基于灰色关联法的地震灾区泥石流危险性评价以北川县泥石流为例

汶川地震后,地震灾区泥石流具有暴发临界雨量小,规模大,危险性高的特点。在考虑降雨和地震作用下,采用灰色关联法分析北川县72条泥石流沟的泥石流规模、流域面积、主沟长度、流域相对高差、流域切割密度、不稳定沟床比、年均降雨量和地震烈度8个影响因子的权重,在此基础上建立震区泥石流危险性评价模型并进一步对其进行危险性评价。结果表明:影响因子中,年均降雨量和地震烈度所占权重最大; 运用本文模型得到的评价结果与刘希林模型基本一致,但危险度值相对提高,其中有7条泥石流沟危险度提高一个等级。     

基于理想点法的武都区北山泥石流危险度评价

武都区北山泥石流灾害发育,对城区安全构成严重威胁。本文选取泥石流规模及发生频率作为主要因子,沟谷流域面积、主沟长度、流域相对高差、流域切割密度、泥沙补给长度比作为次要因子,采用理想点法对武都区北山7条泥石流沟进行了危险度评价。评价结果表明:研究区泥石流沟属低度危险-中度危险,与单沟泥石流危险度评价方法的结论基本吻合,符合实际情况,验证了该方法具有合理性及可靠性,为泥石流危险度评价提供了一种新的思路,同时也为研究区泥石流灾害的防治提供了科学依据和参考。     

四川都江堰龙溪河流域泥石流成因、特征和危险性评价

在汶川地震影响下,截至2011年龙溪河流域共计有45条泥石流沟暴发泥石流,造成重大经济财产损失.在龙溪河流域泥石流灾害野外调查的基础上,对形成泥石流的地形、降水、物源成因进行了研究,认为物源和降水是激发龙溪河流域泥石流的主要原因.龙溪河流域泥石流具有群发性和小流域暴发性特征,构造带耦合特征,破坏性大和灾害链作用特征.采用MFCAM模型对龙溪河流域泥石流沟进行危险性评价,结果显示有1条沟危险性大,14条危险性中等,30条危险性小.     

四川都江堰龙溪河流域泥石流成因、特征和危险性评价

在汶川地震影响下，截至2011年龙溪河流域共计有45条泥石流沟暴发泥石流，造成重大经济财产损失.在龙溪河流域泥石流灾害野外调查的基础上，对形成泥石流的地形、降水、物源成因进行了研究，认为物源和降水是激发龙溪河流域泥石流的主要原因.龙溪河流域泥石流具有群发性和小流域暴发性特征，构造带耦合特征，破坏性大和灾害链作用特征.采用MFCAM模型对龙溪河流域泥石流沟进行危险性评价，结果显示有1条沟危险性大，14条危险性中等，30条危险性小.     

基于GIS的震后汶川潜在泥石流危险性评价

汶川8级地震造成当地极大的生命和财产损失,震后次生地质灾害又给灾区规划重建带来严重影响.本文分析了汶川震后滑坡、崩塌等地质灾害的时空分布特征,以流域为单元,选用改进后的震后泥石流总流量计算公式,以泥石流物源总量与沟床比降为评价因子,建立单沟泥石流危险性评价模型,对57条潜在泥石流沟进行了危险性评价.实地调查及相关资料验证表明,评价结果与实际较为吻合,具有较强实用性,可为汶川灾后重建规划与地质灾害防治提供技术支持.     

