城市群地震

城市群是我国经济快速发展的产物,已有的震例表明其震害比单个城市的震害更为复杂、严重,对社会的影响更为巨大。分析了城市群的地震灾害特点、我国已有城市群的地震活动性以及相应的防震减灾对策。     

Linking urban water balance and energy balance models to analyse urban design options

Using a water balance modelling framework, this paper analyses the effects of urban design on the water balance, with a focus on evapotranspiration and storm water. First, two quite different urban water balance models are compared: Aquacycle which has been calibrated for a suburban catchment in Canberra, Australia, and the single‐source urban evapotranspiration‐interception scheme (SUES), an energy‐based approach with a biophysically advanced representation of interception and evapotranspiration. A fair agreement between the two modelled estimates of evapotranspiration was significantly improved by allowing the vegetation cover (leaf area index, LAI) to vary seasonally, demonstrating the potential of SUES to quantify the links between water sensitive urban design and microclimates and the advantage of comparing the two modelling approaches. The comparison also revealed where improvements to SUES are needed, chiefly through improved estimates of vegetation cover dynamics as input to SUES, and more rigorous parameterization of the surface resistance equations using local‐scale suburban flux measurements. Second, Aquacycle is used to identify the impact of an array of water sensitive urban design features on the water balance terms. This analysis confirms the potential to passively control urban microclimate by suburban design features that maximize evapotranspiration, such as vegetated roofs. The subsequent effects on daily maximum air temperatures are estimated using an atmospheric boundary layer budget. Potential energy savings of about 2% in summer cooling are estimated from this analysis. This is a clear ‘return on investment’ of using water to maintain urban greenspace, whether as parks distributed throughout an urban area or individual gardens or vegetated roofs. Copyright © 2007 John Wiley & Sons, Ltd.     

城市地下管线探测研究进展与发展趋势

地下管线是城市基础设施的重要组成部分,是保障城市运行和发展的"生命线".但由于建设规模不够、资料保存缺失、日常管理不足等原因,对于地下管线的精准探测变得愈加困难.为此,本文对国内外关于地下管线探测的文献进行了系统调研,详细梳理了常见地下管线的分类、材质、规格以及敷设方式,分析了不同管线的地球物理特征,并重点介绍了当前应用于管线探测的主流地球物理方法(如电磁感应法、探地雷达法等)和非地球物理方法(如惯性陀螺仪定位法、声学探测法等)的应用原理、发展概况、探测优势与应用局限.总结得知,无论是单一探测法,还是综合探测法,都取得了不错的应用效果.其中,利用电磁感应法探测金属管线优势明显、效果显著,包括追踪小口径电力、通讯电缆都能保证较高的精度.而探地雷达则是当前探测非金属管线的首选工具.两种方法互为补充,是地下管线探测应用最普遍的技术,但其抗干扰能力和仪器的探测精度仍有待进一步提高.同时惯性陀螺仪定位法、声学探测法等非地球物理方法也在近些年逐渐得到应用和推广,对主流的地球物理方法做了很好的补充.随着科技不断发展,地下管线探测技术与3S、信息网络、数字测绘等技术联合应用,建立健全集成统一的地下管线信息系统将是未来发展的必然趋势.     

Assessing uncertainties in urban drainage models

The current state of knowledge regarding uncertainties in urban drainage models is poor. This is in part due to the lack of clarity in the way model uncertainty analyses are conducted and how the results are presented and used. There is a need for a common terminology and a conceptual framework for describing and estimating uncertainties in urban drainage models. Practical tools for the assessment of model uncertainties for a range of urban drainage models are also required to be developed. This paper, produced by the International Working Group on Data and Models, which works under the IWA/IAHR Joint Committee on Urban Drainage, is a contribution to the development of a harmonised framework for defining and assessing uncertainties in the field of urban drainage modelling. The sources of uncertainties in urban drainage models and their links are initially mapped out. This is followed by an evaluation of each source, including a discussion of its definition and an evaluation of methods that could be used to assess its overall importance. Finally, an approach for a Global Assessment of Modelling Uncertainties (GAMU) is proposed, which presents a new framework for mapping and quantifying sources of uncertainty in urban drainage models.     

