【作者】 铁永波；

【导师】 唐川；

【作者基本信息】 成都理工大学 ， 环境地质， 2009， 博士

【摘要】 2008年5月12日发生在四川省汶川县的里氏8.0级地震不仅造成了重大的人员伤亡和巨额的财产损失,同时也对震区的生态环境造成了严重的破坏,给当地灾后重建进程、生态建设和社会可持续发展带来了严峻的挑战。“5.12”汶川特大地震孕育了不计其数的滑坡、崩塌及潜在不稳定斜坡等不良地质体,为震区内泥石流的孕育及发生提供了有利条件。据“5.12”汶川大地震后的初步统计资料显示,震区新增地质灾害点5千余处(个)。其中常见的四种地质灾害崩塌、滑坡、泥石流及不稳定斜坡总数的97%以上。据震区44个重灾县(市)的次生地质灾害排查结果显示,震区发育有潜在泥石流沟873条,其中潜在的巨型泥石流沟90条、大型泥石流沟91条、中型泥石流沟300条、小型泥石流沟355条。据国土资源系统组织的震后次生地质灾害排查和巡查,四川震区有24座县级城市遭受潜在泥石流隐患点的直接威胁,此外,还有100余处集镇受到不同程度威胁。2008年9月24日,仅距“5.12”汶川大地震四个多月,在这次地震的主要震区北川、汶川等县境内爆发了区域性的泥石流灾害,共造成40余人遇难或失踪,数千亩良田及房屋被冲毁和淤埋的重大灾情,震区泥石流规模之大、破坏力之强,是其它地区泥石流灾害无法比拟的。这次区域性的泥石流灾害表明,“5.12”汶川震区泥石流已进入一个新的活跃期,在未来5-10年内,泥石流将成为震区内最主要的地质灾害之一。如何对震区内已发生或潜在的泥石流灾害开展风险评价是灾后重建中必需面对的一大难题。因此,开展强震区城镇泥石流灾害风险评价方法与体系研究对灾区恢复重建及防灾减灾规划具有重要的理论和实践意义。鉴于目前国内尚未有针对强震区泥石流灾害风险评价的系统研究成果,论文基于地质学、地貌学、系统科学及管理学等相关学科理论及国内外研究进展及动态的基础上,通过对“5.12”汶川大地震强震区之一的北川县大量已发生的泥石流开展调查、结合高分辨率遥感影像资料(分辨率为0.5m)对泥石流沟的遥感解译,开展了系统的强震区城镇泥石流灾害风险评价的方法与体系研究。论文在风险评价的基础上(危险性和易损性),融入了承灾体的承灾能力这一因素,提出了强震区风险评价的方法与体系。通过对风险评价指标的构建,在Arcview等软件的辅助下,开展了强震区城镇泥石流灾害风险评价研究,形成了一套集数据收集→危险性评价统计模型→泥石流危险区划分→易损性评价→承灾能力评价→泥石流预期损失估算→风险评价为一体的强震区城镇泥石流灾害风险评价方法。论文的主要研究内容包括:(1)基础理论分析。论文在大量国内外研究成果的基础上,对风险的基础理论研究成果进行了系统的归纳和总结,在一般意义风险(危险性和易损性)的基础上,对风险评价的内容进行了补充(融入了承灾能力这一因素);(2)城镇泥石流灾害风险评价的相关理论模式研究。在理论分析的基础上,在对传统风险评价理论方法修正的基础上,系统分析了强震区城镇泥石流灾害风险评价体系,并构建了泥石流灾害风险与危险性、易损性及承灾能力三者的关系耦合模式,同时,还对城镇承灾能力的指标体系和评价方法进行了探讨;(3)强震区城镇泥石流灾害风险评价的技术与方法研究。论文将遥感(RS)和GIS技术相结合,在对强震区泥石流流域特征及承灾体特征进行解译的基础上,应用GIS的空间叠加分析和统计计算等功能,开展了强震区泥石流危险性评价、易损性评价研究。同时,结合典型泥石流沟的实地调查分析,实现了对遥感解译的验证和对承灾能力评价的过程,最终得到泥石流危险性评价图、泥石流易损性评价图及风险评价图;(4)理论方法的应用研究。论文应用所建立的城镇泥石流灾害风险评价方法和体系,以“5.12”汶川大地震强震区之一的汶川县城作为研究对象,通过对威胁到汶川县城城区的南沟和羊岭沟两条泥石流沟进行调查和评价,开展了系统的危险性评价、易损性评价、承灾能力评价、风险计算及风险分区评价研究,对两条泥石流沟在暴发泥石流情况下可能导致的风险进行了分析。通过以上方面的研究,论文主要得到以下研究成果:(1)基本明确了“5.12”汶川大地震强震区泥石流的基本特征。通过对强震区泥石流的形成机制、运动及成灾特征等有了初步的认识,总结出了强震区泥石流灾害的几个典型特征:①强震区泥石流暴发的频率相对震前有增高的趋势,通过对“5.12”汶川大地震前后的降雨资料分析发现,强震区震后暴雨泥石流的临界雨量值相对震前较小,起动的前期累积雨量为震前的14.8%～22.1%,小时雨强约为震前的25.4%～31.6%;②从强震区泥石流的类型有从震前洪水向稀性泥石流转变的特点;③从泥石流产出环境上看,许多震前沟谷泥石流逐渐转变为坡面泥石流+沟谷泥石流的混合型;④从强震区泥石流灾害的规模上看,震后石流的规模是震前同等条件下泥石流规模的数十倍。(2)通过对北川县境内已发生的72条泥石流沟流域地形地貌特征进行统计分析,明确了强震区泥石流流域的基本特征:①与其它地区的泥石流沟相比,强震区泥石流流域面积大小的变幅更广;②流域纵比降主要分布在130～400‰之间,比降变幅范围大;③强震区泥石流沟物源区平均坡度约为33°,与其它地区泥石流流域物源区坡度(25～40°)基本一致;主沟长度多介于1.5～6km范围内,与其它地区泥石流沟的主沟长度(1～10km)相比,整体偏小;④震区内泥石流堆积扇坡度多介于2～10°之间。(3)建立了强震区泥石流冲出距离的评价模型,在此基础上提出了强震区泥石流危险性评价方法。论文在GIS的支持下,对北川县境内的51条暴雨泥石流沟流域特征及泥石流最远冲出距离进行分析,通过将流域高差和堆积区堆积扇顶角及泥石流冲出角之间的统计关系,得到了强震区不同流域面积分类下泥石流最远冲出距离的评价模型。通过模型计算得到的泥石流冲出距离要比实际的冲出距离偏大,从对泥石流进行预测的角度出发,这种评价结果是有实际意义的。(4)在RS和GIS的支持下提出了基于堆积区地形特征的泥石流危险性分区方法。论文在RS和GIS的支持下,根据泥石流流域的地形地貌特征参数,通过建立DEM模型和对可能的堆积区域进行坡度统计和分析,得到了基于堆积区地形坡度和距主沟距离的强震区泥石流危险性分区评价方法。通过将该方法应用于北川已发生的3条泥石流沟,表明用方法来确定泥石流的危险区较为合理。(5)提出了强震区城镇泥石流灾害承灾能力评价的指标体系和评价方法。论文在对承灾体承灾能力影响因素分析的基础上,构建了承灾能力评价指标体系,通过对各个指标的权重计算,得到了承灾能力评价模型,在此基础上,首次将承灾能力这一因素进行赋值量化后融入到风险评价体系中,对完善风险评价理论方法和体系具有理论和实践意义。(6)提出了易损性半定量赋值评价的方法。在RS和GIS的支持下,论文通过遥感解译和实地调查对承灾体进行分类(人口、房屋、生命线设施、农业用地),在对各类承灾体的结构特征与易损性大小之间的关系分析基础上,分别对不同承灾体的结构类型进行赋值,实现了应用RS和GIS技术开展泥石流易损性的半定量化评价研究,对完善泥石流这一学科的研究方法和技术有重要的实践意义。(7)提出了系统的强震区城镇泥石流灾害风险评价方法和体系。论文应用RS(高分辨率遥感影像)和GIS技术,集强震区泥石流灾害风险定义、风险评价内容、评价步骤及评价方法为一体,开展了系统的风险分析、风险计算及风险评价的理论方法和评价体系研究,通过将强震区城镇泥石流灾害风险评价方法和体系应用到汶川县城研究表明,应用高分辨率遥感影像和GIS技术在泥石流风险评价中具有更大的优势,这对完善风险评价的理论和方法具有重要的实践意义。更多还原

