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1.
A detailed analysis is made of the current ideas concerning floods of a special type. We examine short-lasting torrential flash floods, one of the most widespread and hazardous natural phenomena in the world characterized by a high rate of development, and by a short duration. It is established that such floods are in a primitive stage of study, which is testified by the fact that there is no general consensus as to what should be treated as a flash flood. It is pointed out that a special term designating them is also absent in many countries. It is determined that the key formation conditions for flash floods include intense short-lasting cloudbursts, the occurrence of a river basin in mountainous regions and a small drainage area; on this basis, it is suggested that they be termed flash floods. It is shown that such floods are of the most widespread occurrence in the northern hemisphere in regions with a temperate and subtropical climate. We suggest the scheme of natural factors for formation of flash floods and their differences from debris flows and floods of other types. It is determined that the main problems of investigating the formation mechanisms and forecasting the aforementioned floods are associated with the small spatiotemporal scale of these phenomena.  相似文献   

2.
Bryndal, T. 2015. Local flash floods in Central Europe: A case study of Poland. Norsk Geografisk Tidsskrift–Norwegian Journal of Geography. Vol. 69, 288–298. ISSN 0029-1951.

The article focuses on the seasonality, geographical distribution, and hydrometeorological aspects of local flash floods in Poland, in Central Europe. Scientific articles describing local flash flood events were studied and a database of such floods in Poland was developed and analysed. The results revealed that local flash flood events were usually generated by rainfall lasting less than two hours, with a mean intensity in the range 20–80 mm·h-1. The triggering threshold for local flash floods was P = 20 mm·h-1. Local flash floods may occur from April to October, with higher frequencies in May, June, and July. The floods usually affect mountain and uplands areas differently to lowland and basins regions, and this might be explained by heavy rainfall distribution and topographical conditions. The maxima of the unit discharge (Qs) describe an envelope curve according to the equation Qs = 47A-0.4 (where A is the catchment area in km2). The maxima appear very consistent with envelope curves proposed for other inland continental European countries. The authors conclude that local flash floods in Poland are similar to those recorded in inland continental areas of Europe, but differ from the floods in the Mediterranean part of the continent.  相似文献   

3.
王润  高前兆 《地理科学》1996,16(2):144-149
突发性洪水是干旱区河流重要的水文事件，塔里木河流域突发性洪水主要包括暴雨突发性洪水和冰川湖崩决洪水，本文例举了发生在上游支流的两种类型突发性洪水，对其发生、发展进行了比较分析，同时，分析了不同类型不同支流发生的突发性洪水对干流的影响。  相似文献   

4.
西南地区山洪灾害时空分布特征及其影响因素   总被引：8，自引：1，他引：7  
山洪灾害时空特征和影响因素是山洪评估与管理的重要内容。根据1960-2015年中国西南地区历史山洪资料,采用线性回归、标准差椭圆、空间自相关和Logistic回归模型,深入分析了西南地区山洪灾害时空分布特征及其影响因素。结果表明：① 西南地区年度山洪灾害频次呈指数增长,年际变化呈现出稳定（1960-1980年）、缓慢波动增加（1981-1998年）、快速增加（1999-2015年）3个阶段;月际特征明显,山洪主要发生在每年6-8月,尤以7月频次最高;② 西南地区山洪灾害空间差异性显著,灾害高密度区主要集中于滇中高原地区、四川盆地和周边山地单元,山洪灾害数量分布呈显著的空间正相关,空间集聚特征明显（Moran's I指数为0.127、Z = 5.784、P = 0.007）;③ 西南地区历史灾害点的重心在年内存在明显的向正西方向移动的趋势,年内标准差椭圆转角均逐渐弱化,长轴逐渐变长,短轴逐渐变短;④ 降雨因子对山洪的影响度最高,人类活动因子次之,地表环境因子最低,降雨因子中1 h降雨量对山洪的影响最强,优势比值达到3.654。研究结果可为西南地区山洪灾害形成机理、监测预警研究,实施防灾减灾措施等提供科技支撑。  相似文献   

