnerability of flood receptors and the possibility of great losses, risk scenarios are proposed and presented in Wenzhou City, Zhejiang Province, China, using the Pearson-III model and ArcGIS spatial analyst tools. Results indicate that the elements of risk scenarios include time–space scenarios, disaster scenarios, and man-made scenarios. Ten-year and 100-year typhoon rainstorms and flood hazard areas are mainly concentrated in the coastal areas of Wenzhou City. The average rainfall across a 100-year frequency is 450 mm. The extreme water depth of a 100-year flood is 600 mm. High-vulnerability areas are located in Yueqing, Pingyang, Cangnan, and Wencheng counties. The average loss rate of a 100-year flood is more than 50%. The greatest possible loss of floods shows an obvious concentration-diffusion situation. There is an area of about 20–25% flood loss of 6–24 million Yuan RMB/km² in the Lucheng, Longwan and Ouhai districts. The average loss of a 100-year flood is 12 million Yuan RMB/km², and extreme loss reaches 49.33 million Yuan RMB/km². The classification of risk scenario may be used for the choice of risk response priorities. For the next 50 years, the 10-year typhoon rainstorm-flood disaster is the biggest risk scenario faced by most regions of Wenzhou City. For the Yueqing, Ruian, and Ouhai districts, it is best to cope with a 100-year disaster risk scenario and the accompanying losses.     

Assessment of social vulnerability to natural disasters: a comparative study

The purpose of this study is to examine and compare the methodologies being developed in assessing social vulnerability to natural disasters. Existing vulnerability literature shows that two methods have been used in developing social vulnerability indexes: (1) a deductive approach based on a theoretical understanding of relationships and (2) an inductive approach based on statistical relationships (Adger et al. in New indicators of vulnerability and adaptive capacity. Tyndall Centre for Climate Change Research, Norwich, 2004). Two techniques were also utilized in aggregating social vulnerability indicators: (1) a deductive approach using standardization techniques such as z scores or linear scaling (Wu et al. in Clim Res 22:255?C270, 2002; Chakraborty et al. in Nat Hazards Rev 6(1):23?C33, 2005) and (2) an inductive approach using data-reduction techniques such as factor analysis (Clark et al. in Mitig Adapt Strateg Glob Change 3(1):59?C82, 1998; Cutter et al. Soc Sci Quart 84(2):242?C261, 2003). This study empirically compares deductive and inductive index development and indicator aggregation methods in assessing social vulnerability to natural disasters in the Gulf of Mexico and Atlantic coastal areas. The aggregated social vulnerability index is used to examine a relationship with disaster losses in the Gulf of Mexico and Atlantic coastal areas. The results show that coastal counties with more vulnerability in terms of social achieved status are positively associated with disaster damages, while variations in the development of the index using deductive and inductive measurement approaches produce different outcomes.     

Integrated natural disasters urban resilience evaluation: the case of China

Natural Hazards - China is one of the countries affected most by natural hazards. With the rapid urbanization process, the susceptibility of Chinese cities to natural disasters increases. In this...     

Dietary pattern recognition on Twitter: a case example of before,during, and after four natural disasters

Natural Hazards - Little is known about what foods/beverages (F&B) are common during natural disasters. The goal of this study was to track high-frequency F&B mentions during four...     

Daily rainfall erosivity as an indicator for natural disasters: assessment in mountainous regions of southeastern Brazil

Natural Hazards - Rainfall erosivity is defined as the rainfall potential to cause erosion. Its concept is based on the kinetic energy of rainfall, rainfall intensity, and maximum rainfall...     

山区城市地质灾害与经济发展的关系研究——以兰州市为例

兰州市是中国乃至世界上滑坡、泥石流等地质灾害最为严重的山区城市之一, 区内地质灾害问题十分突出, 防灾减灾任务繁重. 地质灾害是影响社会经济发展的因素之一, 地质灾害与城市经济的发展相伴共生, 相互制约、相互促进. 运用灾害统计学、经济学中的哈罗德-多马模型、脱钩模型等多种理论方法对2006-2012年兰州市地质灾害与经济发展的关系进行分析. 结果表明: 兰州市地质灾害总体上对经济发展的影响仍以负面影响为主, 正面影响对经济的促进作用相对较弱; 近年来地质灾害防灾减灾效果明显, 已取得了良好的社会效益、经济效益和环境效益. 在区内地质灾害高发和社会经济持续稳定增长共生的条件下, 必须以实现"地质灾害的负增长"为当前和今后一段时期防灾减灾的重要任务和目标, 最终达到地质灾害的有效防治与社会经济的可持续协调发展.     