“8·3”鲁甸地震背景下甘沟流域泥石流危险性评价

2014年8月云南省鲁甸县发生6.5级地震,位于震源中心地带的甘沟流域受地震影响,诱发大量次生地质灾害,流域内松散堆积物质增加,泥石流灾害的潜在危险增大,对沟口集镇造成威胁。本文基于对甘沟流域野外实地调查,综合考虑降雨对震后泥石流的影响,选取泥石流规模、流域面积、日最大降雨量、主沟长度、相对高差、流域切割密度、不稳定沟床比等7个评价因子,通过调整分辨系数为0.227 2的灰色关联法确定其客观权重,并在此基础上采用多因素综合评价方法计算泥石流危险度,对其进行危险性定量评价。结果表明,震后甘沟流域泥石流危险性属中度危险,诱发中等规模泥石流的可能性较大。     

汶川震区典型泥石流动态演变特征研究——以绵竹市走马岭泥石流为例

汶川地震后,流域内产生大量松散物源,使走马岭沟由一季节性冲沟演变为一条潜在泥石流沟,在地震后的3个汛期内发生多次泥石流,并造成灾害,其中以2008-9-24泥石流和2010-8-13泥石流最为严重。本文利用3期遥感影像并结合野外调查,对走马岭沟泥石流的形成条件进行了论述,对比分析了走马岭泥石流沟2008年、2009年、2010年3个汛期后流域的动态变化特征,主要表现为:(1)在不同降雨强度下,走马岭泥石流具有复合型物源区启动方式,并先从局部性支沟发生泥石流,进而演变为整个流域全面暴发泥石流。(2)经历了2008年、2009年、2010年3个雨季后,走马岭流域物源储量及物源供给形式发生变化,其中崩塌规模增加了1.87%; 滑坡增加了25.35%; 沟道及坡面松散堆积减少了67.47%,减少部分大部分转化为泥石流沟道堆积物。(3)不同降雨强度下,走马岭泥石流堆积区范围边界变化明显,且不同堆积扇间存在叠加关系; 结合走马岭"9·24"堆积扇范围和"8·13"堆积扇前缘堆积痕迹及影像特征,推测出走马岭"8·13"堆积扇堆积面积约8.76×104m2。最后对泥石流成因机理及发展趋势进行了初步分析。结果显示,走马岭为一高频泥石流沟,仍具备形成大规模泥石流的条件。     

安宁河流域典型沟谷泥石流危险性评价

冕宁县安宁河流域为地质灾害密集分布区,安宁河断裂穿越于此,构造复杂,冷渍沟在上游左岸发育。在强降雨条件下,该沟就会暴发泥石流,堵塞安宁河流域和掩埋杀叶马村房屋和道路。冷渍沟泥石流具有流域面积小,主沟长度短,沟床纵比降大等特征,为了研究安宁河流域内泥石流的危险性,以冷渍沟为例,分析不同降雨周期下的泥石流暴发强度,模拟泥石流的运动过程并进行危险性评价。模拟的最大流速、最大堆积深度和降雨强度三者结合建立冷渍沟泥石流危险性评价模型。研究结果表明,冷渍沟泥石流危险范围内高危险区域占27%,主要集中在松散固体物质较多的沟道,中危险性区域和低危险区域各占56%和17%,该结论为危险范围内的居民和重点设施的风险管控提供参考。     

基于小流域的地震扰动区降雨型滑坡泥石流危险性评价方法

地震扰动区存在大量震裂松散坡体,在持续或者密集的降雨条件下极易转化为滑坡灾害。同时,滑坡又会给泥石流提供大量松散固体物质,增加泥石流的危险性。因此,在震区,灾害通常以"链"的形式出现,比单一灾种危害性大。为了更有效地对地质灾害危险性进行评价,笔者将滑坡、泥石流作为灾害链,综合地加以分析和研究。选择5·12汶川大地震中受灾严重的都江堰市白沙河流域的17条泥石流沟作为研究区,建立滑坡-泥石流危险性评价耦合模型,研究24 h不同降雨量条件下小流域滑坡泥石流危险性的变化。耦合模型包括了坡体稳定性评价模型,水文模型及以泥石流规模、发生频率、流域面积、主沟长度、流域高差、切割密度、不稳定斜坡比为评价因子的泥石流危险性评价统计模型。研究结果表明:随着降雨量的增大,参与泥石流活动的松散物质方量持续增加,但当24 h降雨量超过200 mm后,泥石流沟的危险度等级不再发生变化;17条泥石流沟中4条为中危险度,12条为高危险度,1条为极高危险度。这说明研究区地质灾害问题相当严峻,在多雨季节存在泥石流群发的可能性,直接威胁到居住在泥石流沟附近的人民群众生命财产安全;因此,对于有直接危害对象的高危险度及其以上的泥石流沟,应该按照高等级设防标准进行工程治理及发布预警报。同时也说明,将滑坡、泥石流作为灾害链研究具必要性和可行性。     

