城市水文单元雨洪监测与模拟研究——以清华大学校园为例

城市内涝问题进一步突显了城市水文循环研究的重要性。基于地表建筑、地下管道、雨水工程等资料,基于SWMM建立了清华大学校园雨洪模拟模型,根据2015年5月10日和2012年7月21日两场降雨事件的实测资料,进行了清华大学校园水文过程精细模拟,用道路积水深度率定验证模型。模拟结果表明:(1)集水区下垫面透水性强弱不同时,产流过程仍十分相似,最大洪峰发生时间相同;(2)绿化带削减洪量的作用显著,不透水面积越大的地方越容易发生街道积水;(3)道路水深对降雨强度响应敏感,低强度降雨事件中,道路积水表现出0.5~1h的滞后。     

The cold rain‐on‐snow event of June 2013 in the Canadian Rockies — characteristics and diagnosis

The June 2013 flood in the Canadian Rockies featured rain‐on‐snow (ROS) runoff generation at alpine elevations that contributed to the high streamflows observed during the event. Such a mid‐summer ROS event has not been diagnosed in detail, and a diagnosis may help to understand future high discharge‐producing hydrometeorological events in mountainous cold regions. The alpine hydrology of the flood was simulated using a physically based model created with the modular cold regions hydrological modelling platform. The event was distinctive in that, although at first, relatively warm rain fell onto existing snowdrifts inducing ROS melt; the rainfall turned to snowfall as the air mass cooled and so increased snowcover and snowpacks in alpine regions, which then melted rapidly from ground heat fluxes in the latter part of the event. Melt rates of existing snowpacks were substantially lower during the ROS than during the relatively sunny periods preceding and following the event as a result of low wind speeds, cloud cover and cool temperatures. However, at the basin scale, melt volumes increased during the event as a result of increased snowcover from the fresh snowfall and consequent large ground heat contributions to melt energy, causing snowmelt to enhance rainfall–runoff by one fifth. Flow pathways also shifted during the event from relatively slow sub‐surface flow prior to the flood to an even contribution from sub‐surface and fast overland flow during and immediately after the event. This early summer, high precipitation ROS event was distinctive for the impact of decreased solar irradiance in suppressing melt rates, the contribution of ground heat flux to basin scale snowmelt after precipitation turned to snowfall, the transition from slow sub‐surface to fast overland flow runoff as the sub‐surface storage saturated and streamflow volumes that exceeded precipitation. These distinctions show that summer, mountain ROS events should be considered quite distinct from winter ROS and can be important contributors to catastrophic events. Copyright © 2016 John Wiley & Sons, Ltd.     

Urbanization Impact on Regional Climate and Extreme Weather: Current Understanding,Uncertainties, and Future Research Directions

Urban environments lie at the confluence of social,cultural,and economic activities and have unique biophysical characteristics due to continued infrastructure development that generally replaces natural landscapes with built-up structures.The vast majority of studies on urban perturbation of local weather and climate have been centered on the urban heat island(UHI)effect,referring to the higher temperature in cities compared to their natural surroundings.Besides the UHI effect and heat waves,urbanization also impacts atmospheric moisture,wind,boundary layer structure,cloud formation,dispersion of air pollutants,precipitation,and storms.In this review article,we first introduce the datasets and methods used in studying urban areas and their impacts through both observation and modeling and then summarize the scientific insights on the impact of urbanization on various aspects of regional climate and extreme weather based on more than 500 studies.We also highlight the major research gaps and challenges in our understanding of the impacts of urbanization and provide our perspective and recommendations for future research priorities and directions.     

Post‐repair effect of column jackets on aftershock fragilities of damaged RC bridges subjected to successive earthquakes

In light of recent earthquakes, structures damaged during an initial seismic event (mainshock) may be more vulnerable to severe damage and collapse during a subsequent event (aftershock). In this paper, a framework for the development of aftershock fragilities is presented; these aftershock fragilities define the likelihood that a bridge damaged during an initial event will exhibit a given damage state following one or more subsequent events. The framework is capable of (i) quantifying the cumulative damage of unrepaired bridges subjected to mainshock–aftershock sequences (effect of multiple earthquakes) and (ii) evaluating the effectiveness of column repair schemes such as steel and fiber‐reinforced‐polymer jackets (post‐repair effect of jackets). To achieve this aim, the numerical model of repaired columns is validated using existing experimental results. A non‐seismically designed bridge is chosen as a case study and is modeled for three numerical bridge models: a damaged (but unrepaired) bridge model, and two bridge models with columns repaired with steel and fiber‐reinforced polymer jackets. A series of back‐to‐back dynamic analyses under successive earthquakes are performed for each level of existing damage. Using simulated results, failure probabilities of components for multiple limit states are computed for each bridge model and then are used to evaluate the relative vulnerability of components associated with cumulative damage and column repair. Copyright © 2016 John Wiley & Sons, Ltd.     