【Abstract】 The Richter scale 8.0 earthquake in Wenchuan on 12 May 2008, in Sichuan Provence, southwest of China caused serious casualties and property loss, and caused serious damage to local geologic environment, this not only blocked the reconstruction process in stricken areas, but also give austere challenge to ecologic recovering and the continuable development. There distributed numbers of landslides, collapses, potential unstable slopes in strong seismic zone, these geologic hazards has formed enough moveable materials ,this is benefit to debris flow pregnant. Based on the first step investigation results in earthquake area, there have more than 5 000 geologic hazards distributed in Wenchuan earthquake area. Most of these geologic hazards are landslide, collapse, unstable slope and debris flow. The investigation date of 44 serious damaged countries show, there have more than 872 potential debris flow gullies in this area, among them, 90 debris flow gullies belong to super-huge magnitude, 91 huge magnitude, 300 middle magnitude and 355 little magnitude. The survey result come from Chinese Ministry of Land and Resources show, there are more than 24 country-level cities and 100 towns or villages was endangered by those potential debris flow,On 24, September 2008, only 4 moths after“5.12”Wenchuan earthquake, in the strong damaged areas Wenchuan and Beichuan occurred regional debris flow, caused more 40 people die or missing, thousands acres fertile land and hundreds of houses be buried and damaged, the magnitude and the power of this debris flow was rare, and no debris flow can has equal power to this in other areas. This regional debris flow show that the debris flow in earthquake area has come into a active stage, and the debris flow will be one of the most severe geologic hazards in this area during the future 5 to 10 years. How to carry out the risk assessment and risk control to those potential debris flow is necessary and important, at the same time, this is a prominent problems in reconstruction processing. So to constructing the systematic urban debris flow risk assessment in earth quake area is significant to mitigation plan and reconstruction. Because of the lack of systematic debris flow risk assessment method for earthquake urban, based on the geology theory, geomorphology theory, system science, manage theory and relative theories research progress, based on the date from occurred debris flow investigation and interpretation from high resolution remote sensing image(the resolution is 0.5m), the thesis carried out systematic research of urban debris flow risk assessment method in strong shocked earthquake area. Based on the framework of risk assessment (hazard and vulnerability), added the urban materials bear capability to debris flow factor, to put forward a new debris flow risk assessment framework for urban debris flow. Based on the assessment index construction, use the software of GIS(Arcview), AutoCAD, Matlab to statistics and calculate relative date, carried out risk calculate and assessment, formed a systematic method of earthquake area urban debris flow risk assessment, the processing include: date collect→hazard assessment→hazard subarea→vulnerability assessment→debris flow bear capability assessment→potential loss evaluate→risk assessment. In total, the thesid carried out the relative content study as fellow:(1) Basic theories analysis of risk assessment. Based on numbers of existing relative researchs, we summarized these theories systematicly, promoted and supplemented the risk assessment contents, then, mixed the the urban objict’s sustainability to debris flow into risk assessment framework based on existing risk framework (which comprised of hazard and vulnerability).