局部空间自相关统计洪水灾害影像分析     

王建华  秦其明  杜宸  庞治国  付俊娥  孙越君  郑小坡 《测绘科学》2015,(10):26-29

针对洪水灾害分析在速度、准确性和及时性等方面的需求,该文在研究空间自相关分析的基础上,提出了一种基于局部自相关统计的洪水灾害影像分析方法。首先,对影像进行掩膜处理,去除云层干扰;其次,采用局部空间统计的方法对影像进行统计分析;然后,通过密度分割的方法提取水体,将影像分为水体和陆地两类;最后,将3幅影像分类的结果进行空间叠加分析,分析洪水灾害影响情况。以2013年嫩江流域3个时期的影像为实验数据,设计了仿真实验。实验结果表明,该方法可以较准确地对大面积洪水影响区域进行分析。  相似文献   

Linking past flood frequencies in Norway to regional atmospheric circulation anomalies     

Eivind N. Støren  Erik W. Kolstad  Øyvind Paasche 《第四纪科学杂志》2012,27(1):71-80

Analysis of two continuous, high‐resolution palaeo‐flood records from southern Norway reveals that the frequency of extreme flood events has changed significantly during the Holocene. During the early and middle Holocene, flood frequency was low; by contrast, it was high over the last 2300 years when the mean flood frequency was about 2.5–3.0 per century. The present regional discharge regime is dominated by spring/summer snowmelt, and our results indicate that the changing flood frequency cannot be explained by local conditions associated with the respective catchments of the two lakes, but rather long‐term variations of solid winter precipitation and related snowmelt. Applying available instrumental winter precipitation data and associated sea‐level pressure re‐analysis data as a modern analogue, we document that atmospheric circulation anomalies, significantly different from the North Atlantic Oscillation (NAO), have some potential in explaining the variability of the two different palaeo‐flood records. Centennial‐scale patterns in shifting flood frequency might be indicative of shifts in atmospheric circulation and shed light on palaeo‐pressure variations in the North Atlantic region, in areas not influenced by the NAO. Major shifts are found at about 2300, 1200 and 200 years ago (cal. a BP). Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Flood forecasting and infiltration modeling/Prévision de crue et modélisation de l’infiltration     

《水文科学杂志》2013,58(2)

Abstract

Abstract The role of accuracy in the representation of infiltration on the effectiveness of real-time flood forecasting models was investigated. A simple semi-distributed model of conceptual type with adaptive estimate of hydraulic characteristics included in the infiltration component was selected. Infiltration was described by a very accurate approach recently formulated for complex rainfall patterns, or alternatively through a simpler formulation known as an extension of the classical time compression approximation. The results indicated that, for situations involving a significant rainfall variability in space, the inaccuracy in the representation of infiltration cannot be corrected by the adaptive component of the rainfall–runoff model. A preliminary analysis of the role of an approximation of saturated hydraulic conductivity to be used in each homogeneous area of the semi-distributed model used both in non-adaptive version and in real-time is also presented.  相似文献   

Trend detection in river flow series: 1. Annual maximum flow / Détection de tendance dans des séries de débit fluvial: 1. Débit maximum annuel     

《水文科学杂志》2013,58(5)

Abstract

Results of a study on change detection in hydrological time series of annual maximum river flow are presented. Out of more than a thousand long time series made available by the Global Runoff Data Centre (GRDC) in Koblenz, Germany, a worldwide data set consisting of 195 long series of daily mean flow records was selected, based on such criteria as length of series, currency, lack of gaps and missing values, adequate geographical distribution, and priority to smaller catchments. The analysis of annual maximum flows does not support the hypothesis of ubiquitous growth of high flows. Although 27 cases of strong, statistically significant increase were identified by the Mann-Kendall test, there are 31 decreases as well, and most (137) time series do not show any significant changes (at the 10% level). Caution is advised in interpreting these results as flooding is a complex phenomenon, caused by a number of factors that can be associated with local, regional, and hemispheric climatic processes. Moreover, river flow has strong natural variability and exhibits long-term persistence which can confound the results of trend and significance tests.  相似文献   