基于不同评价单元和灾害熵的泥石流危险性分析

白龙江流域为泥石流等地质灾害密集分布区。2020年8月由于强降雨激发,白龙江流域武都段发生了大规模的群发性泥石流灾害,造成严重损失。文章以白龙江流域甘肃省陇南市武都段（宕昌县两河口乡—武都区桔柑镇）为研究区,通过野外实地考察,选取流域面积、流域形状系数、平均坡度、沟谷密度、物源参照值（HI）、岩性、流域中心距活动断层距离、一小时最大降雨量、植被覆盖度作为泥石流危险性评价因子。基于灾害熵理论,分别以泥石流单沟和小流域单元作为评价单元,利用ArcGIS软件,进行区域泥石流危险性评价。分析结果表明,研究区内泥石流沟大多数都属于中、高危险性。致灾因子中岩性、物源参照值（HI）、距断层距离、植被覆盖度及平均坡度的权重最大,与实际考察结果一致。且以小流域单元作为评价单元的评价结果更符合研究区的泥石流发育情况。     

Effect assessment of debris flow mitigation works based on numerical simulation by using Kanako 2D

Mitigation works are very essential for mitigation of debris-flow hazards in mountainous areas. Usually, it is difficult to assess the effectiveness of existing mitigation works in a catchment. This paper presented a method for quantitative assessment of debris flow mitigation measures by using Kanako system, a user-friendly GUI-equipped debris flow simulator that allows good visualization and easy interpretation. Kanako 2D (Ver. 2.04) was applied to a case study at Caijia Gully, Sichuan Province, China. Mitigation works including check dams, drainage channel, and deposition basin were constructed in the gully in 2001 and 2006. Kanako 2D can simulate debris flow from steep area to alluvial fan. 1D simulation was applied for assessing the effect of the check dams at the lower part of the gully, and 2D simulation was applied for the effect of the drainage channel and deposition basin on the alluvial fan. The simulation results indicate that debris flow will cause great damage to residential area on the alluvial fan if mitigation measures were not implemented in the gully. For old dams which have been filled up with deposits of previous debris flows, the results show that they still have the function for controlling debris flow due to the gradient reduction of the channel bed in front of the dams by the trapped debris flow deposition. After the comprehensive control of debris flow including trapping, drainage, and deposition in the gully, the simulation results indicate that the risk on the alluvial fan can be reduced to an acceptable level.     

Assessment of Debris-Flow Hazards of Alluvial Fans

A strategy is presented for the assessment ofdebris-flow hazards on alluvial fans on the basis ofa case study carried out on the southern foot of astratovolcano named Mt. Yatsugatake. Transformation ofcommercial forests into a golf course was planned ata corner of the Kikkakezawa fan. The case studyinvolves an assessment of hazards due to debris flowsof different magnitudes and their recurrenceintervals. The environmental conditions for therecurrence of these debris flows are discussed as wellas the extent of the areas affected by them. In orderto generalize the case study, concepts of hazardpotential, hazard and risk for debris flows onalluvial fans are established. Accordingly, the hazardpotential is the possible hazards at any location onan alluvial fan in an indefinitely long time period,which can be assessed on the basis of hydrological andother geoscientific investigations. Hazards associatedwith a particular land use can be evaluated on thebasis of the hazard potential considering the locationand the time period associated with the land use. Riskcan be further assessed considering the life styles inthis land and the social conditions.     