5.
山洪泥石流风险评估与风险管理理论与方法   总被引：1，自引：1，他引：0  
崔鹏  邹强 《地理科学进展》2016,35(2):137-147
山洪泥石流是中国常见的自然灾害,充分认识其形成机制与潜在风险是防灾减灾的关键。本文阐述了山洪泥石流形成机理,以及风险分析与管理的方法和内容,系统认识了地表产流流量激增、土体破坏物质供给激增、沟道堵塞体级联溃决流量放大和动床侵蚀规模增大等4个山洪泥石流的形成过程,介绍了基于动力过程的山洪泥石流风险评估方法和承灾体易损性评估方法,构建了基于灾害动力过程的风险评估与风险制图方法。进而,基于风险评估结果,提出可用于具体灾害点减灾的风险管理内容和风险调控技术、灾害防治的工程与非工程措施与制技术方案。最后,重点讨论了包括灾害风险预测、临灾预案、灾害防治工程方案等内容的风险处置对策,并形成一套基于山洪泥石流动力过程的风险评估与风险管理理论与方法体系。  相似文献   

6.
Flood inundation is a common natural disaster and a growing development challenge for many cities and thousands of small towns around the world. Soil features have frequently altered with the rapid development of urbanised regions, which has led to more frequent and longer duration of flooding in urban flood-prone regions. Thus, this paper presents a geographic information system (GIS)-based methodology for measuring and visualising the effects on urban flash floods generated by land-use changes over time. The measurement is formulated with a time series in order to perform a dynamic analysis. A catchment mesh is introduced into a hydrological model for reflecting the spatial layouts of infrastructure and structures over different construction periods. The Geelong Waurn Ponds campus of Deakin University is then selected as a case study. Based on GIS simulation and mapping technologies, this research illustrates the evolutionary process of flash floods. The paper then describes flood inundation for different built environments and presents a comparison by quantifying the flooding extents for infrastructure and structures. The results reveal that the GIS-based estimation model can examine urban flash floods in different development phases and identify the change of flooding extents in terms of land-use planning. This study will bring benefits to urban planners in raising awareness of flood impact and the approach proposed here could be used for flood mitigation through future urban planning.  相似文献   

7.
山洪是中国主要的自然灾害之一,严重威胁山区人民生命财产与工程建设安全。针对山洪已发展了多种多样的研究手段,但多集中于过去几十年的时间段内。树轮地貌学方法作为研究历史山洪事件的有效手段之一,在世界范围内被广泛应用。利用树轮中的生长干扰信息,可以对山洪事件进行精确定年,重建无记录或少记录地区内山洪发生的频率、大小和空间分布特征等,根据伤疤的高度或应用水力模型则可以定量重建山洪的流量大小。随着树轮地貌学方法和技术的逐渐成熟,研究趋向于探讨山洪的驱动机制、更大空间尺度山洪的规律性等,具有广阔的应用前景,但是基于树轮的山洪研究工作在国内还未见报道。论文对树轮地貌学应用于山洪研究的发展过程进行了系统回顾,对研究进展进行了简要概述,最后讨论该研究领域的潜力及局限性,以期为在国内进一步开展相关工作提供参考信息。  相似文献   

8.
Hoang Su Phi is a mountainous district in Ha Giang province, Vietnam. When the rainy season arrives in these parts, flash floods (besides landslides), frequently occur in many areas, seriously affecting the socio‐economic condition of the district. Therefore, in this paper, we have developed an early warning system for flash floods, established based on a geomorphological and hydrological approach. The basic principle underlying this system is the fact that flash floods will often occur where there is high potential risk with sufficient rainfall. In the model, eight parameters of the basin were used to build a potential flash flood map. Using the spatial processing module in an open source software, early predictions from automatic weather stations were interpolated and processed online to produce a potential risk map. Depending on the threshold of precipitation values, the results determined locations where flash flood may occur at various flash flood risk indices (FFRI). The system may be applied to support provision of early flash flood warning up to 1?6 days in advance in the district, allowing the local government ample time to make appropriate decisions on the prevention and/or mitigation of damages caused by flash flood hazards.  相似文献   