(2) The study of pattern theory of utban debris flow risk assessment. Based on the relative theory analysis and revise of exiting risk assessment content of debris flow risk assessment, we analyzed the urban debris flow risk assessment method and content, constructed then relationship between risk and hazard, vulnerability and the resist capability of potential suffers, at the same time, we studied the sustainability of urban objicts to debris flow, include the assessment index system and method.(3) The technology and method study of urban debris flow in strong seismic area. By combining the remote sense (RS) and GIS technology and the characters interpretation of debris flow gully and urban objicts in strong seismic area, the thesis carried out spatial analysis, statistic and calculate of debris flow hazard and vulnerability under the GIS sofeware. At the same time, combined the investigation of typical debris flow in strong seismic area to inspect and verify the interpreted result from remote sense image, finally, getting the debris flow hazare map, vulnerability map and risk map.(4) The application of debris flow risk assessment theories.We taking Wenchuan city as an example which is one of the serious effected by“5.12”earthquake to apply the risk assessment theories constructed in the thesis, after the investigation of the two debris flow gully which both are threaten the city, and the potential runout distance calculation of the two debris flow, carried out hazard assessment, vulnerability assessment, the sustanbility of the urban object, risk calculation ande risk subarea study, finally, analyzed the possible debris flow risk and it’s potential danger area.Base on those study, the thesis come to these conclusions.(1)We summarized the basic characters of debris flow in earthquake area. After the analysis of the mechanism and active characters of occurred debris flow, drew many typical characters of debris flow in strong earthquake area:①The frequency of debris flow in earthquake area has the upturn tendency, based on the precipitation date analysis of Beichuan country after the“5.12”Wenchuan earthquake, the critical value of precipitation of debris flow relative lower than before earthquake, after the earthquake, the proceeding accumulate precipitation value before debris flow occur was 14.8～22.1% before earthquake, and the precipitation value of per hour was 25.4～31.6% before earthquake;②From the aspect of debris flow type, the torrent before earthquake has the tendency of convert to low volume weight debris flow after the earthquake, from the aspect of debris flow pregnant environment, many gully-debris flow has the tendency of convert to gully-grade mixed debris flow;③From the magnitude of debris flow, the magnitude after the earthquake is tens times of before earthquake.(2)Based on the topography statistic of occurred 72 debris flow in Beichuan country, we geting the debris flow basin characters:①Compared to another areas, the debris flow basin areas distributing ranges is more wider in strong seismic area;②Compared to another areas, most of the debris flow longitudinal river slope range is more wider, the value are fall between 130～140% in earthquake area,;③The average slope in debris flow initiation area in strong seismic area is 33°, similar to another areas(25～40°), most of debris flow tap drain length are fall between 1.5～6 km, compare to another area debris flow, the value has a little low.