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1.
This paper presents the results of a pilot study for assessing debris-flow hazards using geographic information system (GIS) techniques. The watershed of the Chen-Yu-Lan River is investigated in this pilot study. Factors that are believed to be critical to the occurrence of debris flow are identified and considered in the assessment of debris-flow hazards. Using the spatial analysis feature of GIS, the impact of these factors, expressed in terms of debris-flow hazard (DH) index, is calculated. By taking a simple summation of all DH indexes according to each factor, the overall debris-flow hazard at a particular watershed may be assessed. The applicability of the proposed approach for analyzing the watershed of the Chen-Yu-Lan River has been confirmed with the field observations in a recent typhoon event. 相似文献
2.
2008年“5·12”汶川地震极大地改变了震区泥石流的特征,不仅增强了泥石流的活动性,同时也使得震区在相当长的时间内都要面临泥石流的威胁。本文基于前人大量的研究成果,并利用遥感解译结合现场调查等手段,分析了汶川县泥石流沟道纵坡降、沟壑密度、两岸坡度等基本发育特征;进而分析了地震前后汶川县降雨分布及泥石流相关降雨参数变化特征。结果显示,流域内泥石流沟的沟壑密度在0.2~4之间,属于微度土壤侵蚀区域,泥石流的沟床纵坡降偏大,有利于泥石流的发生;泥石流流域内斜坡坡度多为30°~40°,有利于灾害的发生;震后汶川县年均降雨量增加了5.17%,降雨多集中在7~9月份,降雨量由南及北逐渐降低;震后泥石流的降雨阈值在2008~2013年呈现缓慢回升的趋势,但2019年又有所下降,预计恢复到震前水平尚需要一定时间;同时震后汶川县泥石流物源丰富,震后物源量呈现“震荡式衰减”的演化趋势,但体量仍然很大,对泥石流仍需坚持监测预警工作。 相似文献
3.
Debris flows often occur in the mountainous watersheds of earthquake-affected areas, and in the Lushan earthquake area of southwestern China, they have become a significant hazard. In this study, the influencing factors and spatial distribution of debris flows were analyzed through a review of their occurrence history. Debris flows are mainly distributed in the northwestern part of the study area, which hosts the greatest density of active faults. The debris flows are generally formed by the ‘progressive bulking’ effect in channels, and deep incision, lateral erosion, and blockage breaking are common processes that amplify the magnitude of such debris flows. Rainfall thresholds for different types of debris flow were proposed to explain the spatial differences between debris-flow regions, and the temporal variations of those thresholds highlighted how the rainfall conditions required for the occurrence of debris flows have changed. Natural vegetation recovery, reduction in the availability of solid material, and artificial debris-flow control projects play important roles in raising the threshold of the rainfall conditions required for triggering debris flows. 相似文献
4.
A channelized debris flow/flood generally originates from initial gully erosion by superficial runoff that evolves rapidly into massive erosion of the channel bed. Knowledge of the formation conditions of such events is crucial for accurate forecasting, and determination of rainfall and runoff thresholds for such hazards is a primary concern following a strong earthquake. This work proposed a framework for debris flow/flood formation at the watershed scale in two watersheds (area: 2.4 and 32.4 km2) in the Wenchuan Earthquake area (China). The critical runoff and rainfall conditions required for debris flow/flood formation were simulated and their annual variations investigated. Ultimately, the runoff conditions required for debris flow/flood formation in the two studied watersheds were calculated on an annual basis and found to increase in time. Similarly, following consideration of three different rainfall types, critical rainfall conditions were proposed that also showed an increasing tendency. The increase of rainfall and runoff conditions for debris flow/flood formation is attributable to both the recovery of vegetation and the reduction of source materials. In comparison with actual monitored flow behaviors and previously proposed rainfall thresholds, the results showed strong consistency and high forecasting efficiency. 相似文献
5.