9.
山洪灾害具有广泛性、突发性、破坏性等特征,开展山洪易发区的社区韧性评估,从而提高灾害应对能力是当前防灾减灾的前沿热点和难点。论文提出了一套多学科的综合方法：(1)利用中介效应明晰了山洪视角下社区韧性评价体系各指标间的定量化传递关系;(2)构建了基于决策实验室分析和解释结构模型的耦合数学模型,确定社区韧性影响因素的多级递阶解释结构模型,分析社区韧性的差异化影响因素;(3)采用信息扩散方法,定量分析山洪灾害社区韧性的变化趋势并排序。以粤北山洪易发区为例,从城镇、村落、城乡结合部3种类型社区进行灾害韧性分析。结果表明：山洪视角下的社区韧性指标体系是一个多维度多层次的复杂网络系统,包括环境、社会、心理、制度和信息沟通5个方面;不同类型社区灾害韧性的直接影响因素呈差异化特征,而供排水设施建设和洪灾应急演练为社区韧性的根本影响因素,对增强山洪视角下社区韧性发挥本质性作用;由于调研村落多位于山洪频发区,居民防范灾害、减轻灾害影响的意识较强,村落较城镇和城乡结合社区呈现出更高的韧性。研究可为提升粤北山洪易发区社区韧性及社区防灾减灾能力提供科学参考,该综合分析方法亦可为其他类型灾害的精细化防灾减灾提供支...  相似文献   

10.
我国干旱区洪水灾害基本特征：以新疆为例   总被引：9，自引：0，他引：9  
依据新疆自然和社会环境,分析了新疆洪水及其洪灾的形成,季节分布,年际变化,地区分布等主要特征,并提出对洪水灾害的防御对策。  相似文献   

11.
The southern part of France near the Mediterranean Sea is subject to flash floods generated by heavy rainfalls typical of the Mediterranean climate. In November 1999 (the 12th and 13th) and in September 2002 (the 8th and 9th), 5000 km2 were touched by rainfalls superior to 200 mm in the departments of Aude and Gard. In both cases, maximum precipitation exceeded 500 mm within 24 h. The damage amounted in the hundreds of millions of euros, and there were numerous fatalities: 35 in 1999, and 23 in 2002. Following a survey of available data, this article details the cost of the damage for both flash flood events. The distribution of the damage is quantified by sector of activity (e.g., industry, agriculture). The average ratio “euros of loss per inhabitant” is quite similar in both cases, but this average hides some geographical discrepancies. Losses in industry can locally worsen the overall toll. The mapping of damage on a local scale and the amount of losses per inhabitant demonstrate that rural areas underwent heavy losses. This was mostly due to the destruction of the public infrastructures (e.g., roads, bridges) that represented more than half of the overall loss. In some rural areas, the cost of flash floods can exceed 15,000 euros per inhabitant. Such flood prevention issues as flood warning systems and land use planning must not focus only on the cities. Death, injury and heavy material losses also disadvantage the rural and mountainous areas where populations and activities are concentrated near rivers.  相似文献   

12.
Journal of Geographical Sciences - Water depths and flow velocities decisively influence the damage caused by flash floods. Geographic Information System (GIS) is a powerful and useful tool,...  相似文献   

13.
暴雨是一种影响力极其严重的灾害性天气之一,连降的暴雨或大暴雨、特大暴雨,常导致山洪爆发,危及人们的生命和财产安全。利用1961~2007年百色12个县(区)的降水实测资料,采用统计分析方法,对百色市暴雨进行分析,得出暴雨时空分布的特征,为该区域暴雨预报起到一定的指导作用。  相似文献   