On seasonal approach to flood frequency modelling. Part II: flood frequency analysis of Polish rivers     

K. Kochanek  W. G. Strupczewski  E. Bogdanowicz 《水文研究》2012,26(5):717-730

The annual peak flow series of Polish rivers are mixtures of summer and winter flows. As Part II of a sequence of two papers, practical aspects of applicability of seasonal approach to flood frequency analysis (FFA) of Polish rivers are discussed. Taking A Two‐Component Extreme Value (TCEV1) model as an example it was shown in the first part that regardless of estimation method, the seasonal approach can give profit in terms of upper quantile estimation accuracy that rises with the return period of the quantile and is the greatest for no seasonal variation. In this part, an assessment of annual maxima (AM) versus seasonal maxima (SM) approach to FFA was carried out with respect to seasonal and annual peak flow series of 38 Polish gauging stations. First, the assumption of mutual independence of the seasonal maxima has been tested. The smoothness of SM and AM empirical probability distribution functions was analysed and compared. The TCEV1 model with seasonally estimated parameters was found to be not appropriate for most Polish data as it considerably underrates the skewness of AM distributions and upper quantile values as well. Consequently, the discrepancies between the SM and AM estimates of TCEV1 are observed. Taking SM and TCEV1 distribution, the dominating season in AM series was confronted with predominant season for extreme floods. The key argument for presumptive superiority of SM approach that SM samples are more statistically homogeneous than AM samples has not been confirmed by the data. An analysis of fitness to SM and AM of Polish datasets made for seven distributions pointed to Pearson (3) distribution as the best for AM and Summer Maxima, whereas it was impossible to select a single best model for winter samples. In the multi‐model approach to FFA, the tree functions, i.e., Pe(3), CD3 and LN3, should be involved for both SM and AM. As the case study, Warsaw gauge on the Vistula River was selected. While most of AM elements are here from winter season, the prevailing majority of extreme annual floods are the summer maxima. The upper quantile estimates got by means of classical annual and two‐season methods happen to be fairly close; what's more they are nearly equal to the quantiles calculated just for the season of dominating extreme floods. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

A methodology for regional flood frequency estimation based on scaling properties     

Thomas Skaugen  Thomas Vringstad 《水文研究》2005,19(7):1481-1495

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2008年深圳洪涝灾害的气候背景和环流条件   总被引：1，自引：1，他引：1       下载免费PDF全文

王红军  刘文菁  刘培宁  潘维玉 《气象科学》2010,30(2):256-261

用NCC/CMA资料分析了2008年6月深圳降水异常事件的成因,结果认为:2007年7月—2008年2月赤道西太平洋海表温度异常偏低、2008年前冬今春青藏高原积雪面积偏大是深圳异常降水事件的前期气候背景;2008年6月东亚阻塞高压的异常强大及乌拉尔山长波槽的异常加深发展,促进了经向环流异常增强;偏强的冷空气以阶梯槽的形式频繁入侵华南,为深圳异常降水事件提供了动力条件。副高西段较常年偏南,西伸脊点偏东;强劲的季风潮为深圳地区输送了巨大的水汽和热量;冷暖空气在华南地区的频繁交汇与维持是深圳异常降水事件的主要成因。上述多种因素的异常共同导致了深圳异常降水事件的发生。  相似文献   