切沟侵蚀不仅破坏土地资源，而且影响下游地区环境。目前的土壤侵蚀预报模型没有包括切沟侵蚀，因此研究切沟中土壤水分空间变化是建立切沟侵蚀模型的基础，也是恢复植被的基础。在陕西省安塞大南沟流域选择一个切沟，从1998-2000年连续 3年在 4～10月间对切沟不同部位土壤水分状况进行了观测。分析结果表明，切沟中浅层土壤水分空间分异规律明显，沟顶土壤水分状况较好，土壤容积湿度达到10．3％。沟坡则较差，但沿沟坡向下到沟底，土壤水分不断增加，分别为 6．3％、6．4％和10．4％。沟坡陡崖的土壤水分条件最差，接近凋萎湿度，容积含水量仅为4.6％～5.9％。沟底土壤湿度有所好转，为 7．7％。从雨季开始到结束，整体上土壤水分呈下降趋势，但随降雨事件发生波动。季节变化比较明显的是土壤水分条件好的部位，如沟顶、沟坡底部和沟底。尤以沟底变化最大。沟坡陡崖土壤湿度随季节没有任何变化。从1998-2000年，随降水量减少，切沟所有部位土壤湿度持续下降，即使在水分条件较好的沟顶和沟坡下部，土壤湿度也仅为 8．1％～8．8％，其它部位则都接近于凋萎湿度。土壤水分亏缺相当严重。切沟不同部位土壤水分的季节和年际变化主要受降雨入渗补给影响，而沟底则与径流的产生有关。因此应进一步研究不同降雨类型与径流产生、以及土壤湿度变化的关系。 相似文献
6.
【 研究目的】泥石流灾害是白龙江流域分布广泛并常引起群死群伤的重大地质灾害,准确评价泥石流活动规模及其危险度,是泥石流危险性预警预报的前提,合理构建危险性预报模型是泥石流防灾减灾的关键。【 研究方法】本文以研究区历史泥石流案例和对应降雨资料为基础数据,采用统计分析方法,通过分析形成泥石流关键地质环境条件及其相互关系,构建了白龙江流域潜在泥石流危险度定量评价模型,提出了两类泥石流危险级别临界判别模式。【 研究结果】结果表明：（1）以泥石流活动规模、沟床平均比降、流域切割密度、不稳定沟床比例为判断因子的泥石流危险度动态定量计算模型,能快速准确预测未来不同工程情景和降雨频率工况下泥石流危险度;（2）影响降雨型泥石流发生的地形条件由流域面积、10°~40°斜坡坡度面积比、沟床平均纵比降等组成,降雨条件主要由泥石流爆发前的24 h累积降雨量、触发泥石流1 h降雨量或10 min降雨量等组成;（3）依据30条典型泥石流沟危险度计算结果,获得泥石流危险性临界判别值,提出了降雨型潜在泥石流危险性1 h预报模型（Ⅰ类）和10 min预报模型（Ⅱ类）,其中Ⅰ类模型高危险度以上泥石流预测精度大于87.5%,Ⅱ类模型中等危险度以上泥石流预测精度大于80%,而两类预报模型验证准确率为83.3%。【 结论】研究成果为泥石流精准预警预报提供了技术支撑,对建立中小尺度泥石流实时化预警系统具有一定参考意义。 创新点：通过确定与泥石流相对应关键地质环境因子,构建了泥石流危险度动态定量评价模型,依据泥石流危险性1 h和10 min临界判别模式可准确实现潜在泥石流预警预报。 相似文献
7.
Debris flows frequently occurred in Wenchuan earthquake region from 2008 to 2010, resulting in great damage to localities and being a prolonged threat to reconstruction. Forty three events' data including debris-flow volume, sediment volume and watershed area are analyzed and compared with other debris-flow events in Eastern Italian Alps, burned areas in USA and in Taiwan. The analysis reveals that there is a strong empirical relationship between debris-flow volume and loose materials volume in the earthquake region. In addition, the relationship between debris-flow volume and watershed area in the earthquake region has a wider variation range than that in other three regions while the debris volume also appears to be larger than that in the other three regions, which implies the volume of debris flows with strong influence of earthquakes is larger than that with no such influence and it is hard to predict the post-quake volume only by the watershed area. The comparison of the maximal debris-flow erosion modulus in the Wenchuan region and in Taiwan indicates that debris flows will be very active in a short time after strong earthquake. 相似文献
8.