14.
暴雨山洪灾害预警是中小流域山洪灾害防控体系的薄弱环节,也是决定山洪灾害防控成败的关键。论文围绕山洪灾害预警的核心问题,从中国山洪灾害区域差异特征、山洪灾害预警技术方法、山洪灾害概率预警现状3个方面进行了综述。中国山洪灾害分布存在明显的时空差异,因此有必要根据山洪灾害的区域差异发展有针对性的预警方法。以临界雨量为指标的雨量预警是目前中国中小流域暴雨山洪灾害预警的主要技术手段,但常规方法仅给出一个(组)确定的临界雨量阈值,导致预警结果存在突出的不确定性问题。概率预警可以定量评估诸多不确定性,给出山洪灾害概率预警结果,因此具备很好的理论优势与潜在应用价值。论文展望了山洪灾害概率预警未来的研究重点与方向：(1)充分挖掘暴雨洪水样本信息,开展山洪灾害概率预警基础方法与技术集成研究;(2)加强非平稳性条件下的临界雨量阈值估算与山洪灾害概率预警研究;(3)综合考虑预警阈值发生概率及其致灾概率,优化“多级预警、多级响应”技术方法,推进山洪灾害综合预警业务系统建设与应用。  相似文献   

15.
Schmidt‐hammer exposure‐age dating (SHD) was applied to three flood berms in upper Vetlestølsdalen, southern Norway, using a local, high‐precision calibration curve that takes account of the colluvial origin of fluvial boulders in the youngest berm, which was deposited during the August 1979 flood. Precision of SHD dating for this berm was estimated as ±210 years, whereas predicted ages of the two older berms were 3195 ± 435 and 3405 ± 340 years, and subsections of the oldest berm yielded age ranges of ～900 years. The results demonstrate the feasibility of high‐precision SHD in the context of boulder landforms deposited by high‐magnitude floods, the requirement of a large sample of R values in the face of high natural variability, the necessity of an appropriate calibration curve to ensure accuracy, the usefulness of floods of known age for testing and improving calibration curves, and the potential effects of boulders of colluvial origin on R values (especially the susceptibility of young surfaces to roughness variations). The dated berms indicate a return period of ～1000–1500 years for floods of the magnitude of the 1979 flood event in the upper catchment. Thus, the long‐term persistence of flood boulder berms in the landscape has potential for reconstructing Holocene flood history and palaeohydrology from the geomorphic legacy of the most extreme Holocene floods.  相似文献   

16.
On the basis of cartographic materials and the theory of atmospheric electricity, the concept of forest flash fires in the Far East is suggested. A statistical correlation between the onset time of disastrous natural phenomena (floods, droughts) and the time of impulse of the zonal atmospheric circulation is demonstrated.  相似文献   

17.
Rivers in drylands typically are characterized by extreme flow variability, with long periods of little or no flow interspersed with occasional large, sometimes extreme, floods. Complete adjustment of river form and process is sometimes inhibited, resulting in a common assumption that equilibrium conditions may rarely, if ever, exist in dryland rivers, and that transient and unstable (nonequilibrium) behavior is the norm. Examples from the Channel Country and the Northern Plains in central Australia challenge that notion. Along the middle reaches of these intermediate and large, low-gradient rivers, where long duration floods generate moderate to low unit stream powers and boundary resistance is high as a result of indurated alluvial terraces, cohesive muds or riparian vegetation, there is evidence that: (1) channels have remained essentially stable despite large floods; (2) sediment transport discontinuities, while present at a catchment scale, are largely insignificant for channel form and process in individual reaches; (3) there are strong correlations between many channel form and process variables; and (4) many rivers appear to be adjusted to maximum sediment transport efficiency under conditions of low gradient, abundant within-channel vegetation and declining downstream discharge. In these middle reaches, rivers are characterized by equilibrium conditions. However, in the aggradational lower reaches of rivers on the Northern Plains, where upstream terraces are buried by younger sediments and channels are less confined, nonequilibrium conditions prevail. Here, channels sometimes undergo sudden and substantial changes in form during large floods, sediment transport discontinuities are readily apparent, and landforms such as splays remain out-of-balance with normal flows. Hence, dryland rivers can exhibit both equilibrium and nonequilibrium conditions, depending on factors such as catchment size, channel gradient, flood duration, unit stream power, channel confinement, sediment cohesion, and bank strength. [Key words: dryland rivers, floods, equilibrium, nonequilibrium, central Australia.]  相似文献   