长江上游全新世特大洪水对西南 季风变化的响应   总被引：1，自引：1，他引：0  

葛兆帅 《地理研究》2009,28(3):592-600

利用24次全新世特大洪水序列与川渝地区近两千年的洪灾史料,对长江上游特大洪水事件和气候变化的响应机制进行了分析。从长江上游特大洪水序列与阿拉伯海记录的西南季风气候变化对比分析来看,特大洪水事件与西南季风变化具有很好的响应关系,特大洪水事件多发生于西南季风较弱的阶段,这些阶段以西南季风气候快速变化为特征,是气候剧烈波动期或气候的转型期。与北大西洋、贵州董歌洞石笋所记录的气候变化比较,特大洪水有的与全新世气候突变一致,有的则不一致,可能特大洪水事件更多表现为地方事件。与文献记载的历史洪灾事件相比,长江上游低频高量级的特大洪水事件对西南季风的变化具有更好的响应关系,而高频低量级的洪灾事件具有更高的随机性,由于历史文献记载的洪水量级差异较大,如果将他们笼统地放在一起分析,可能会掩盖洪水事件对气候变化响应机制。  相似文献   

Dependence of model-based extreme flood estimation on the calibration period: case study of the Kamp River (Austria)     

P. Brigode  E. Paquet  P. Bernardara  J. Gailhard  F. Garavaglia  P. Ribstein 《水文科学杂志》2015,60(7-8):1424-1437

Abstract

The Kamp River is a particularly interesting case study for testing flood frequency estimation methods, since it experienced a major flood in August 2002. Here, the Kamp catchment is studied in order to quantify the influence of such a remarkable flood event on the calibration of a rainfall–runoff model, in particular when it is used in a stochastic simulation method for flood estimation, by performing numerous rainfall–runoff model calibrations (based on split-sample and bootstrap tests). The results confirmed the usefulness of the multi-period and bootstrap testing schemes for identifying the dependence of model performance and flood estimates on the information contained in the calibration period. The August 2002 event appears to play a dominating role for the Kamp River, since the presence or absence of the event within the calibration sub-periods strongly influences the rainfall–runoff model calibration and the extreme flood estimations that are based on the calibrated model.  相似文献   

Terrace aggradation during the 1978 flood on Powder River, Montana, USA     

J.A. Moody  R.H. Meade 《Geomorphology》2008,99(1-4):387-403

Flood processes no longer actively increase the planform area of terraces. Instead, lateral erosion decreases the area. However, infrequent extreme floods continue episodic aggradation of terraces surfaces. We quantify this type of evolution of terraces by an extreme flood in May 1978 on Powder River in southeastern Montana. Within an 89-km study reach of the river, we (1) determine a sediment budget for each geomorphic feature, (2) interpret the stratigraphy of the newly deposited sediment, and (3) discuss the essential role of vegetation in the depositional processes.Peak flood discharge was about 930 m³ s^− 1, which lasted about eight days. During this time, the flood transported 8.2 million tons of sediment into and 4.5 million tons out of the study reach. The masses of sediment transferred between features or eroded from one feature and redeposited on the same feature exceeded the mass transported out of the reach. The flood inundated the floodplain and some of the remnants of two terraces along the river. Lateral erosion decreased the planform area of the lower of the two terraces (~ 2.7 m above the riverbed) by 3.2% and that of the higher terrace (~ 3.5 m above the riverbed) by 4.1%. However, overbank aggradation, on average, raised the lower terrace by 0.16 m and the higher terrace by 0.063 m.Vegetation controlled the type, thickness, and stratigraphy of the aggradation on terrace surfaces. Two characteristic overbank deposits were common: coarsening-upward sequences and lee dunes. Grass caused the deposition of the coarsening-upward sequences, which had 0.02 to 0.07 m of mud at the base, and in some cases, the deposits coarsened upwards to coarse sand on the top. Lee dunes, composed of fine and very fine sand, were deposited in the wake zone downstream from the trees. The characteristic morphology of the dunes can be used to estimate some flood variables such as suspended-sediment particle size, minimum depth, and critical shear velocity. Information about depositional processes during extreme floods is rare, and therefore, the results from this study aid in interpreting the record of terrace stratigraphy along other rivers.  相似文献