海岸带城市洪水淹没风险评价研究——以青岛市为例

目前国内海岸带城市洪水淹没风险领域中较多关注单一致灾因子(风暴潮)导致的淹没,缺乏对导致海岸带洪水发生的其他致灾因子的自然属性和社会属性的综合考量。根据风险的内涵,借鉴国外综合性风险评价理念,将洪水淹没自然机理模型与概念框架模型相结合,选取能表征风险发生概率的自然过程指标以及能表征风险危害性后果的社会经济类指标,构建具有针对性的海岸带型洪水淹没风险评价指标体系,对青岛市洪水淹没风险进行综合评估。研究得出青岛市洪水淹没风险指数值为0.3240,根据我国主要海域自然灾害等级划分(表3),可知其风险等级为3,危险性属于中等水平;确定了青岛市洪水淹没风险的各类致灾体与其影响因素之间的相关性;并得出洪水淹没风险的自然因素和人为可控因素两类关键性控制指标制定短期和长期性的适应策略和行动,充分利用可调节因素,有效加强并提高防范性指标,以期到达最大程度上降低青岛市洪水淹没风险。     

地磁低点位移以磁暴倍九法作为补充预测的讨论

短临地震预测方法中,中国地震科学家提出了地磁低点位移法与磁暴倍九法。这两种方法经过了几十年时间的验证,但其对地震进行准确的预测还是较为困难的,鉴于此,建议以低点位移作为第一预测方案的主方案,而以磁暴倍九法作为补充的第二预测方案,以这两方法相配合来预测强地震发生的时间。以此为思路,以期今后能有更多资料与数据来提高此方法在短临预测方面的准确性。     

八宝山煤矿北部正长斑岩岩体的产状及其意义

从岩体的岩性、时代、产状等方面,论证了八宝山煤矿北部的正长斑岩体为一岩盖,下部找煤前景可观,可在井下实施巷探和定向钻探找煤,以延长矿井寿命。     

The seismic signatures of the surge wave from the 2009 Xiaolin landslide‐dam breach in Taiwan

The catastrophic Xiaolin landslide occurred on 9 August 2009, after Typhoon Morakot struck Taiwan. This landslide formed a dam that subsequently breached, burying and flooding the village of Xiaolin. Seismic signals were induced by the landslide and dam breaching and recorded at the Jiaxian broadband seismic station in Taiwan. The time‐frequency spectra for the data from this station were analysed to extract the seismic characteristics of the landslide and to deduce the timing of processes associated with the landslide dam‐break flooding. The duration of the river blockage, the time of the dam breach, the duration of the surge wave and the mean speed of the surge wave were estimated, and the hydrological implications of the flood behaviour were interpreted. The spectral characteristics of the different stream discharges were also studied. Stream water level/discharge is closely related to the frequency of the seismic signals. The broadband stations are particularly useful for flood monitoring due to their ability to continuously record measurements and their high sensitivity. Copyright © 2011 John Wiley & Sons, Ltd.     

Statistical physics of fault patterns self-organized by repeated earthquakes

This work presents at attempt to model brittle ruptures and slips in a continental plate and its spontaneous organization by repeated earthquakes in terms of coarse-grained properties of the mechanical plate. A statistical physics model, which simulates anti-plane shear deformation of a thin plate with inhomogeneous elastic properties, is thus analyzed theoretically and numerically in order to study the spatio-temporal evolution of rupture patterns in response to a constant applied strain rate at its borders, mimicking the effect of neighboring plates. Rupture occurs when the local stress reaches a threshold value. Broken elements are instantaneously healed and retain the original material properties, enabling the occurrence of recurrent earthquakes. Extending previous works (Cowie et al., 1993;Miltenberger et al., 1993), we present a study of the most startling feature of this model which is that ruptures become strongly correlated in space and time leading to the spontaneous development of multifractal structures and gradually accumulate large displacements. The formation of the structures and the temporal variation of rupture activity is due to a complex interplay between the random structure, long-range elastic interactions and the threshold nature of rupture physics. The spontaneous formation of fractal fault structures by repeated earthquakes is mirrored at short times by the spatio-temporal chaotic dynamics of earthquakes, well-described by a Gutenberg-Richter power law. We also show that the fault structures can be understood as pure geometrical objects, namely minimal manifolds, which in two dimensions correspond to the random directed polymer (RDP) problem. This mapping allows us to use the results of many studies on the RDP in the field of statistical physics, where it is an exact result that the minimal random manifolds in 2D systems are self-affine with a roughness exponent 2/3. We also present results pertaining to the influence of the degree of stress release per earthquake on the competition between faults. Our results provide a rigorous framework from which to initiate rationalization of many, reported fractal fault studies.