Several giant debris flows occurred in southwestern China after the Wenchuan earthquake, causing serious casualties and economic losses. Debris flows were frequently triggered after the earthquake. A relatively accurate prediction of these post-seismic debris flows can help to reduce the consequent damages. Existing debris flow prediction is almost based on the study of the relationship between post-earthquake debris flows and rainfall. The relationship between the occurrence of post-seismic debris flows and characteristic rainfall patterns was studied in this paper. Fourteen rainfall events related to debris flows that occurred in four watersheds in the Wenchuan earthquake area were collected. By analyzing the rainfall data, characteristics of rainfall events that triggered debris flows after the earthquake were obtained. Both the critical maximum rainfall intensity and average rainfall intensity increased with the time. To describe the critical conditions for debris flow initiation, intensity–duration curves were constructed, which shows how the threshold for triggering debris flows increased each year. The time that the critical rainfall intensities of debris flow occurrences return to the value prior to the earthquake could not be estimated due to the absent rainfall data before the earthquake. Rainfall-triggering response patterns could be distinguished for rainfall-induced debris flows. The critical rainfall patterns related to debris flows could be divided on the basis of antecedent rainfall duration and intensity into three categories: (1) a rapid triggering response pattern, (2) an intermediate triggering response pattern, and (3) a slow triggering response pattern. The triggering response patterns are closely related to the initiation mechanisms of post-earthquake debris flows. The main difference in initiation mechanisms and difference in triggering patterns by rainfall is regulated by the infiltration process and determined by a number of parameters, such as hydro-mechanical soil characteristics, the thickness of the soil, and the slope gradient. In case of a rapid triggering response rainfall pattern, the hydraulic conductivity and initial moisture content are the main impact factors. Runoff erosion and rapid loading of solid material is the dominant process. In case of a rainfall pattern with a slow triggering response, the thickness and strength of the soil, high hydraulic conductivity, and rainfall intensity are the impact factors. Probably slope failure is the most dominant process initiating debris flows. In case of an intermediate triggering response pattern, both debris flow initiation mechanisms (runoff erosion and slope failure) can play a role. 相似文献
9.
国内对泥石流治理措施谷坊坝、格栅坝的作用和效果研究较多,而对滑坡型泥石流的综合治理措施和效果研究较少。2010.8.14强降雨过程导致汶川震区映秀镇烧房沟滑坡型泥石流暴发,通过分析其运动过程和现状沟道特征,结合滑坡堵点和沟道深切的特点,治理工程采用防堵防切综合工程结构形式:上游谷防群+中游抗滑桩、挡土板和肋板护脚护底+下游3座格栅坝+渡槽明洞跨越G213,并分析各分项工程作用:减弱龙头动能+控制LS01堵点、保护鞋尖+拦粗放细、顺畅排导。最后利用2010.8.14与2013.7.10的历史降雨量和固体参与量对比、工程治理前后动储量对比和各分项工程治理前后的沟道特点对比,验证了烧房沟滑坡型泥石流综合治理工程的效果良好。为今后震区滑坡型泥石流工程防治提供参考。 相似文献
10.
An extended probabilistic model that is a modification of the Chen et al. (2007,) model for evaluating the failure probability
of an inclined soil layer with an infinite length was developed in the present paper, and then applied to evaluate the occurrence
probability of landslide-related debris flow in Tungmen gully located in the eastern Taiwan, which occurred a devastating
debris flow in 1990. The statistical properties of hydrogeological parameters were collected and summarized, and then used
to evaluate the landslide-related debris-flow probabilities at various relative water depths for Tungmen gully by using the
probabilistic model. Under the assumption that the soil is saturated, the soil’s cohesion is negligible and the specific gravity
of the solid particles of soils is a constant, a simplified probabilistic critical slope equation for the stability of an
infinite slope of soils was also developed, and used to estimate the occurrence probability of debris flow. The result shows
that probabilistic landslide analysis for an infinite slope could provide a suitable approximation for the risk analysis of
debris flow mobilization at a given gully. 相似文献
11.
以四川九寨沟地区牙扎沟泥石流为研究对象,通过数次野外调查及历史资料的统计,详细研究该泥石流的暴发特点、临界雨量及暴发成因,在成因模式分析的基础上提出相应的防治方案。研究结果表明:泥石流具有隐蔽性、突发性、破坏性和输沙能力较强的暴发特点;汶川地震后泥石流暴发的临界雨量仅为2008年“5·12”汶川地震前的一半,2014年至今流域未发生泥石流,临界雨量有逐渐恢复的趋势;短历时强降雨、深切拉槽式物源补给和高陡的地貌条件是泥石流暴发的根本原因;泥石流的成因模式为“降雨渗流、岩土饱水、山洪冲击、沟道深切拉槽、溯源侵蚀、冲刷淘蚀、岸坡侧蚀坍塌、悬移滚动”。这种震后 “拉槽”式泥石流治理应在提高设防标准和优化治理结构形式的同时,以控制集中区物源启动为主、拦挡为辅的防治思路为指导。研究结果可为该地区类似泥石流的防治及预警提供借鉴。 相似文献
12.