Socioeconomic development and the impact of natural disasters: some empirical evidences from China

Significant advancements have been made in examining the relationship between economic development and disaster losses at the global and national scales, but very little research has been done at the sub-national level, especially in China. Based on socioeconomic and disaster impact data from 31 provinces (municipalities, and autonomous regions) in China from 1990 to 2010, ordinary least squares regression was used to determine the relationship between socioeconomic development and effects of natural disasters. Results showed that economic development played a distinct role in mitigating disaster damages in the whole China and its eastern, central and western regions. There existed a U-shaped relationship between economic growth and disaster losses in the whole China and its eastern region, and an inverted-U nonlinearity linkage in its central and western areas. These findings further confirmed the existence of a nonlinear relationship between economic development and disaster losses. Economic growth had played a more important role in mitigating disaster losses in the central region of China than that in the western one. Further investigations demonstrated that as economic develops, there were fewer deaths caused by natural hazards in whole China and all its three regions. The combination of the lower level of education, higher unemployment rate and greater gross dependence ratio has contributed to the increase in death toll caused by natural disasters, but this trend could be partly offset by wealth growth.     

综合电法在岩溶山区地下水勘探中的应用——以湖南怀化长塘村为例

岩溶山区水文地质条件复杂,地下水的分布规律对不同的物探方法可能存在不同的响应特征。综合采用高密度电阻率法和音频大地电磁法,在湖南怀化长塘村进行找水勘探,综合勘探结果很好地指示出异常特征和比较具体的异常位置。推断结果与钻井结果基本一致,最大涌水量大于146.88 m³/d/。此次成果表明:对称四极反演结果能有效对地下横向电阻率的变化进行响应,且纵向上能够利用电阻率测深曲线(单支曲线)进行分层;音频大地电磁法探测深度大,能有效对地下断层构造进行响应。     

Formation and characteristics of post-earthquake debris flow: a case study from Wenjia gully in Mianzhu, Sichuan, SW China

During the three flood seasons following the Wenchuan earthquake in 2008, two catastrophic groups of debris flow events occurred in the earthquake-affected area: the 2008-9-24 debris flow events, which had a serious impact on rebuilding; and the 2010-8-13/14 debris flow events, which destroyed much of the progress made in rebuilding. The Wenjia gully is a typical post-earthquake debris flow gully and at least five debris flows have occurred there. As far as the 2010-8-13 debris flow is concerned, the deposits of the Wenjia gully debris flow reached a volume of 3.1 × 10⁶ m³ in volume and hundreds of newly built houses were buried. This study took the Wenjia gully debris flow as an example and discussed the formation and characteristics of post-earthquake debris flow on the basis of field investigations and a remote sensing interpretation. The conclusions drawn from the investigation and analysis were as follows: (1) Post-earthquake debris flows were a joint result of both the earthquake and heavy rainfall. (2) Gully incision and loose material provision are key processes in the initiation and occurrence of debris flows and a cycle can be presented as the following process: runoff—erosion—collapse—engulfment—debris flow—further erosion—further collapse—further engulfment—debris flow enlargement. (3) The amount of rainfall that triggered debris flows from the Wenjia gully was significantly less than the average daily rainfall, while the intraday rainfall threshold decreased by at least 23.3%. (4) The occurrence mechanism of Wenjia gully debris flow was an erosion type and there was a positive relationship between debris flow magnitude and rainfall, which fitted an exponential model. (5) There were five representative characteristics of Wenjia gully debris flow: the long duration of the occurring process; the long distance of deposition chain conversion during the process of damage; magnification in the scale of debris flow; and the high frequency of debris flow events.     

筑坝对山区河流碳动力学的影响

流域的地貌和气候特征及干流筑坝等是影响河流碳动力学的主要因素。本文对干流下游筑坝的华南山地丘陵区河流增江的碳循环过程做了系统研究。结果表明,山地丘陵为主的流域地貌特征提高了增江河流碳的输出通量;而亚热带湿润气候和较高的森林覆盖率以及缺乏碳酸盐岩的流域地质背景使得溶解有机碳（DOC）构成增江河流碳的主要成分;光化学分解可以解释在秋季较强紫外线辐射下河水较低的DOC含量。受大坝影响河段水流速度的变缓为水生生物量的增加提供了条件,使得颗粒有机碳（POC）中来源于水生生物量的贡献率上升、有机物的C/N比降低。流速变缓的河道中藻类的生长导致水体CO₂分压低于大气中的CO₂分压。增江流域DOC和POC的输出通量分别为25.08×10⁵g/km²·a和11.58×10⁵g/km²·a。本文为研究自然因素和人类活动对河流碳循环过程及通量的影响提供了一个典型案例。