城市泥石流风险评价探讨

探讨了城市泥石流风险评价的系统方法,该方法包括泥石流扇形地危险区划、城市易损性分析和城市泥石流风险评价三个主要内容。泥石流堆积扇危险区划是基于数值模拟计算出的泥深和流速分布图进行叠合完成的。以美国高分辨率的“快鸟”卫星影像为数据源,完成了研究区的城市土地覆盖类型遥感解译,在此基础上完成了城市泥石流易损性分析,应用地理信息系统提供的统计和分析工具,完成了研究区泥石流风险评价。该风险区划图可用于指导对泥石流易泛区的不同风险地带的土地利用进行规划和决策,从而达到规避和减轻灾害的目的,也为生活在泥石流危险区的城市居民提供有关灾害风险信息,以作避难和灾害防治的依据。     

砾质辫状河型冲积扇沉积微相及沉积模式:以准噶尔盆地西北缘现代白杨河冲积扇为例*

冲积扇砂砾岩储集层具有相变快、连续性差等特点,显示冲积扇内部沉积环境的复杂性。本次研究以准噶尔盆地西北缘现代白杨河冲积扇为例,在丰富的野外露头资料基础上,结合区域水文资料以及冲积扇文献资料,对白杨河冲积扇沉积演化特征及沉积模式进行探讨。按其沉积机制,白杨河冲积扇属于辫状河型冲积扇,具有规模大(扇体总面积约327.6km²)、坡度平缓(约4‰~7‰)、沉积粒度粗和漫洪细粒沉积物不发育的典型特征。在白杨河冲积扇内共可识别出16种岩相类型,并根据岩相形成的流体动力差异划归为5类成因,即重力流成因、高流态牵引流成因、低流态牵引流成因、静水沉积成因以及风成沉积成因。白杨河冲积扇扇体建造过程可划分为洪水期和间洪期2个时期,洪水期以沉积作用为主,从扇根至扇缘依次发育扇根补给水道沉积、扇根片流沉积、扇中片流沉积、扇中辫状水道沉积、扇缘径流水道沉积和扇缘湿地沉积6种沉积微相类型;间洪期以改造作用为主,从扇根至扇缘依次发育扇根主槽沉积、扇中辫状沟槽沉积和扇缘湿地沉积3种沉积微相类型。最后,依据白杨河冲积扇建立了砾质辫状河型冲积扇洪水期和间洪期的沉积模式。     

Prediction of the run-out distance of the debris flow based on the velocity attenuation coefficient

Our aim is to determine the run-out distance of the debris flow that is crucial in the assessment, prevention and control of the debris flow hazard. Based on the variation characteristic of debris flow velocity in the alluvial fan, this paper proposes the calculation method of the velocity attenuation coefficient of the debris flow. By defining the velocity attenuation coefficient and deducing its calculating formula, this paper puts forward a new method to determine the run-out distance of the debris flow based on the velocity attenuation coefficient, and Gangou debris flow in Luding County, Sichuan Province is selected as a case for calculation and verification. Having 10 m as its measuring spacing, this paper measured 19 sections at the alluvial fan of the Gangou debris flow (among them, 11 sets of data are valid). And based on the measurement, this paper analyzes the characteristic of the velocity attenuation and calculates its velocity attenuation coefficient after the 2005 debris flow. The study indicates that when the velocity of Gangou debris flow at the alluvial fan is greater than 12 % of the initial velocity (at the mouth of gully), the attenuation is quite remarkable. But when the velocity at the alluvial fan is less than 12 % of the initial velocity, the attenuation is quite slow. Besides, when Gangou debris flow rushes out of the gully mouth (the initial velocity is 10 m/s) and when it attenuates to the 32 time, its velocity is less than 0.1 m/s, the debris flow is considered to stop flowing, and the run-out distance of Gangou debris flow is calculated to be 320 m. But the present alluvial fan of Gangou debris flow is measured to be 285 m in length, and the calculated run-out distance is 320 m, which is 35 m longer than its present length. This means when the debris flow runs out in 2005, it blocked up the main river (Dadu River) in some extent. And this finding is generally in accordance with that from the field survey. The findings can be of theoretical and practical significance in the debris flow hazard assessment, as well as its prevention and mitigation.     