④Most of the debris flow alluvial fan slop are fall between 2～10°.(3)The thesis put forward the debris flow run out distance evaluate model, based on this model, building the debris flow hazard assessment method in earthquake area. Sported by the GIS tool, statistic and 51 debris flow run out distance which has occurred on 24 August, 2008, and analysis the basin topography characters, then get the run out distance assessment model.(4)Put forward the method of debris flow hazard subarea assessment, which is based on the topography date of debris flow potential accumulate area slope analysis which draw from the digital elevate model(DEM), then, proposing the debris flow subarea method which is based on the accumulate area slop analysis and the distance from gully. The classify method is: if the accumulate area slope <10°,this match with the high hazard area, the slope fall in 10～15°, match with middle hazard area, the slope fall in 15～20°, match with the low hazard area. As the same method, if the distance from gully <100m, match with high hazard area, the distance fall in 1～200m, match with the middle hazard area, the distance fall in 200～300m, match with the low hazard area. After the application of this method of 3 debris flow in Beichuan country, the result show that this subarea method is feasible.(5)The thesis constructed the index system and assessment method of resist capability to debris flow for earthquake area urban, based on the analysis of the factors which effect the object’s capability of resist to debris flow, constructed the assessment index system, and calculated the weights of each index, then mixed the resist capability to debris flow into risk assessment system, after the classification of capability, give each classified a certain value, and put this value to calculate with hazard and vulnerability assessment result, finally, get the risk assessment results.(6)Put forward the semi-quantitative assessment method based on the index evaluation. Based on the remote sense image interpretation and investigation of study area, classified the objects in urban area (including population, houses, life line facilities, agriculture land), based on the relationship analyze between building type and vulnerability (the different population density and different building type has different vulnerability), evaluate the relative value to different type of objects, then, multiplication these index value to express the vulnerability. Finally, give a semi-quantitative vulnerability assessment result according the criterion of classification.(7)Put forward systematic risk assessment method of strong seismic area urban debris flow, and carried out semi-quantitative risk assessment. The thesis put a integrative study, including the definition of risk, the content of risk assessment, assessment steps and assessment method, carried out systematic risk analyze, risk calculation, and risk assessment. Through the calculation of quantitative evaluated index, put forward the classification criterion of risk, the research has practical significance to complete the risk assessment theories and method.更多还原