18.
High sediment delivery due to catchment and channel erosion can impact on waterway health and reservoir sedimentation. Methods that decrease sediment connectivity within the system are needed to address these potential impacts. Vegetation has the potential to decrease channel erosion and sediment transfers in dryland environments by increasing channel bed resistance and roughness. Detailed studies of vegetation and process interactions were undertaken within an ephemeral channel in SE Spain at three scales (channel network, reach and patch) by repeat surveys and mapping after floods. Connectivity mapping showed variations in vegetation type and density along the channel and that these influence sediment retention and channel erosion. Hydraulic calculations of vegetation roughness effects at 25 cross-sections down the channel indicate the influence of different vegetation type and characteristics. Particular attention was paid to the perennial grass Lygeum spartum because of its potential benefits in channel stabilisation. Sedimentation takes place within these reaches, mainly by trapping within and downstream of individual plants. Check dams have a profound influence on vegetation and sediment distribution in this channel but use of vegetated zones may be a more sustainable strategy of sediment control.  相似文献   

19.
River islands are defined as discrete areas of woodland vegetation surrounded by either water‐filled channels or exposed gravel. They exhibit some stability and are not submerged during bank‐full flows. The aim of the study is to analyze the dynamics of established, building, and pioneer islands in a 30‐km‐long reach of the gravel‐bed Piave River, which has suffered from intense and multiple human impacts. Plan‐form changes of river features since 1960 were analyzed using aerial photographs, and a LiDAR was used to derive the maximum, minimum and mean elevation of island surfaces, and maximum and mean height of their vegetation. The results suggest that established islands lie at a higher elevation than building and pioneer islands, and have a thicker layer of fine sediments deposited on their surface after big floods. After the exceptional flood in 1966 (RI > 200 years) there was a moderate increase in island numbers and extension, followed by a further increase from 1991, due to a succession of flood events in 1993 and 2002 with RI > 10 years, as well as a change in the human management relating to the control of gravel‐mining activities. The narrowing trend (1960–1999) of the morphological plan form certainly enhanced the chance of islands becoming established and this explains the reduction of the active channel, the increase in established islands and reduction of pioneer islands.  相似文献   

20.
Through the alteration of the physical characteristics of a landscape, such as the destruction of vegetation and the formation of a hydrophobic layer, a fire can dramatically amplify erosion rates. On the basis of field observations, it has been proposed that the deposition of a layer of ash on the ground surface can enhance the erosion of mountainous terrain by surface runoff and might even be a necessary condition for the generation of progressively bulked debris flows. In this study, a flume was constructed to investigate the role of ash in increasing both the volume and the transport capacity of runoff. The experiments demonstrated that the presence of ash on the soil surface reduces the ability of flowing water to infiltrate; this effect is even greater when the ash has been pre-wetted. In addition, the ability of ash slurries to infiltrate decreases with increasing ash concentration. The results also indicate that the transport capacity of runoff is enhanced by the incorporation of ash into the flow because of the increased fluid density. However, the addition of ash reduces the boundary Reynolds number such that, at high ash concentrations and with fine-grained sediment, sediment transport declines as the flow becomes hydraulically smooth. The experimental results were also used to evaluate the ability of steep flow fronts, a common characteristic of debris flows and flash floods, to increase sediment transport rates. Finally, it is proposed that ash slurries may evolve into progressively bulked debris flows through a positive feedback between fluid density, transport capacity, and erosivity.  相似文献   

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