赵家沟位于北川县擂鼓镇坪上村西北侧,属汶川地震极重灾区,在地震发生前为一般性清水沟或洪水沟。由于地震的影响,流域内发育了多处滑坡和崩塌,斜坡上和沟道中堆积了大量松散固体物质。在2008年9月24日暴雨的作用下,赵家沟流域发生了百年不遇的泥石流灾害,成为地震次生泥石流沟。通过现场实地调查和室内分析,对地震次生泥石流灾害形成的地质地貌条件、物源条件和水源条件进行了分析。表明地震次生泥石流灾害的发生频率和规模有可能加大,其危险性由于松散固体物质的增大而上升,这是地震次生泥石流灾害显著的特征。 相似文献
13.
A rainfall-induced debris flow warning is implemented employing real-time rain gauge data. The pre-warning for the time of landslide triggering derives the threshold or critical rainfall from historical events involving regional rainfall patterns and geological conditions. In cases of debris flow, the time taken cumulative runoff, to yield abundant water for debris triggering, is an important index that needs monitoring. In gathered historical cases, rainfall time history data from the nearest rain gauge stations to debris-flow sites connected to debris flow are used to define relationships between the rainfall intensity and duration. The effects by which the regional rainfall patterns (antecedent rainfall, duration, intensity, cumulative rainfall) and geological settings combine together to trigger a debris-flow are analyzed for real-time monitoring. The analyses focused on 61 historical hazard events with the timing of debris flow initiation and rainfall duration to burst debris-flow characteristics recorded. A combination of averaged rainfall intensity and duration is a more practical index for debris-flow monitoring than critical or threshold rainfall intensity. Because, the outburst timing of debris flows correlates closely to the peak hourly rainfall and the forecasting of peak hourly rainfall reached in a meteorological event could be a valuable index for real-time debris-flow warning. 相似文献
14.
文家沟位于绵竹市清平乡,属于5·12汶川Ms8.0级地震极重灾区.地震发生后的3个汛期内,文家沟曾先后发生5次典型泥石流灾害,其中以2010年8月13日泥石流灾害最为严重,规模与灾情巨大,社会影响深远.在对文家沟泥石流跟踪调查的基础上,探讨了泥石流的成灾机理和特征.研究表明:(1)文家沟泥石流是地震和强降雨共同作用的结... 相似文献
15.
利用搜集的汶川震区典型泥石流暴发前后的降雨过程资料,分析了泥石流的激发雨量过程,获得了汶川震区的泥石流激发雨量特征,以期为泥石流的预测预报提供依据。结果表明,汶川地震区的泥石流激发雨型可分为快速激发型、中速激发型和慢速激发型3类,其差异主要体现在降雨的持续时间和强度方面。不同激发雨型下的泥石流形成过程的差别主要体现在松散土体饱和过程。雨型的差异(降雨的持续时间和强度)使得土体饱和产生超渗产流的时间出现差异,进而使得泥石流暴发的时间存在差异。激发雨强跟激发雨型存在一定的关系,激发雨强最大者为中速激发雨型,其次是慢速激发雨型,最小者为快速激发雨型。与地震之前相比,地震后的泥石流暴发时的累积雨量和临界雨量都有所降低。 相似文献
16.
Debris flows are more frequent in central Taiwan, because of its mountainous geography. For example, many debris flows were
induced by Typhoon Herb in 1996. The Chi-Chi earthquake with a magnitude of 7.3, which took place in 1999 in central Taiwan,
induced many landslides in this region. Some landslides turned into debris flows when Typhoon Toraji struck Taiwan in 2001.
This study investigates the characteristics of the gullies where debris flows have occurred for a comparison. Aerial photos
of these regions dated in 1997 (before the earthquake) and 2001 (after the earthquake) are used to identify the occurrence
of gully-type debris flows. A Geographic Information System (GIS) is applied to acquire hydrological and geomorphic characteristics:
stream gradient, stream length, catchment gradient, catchment area, form factor, and geology unit of these gullies. These
characteristics in different study regions are presented in a statistical approach. The study of how strong ground motion
affects the debris flows occurrence is conducted. The characteristics of the debris flow gullies triggered by typhoons before
and after the Chi-Chi earthquake are quantitatively compared. The analysis results show that a significant transformation
in the characteristics was induced by the Chi-Chi earthquake. In general, the transformation points out a lower hydrological
and geomorphic threshold to trigger debris flows after the Chi-Chi earthquake. The susceptibility of rock units to strong
ground motion is also examined. The analysis of debris flow density and accumulated rainfall in regions of different ground
motion also reveal that the rainfall threshold decreases after the Chi-Chi earthquake. 相似文献
17.