Hazard assessment of debris flows in the Wenchuan earthquake-stricken area,South West China

The Longxi river basin with the city of Dujiangyan, in the Sichuan province of South West China, belongs to the seismic area of the May 12, 2008 Wenchuan earthquake. Lots of loose co-seismic materials were present on the slopes, which in later years served as source material for rainfall-induced debris flows. A total of 12 debris flows, were triggered by heavy rainfall on August 13, 2010 in the study area. The FLO-2D numerical analysis software was adopted to simulate debris flows intensity, including movement velocities and maximum flow depths. A comparison of the measured fan spreading with the simulation results, the evaluation parameter Ω was used to verify accuracy of simulation, the results show Ω values ranging between 1.37 and 1.65 indicating relative good simulation results. This study also estimated the flood hydrograph for various recurrence intervals (20, 100, and 200 years, respectively) to perform scenario simulations of debris flows, and followed Swiss and Austrian standards to establish a debris flow hazard classification model on the basis of a combination of the debris flow intensity and the recurrence period. This study distinguishes three hazard classes: low, medium, and high. This proposed approach generated a debris flow hazard distribution map that could be used for disaster prevention in the Wenchuan earthquake-stricken area, South West China.     

南方山地丘陵区典型地质灾害成因机制与风险评价

南方山地丘陵区地域跨度大,地质灾害孕灾背景复杂、成灾模式多样,是我国地质灾害高易发区。针对南方山地丘陵区地质灾害潜在风险高的问题,在中国地质调查局“南方山地丘陵区地质灾害调查工程”实施进展基础上,对南方山地丘陵区地质灾害控灾的气候动力特征及地质构造背景进行了系统分析,对典型地质灾害成灾模式和多尺度风险调查评价示范性成果进行了总结,揭示了东南沿海地区典型台风地质灾害、南方岩溶塌陷、西南高寒山区冰碛土泥石流及川西高原区火后泥石流形成机理与物源侵蚀机制。在此基础上,开展了南方山地丘陵区基于县域、重点城镇及典型灾害点的多尺度地质灾害风险评价应用示范,相关成果在西南重大工程规划选线及县城搬迁选址中得到应用。     

汶川地震后四川省绵竹市清平乡文家沟泥石流灾害调查研究

在2008年5月12日汶川地震后的地震灾区暴发了许多泥石流灾害,其中以四川省绵竹市清平乡文家沟泥石流最为显著。文家沟原来不是泥石流沟,在汶川地震时由于滑坡形成的巨大的滑坡-碎屑流堆积体改变了文家沟的泥石流形成条件,在此后的3个雨季内,文家沟先后暴发了5次大规模和特大规模的泥石流灾害,其中以8.13文家沟泥石流规模和危害最大。8.13文家沟泥石流暴发时的总降雨量为227mm,泥石流持续时间约2.5h,泥石流总量约310×104m3;泥石流造成7人死亡,5人失踪,39人受伤,479户农房被掩埋,直接经济损失4.3亿元。5次大规模和特大规模的泥石流以及洪水仅带走了16%的可以很容易形成泥石流的滑坡-碎屑流堆积物,文家沟如再遭遇较大降雨还会暴发泥石流。即使在今后的雨季中暴发几次规模如8.13泥石流一样大的特大规模泥石流,文家沟在较大降雨下仍然可能暴发泥石流灾害,因此对文家沟泥石流的防治工作将是一个长期的工作。