为进一步探明银洞子沟物源区坡面物源启动机理与降雨的相关性,在进行详细的现场考察与工程勘察工作后选取了典型模型体,并采用20余组人工降雨物理试验方法将降雨强度与坡度设为控制变量,研究了4种坡形、5种雨强条件下,坡面松散物源的失稳机制及破坏模式。试验结果揭示了地表变形与地下物理力学参数变化的定量响应关系,并基于试验发生破坏的临界雨量,建立了银洞子沟传统I-D预警模型。之后提炼可靠预警参数(坡度、深部体积含水率),通过数学回归分析方法并采用Exponential模型,得出IGD、IGM多参数新型预警判别式,实现了传统I-D模型的有效修正,并具一定的可靠性和实用价值。 相似文献
18.
为了探究不同雨型条件下泥石流流量变化特征,通过搜集汶川震区典型泥石流降雨数据,将其概化为三次峰值早到型、三次峰值型、三次峰值晚到型三种雨型。以HEC-HMS水文模型构建高家沟流域模型,在获得流域清水流量结果基础上采用雨洪修正法计算不同雨型下泥石流流量。结果表明三次峰值早到型、三次峰值型、三次峰值晚到型峰值清水流量分别为33.5,41.5,45.8 m3/s,泥石流峰值流量分别为166.83,206.67,228.08 m3/s,误差为-25.6%、-7.8%、1.7%;三种雨型下流量从上游至沟口以线性方式演变,且随降雨峰值推迟其演变速率不断增大,而增长幅度逐渐减小;泥石流暴发出现在峰值降雨前后,属于降雨激发型泥石流;三种雨型随降雨峰值推迟,流量增长阶段所需时间越长,分别为5.5,6,9 h,而衰退阶段所需时间越短,分别为14.5,8,2.5 h。研究表明该模型能为缺少降雨监测数据地区泥石流研究提供技术支持。 相似文献
19.
A combination of empirical and physically based hydrological models has been used to analyze historical data on rainfall and debris-flow occurrence in western Campania, to examine the correlation between rainfall and debris-flow events. Rainfall data from major storms recorded in recent decades in western Campania were compiled, including daily series from several rain gauges located inside landslide areas, supplemented by hourly rainfall data from some of the principal storms. A two-phase approach is proposed. During phase 1, soil moisture levels have been modelled as the hydrological balance between precipitation and evapotranspiration, on a daily scale, using the method of Thornthwaite [Geograph. Rev. 38 (1948) 55]. Phase 2 is related to the accumulation of surplus moisture from intense rainfall, leading to the development of positive pore pressures. These interactions take place on an hourly time scale by the “leaky barrel” (LB) model described by Wilson and Wiezoreck [Env. Eng. Geoscience, 1 (1995) 11]. In combination with hourly rainfall records, the LB model has been used to compare hydrological effects of different storms. The critical level of retained rain water has been fixed by the timing of debris-flow activity, related to recorded storm events. New rainfall intensity–duration thresholds for debris-flow initiation in western Campania are proposed. These thresholds are related to individual rain gauge and assume a previously satisfied field capacity condition. The new thresholds are somewhat higher than those plotted by previous authors, but are thought to be more accurate and thus need less conservatism. 相似文献
20.
2012年8月18日四川省彭州市龙门山镇地区遭受50年一遇的暴雨,引发大规模群发性泥石流灾害,其中以高架子沟最为突出,导致银厂沟内居民生活和交通严重受损。本文据现场调查和航空影像解译,分析高架子沟流域、物源特征的基础上讨论该次泥石流的演化过程、启动方式及灾害机理。结果表明：高架子沟在震前是一条非泥石流沟,震后流域内物源丰富,泥石流形成及演化过程为：地震-滑坡、崩塌-降雨-泥石流,其成灾启动过程包括启动阶段、加速阶段、下切拉槽阶段、堆积四个阶段,启动模式为沟床启动型。该泥石流形成过程中,＂消防水管效应＂使沟道水流快速集中,并强烈冲刷沟床中的松散堆积体,导致沟床固体物质移动形成大规模的泥石流灾害。 相似文献
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