城市交通系统抗震可靠性研究

本文通过对城市交通系统各组成单元可靠性的研究,从系统网络全局出发,以单元可靠度作为控制参数,对交通系统网络的可靠性进行研究。文中指出了震后救护队的最佳选址以及需要改建、加固的路段等,从而为震前交通系统的防灾规划提供理论依据。     

城市地震压埋人员分布评估研究——以天津市区为例

地震压埋人员分布是震后科学、有效地开展应急处置和救援的重要依据。针对地震中建筑物破坏造成的人员压埋,从人口分布和在室率着手,在社区级空间尺度上分时段建立人口数量、在室率和建筑物的对应关系;结合建筑物震害评估方法,构建地震压埋人员快速评估模型,并预评估天津市区各烈度下地震压埋人口的数量和分布情况。结果显示,夜间是发生地震压埋的高风险时段,住宅、大学、居民服务类和卫生医疗建筑是地震压埋高发区域,工作日白天应重点关注中小学。     

Site response effects on an urban overpass

Strong ground motion variability due to rapid changes in subsoil conditions may lead to different site responses, which in turn yields to beneficial or detrimental soil–foundation–structure interaction. This technical note presents the results of a seismic soil–structure interaction analysis conducted using a 2D finite difference model, developed with the program FLAC, of a critical section of a 60 km long strategic urban overpass, which is under construction in Mexico City, for a M_w 8.7 earthquake. Initially, the response of the free field was calibrated comparing the values obtained with FLAC, with those gathered using the computer code QUAD4M. Good agreement was observed between the results generated with these programs. Accelerations and displacements were determined at the upper deck and foundation of the urban overpass. Important seismic soil–structure interaction was observed along the overpass at the supports analyzed. This numerical study helps to gain insight regarding the site response ground motion incoherence effects that influence the dynamic behavior of this kind of structures during extreme events.     

Seismic response evaluation of an urban overpass

The seismic response of one section of a 23 km strategic urban overpass to be built in the so‐called transition and hill zones in Mexico City is presented. The subsoil conditions at these zones typically consist on soft to stiff clay and medium to dense sand deposits, randomly interbedded by loose sand lenses, and underlain by rock formations that may outcrop in some areas. Several critical supports of this overpass are going to be instrumented with accelerometers, inclinometers and extensometers, tell tales and end pile cell pressures to assess their seismic performance during future earthquakes and to generate a database to calibrate soil–structure interaction numerical models. This paper presents the seismic performance evaluation of the critical supports located in one section of the overpass. Sets of finite elements models of the soil–foundation–structure systems were developed. Initially, the model was calibrated analyzing the seismic response that an instrumented bridge support exhibited during the June 15th, 1999 Tehuacan (M_w = 7) Earthquake. This bridge is located also within the surroundings of Mexico City, but in the lake zone, where highly compressible clays are found. The computed response was compared with the measured response in the free field, pile‐box foundation and bridge deck. Once the model prediction capabilities were established, the seismic response of the critical supports of the urban overpass was evaluated for the design earthquake in terms of transfer functions and displacement time histories. Copyright © 2010 John Wiley & Sons, Ltd.     

Enhanced modeling of latent heat flux from urban surfaces in the Noah/single-layer urban canopy coupled model

The numerical modeling of the impacts of urban buildings in mesoscale meteorological models has gradually improved in recent years. Correctly representing the latent heat flux from urban surfaces is a key issue in urban land-atmosphere coupling studies but is a common weakness in current urban canopy models. Using the surface energy balance data at a height of 140 m from a 325 m meteorological tower in Beijing, we conducted a 1-year continuous off-line simulation by using a coupled land surface model and a single-layer urban canopy model and found that this model has a relatively large systematic error for simulated latent heat flux. To improve the numerical method for modeling latent heat flux from urban surfaces, we combined observational analysis and urban land surface model to derive an oasis effect coefficient for urban green areas; to develop a temporal variation formula for water availability in urban impervious surfaces; and to specify a diurnal profile and the maximum values of anthropogenic latent heat release for four seasons. These results are directly incorporated into the urban land surface model to improve model performance. In addition, this method serves as a reference for studies in other urban areas.     

Pervious and impervious runoff in urban catchments

Abstract

Rainfall and runoff depths were examined for 763 storms on 26 urban basins located in 12 countries. For 17 of the basins, impervious surfaces were the major contributors to storm runoff. These basins were generally smaller than 25 ha and had small to medium storms in the data set. Nine basins had significant amounts of runoff from pervious as well as impervious surfaces. Eight of these basins are located in Australia. For all 26 basins, plots of rainfall and runoff depths were used to estimate the effective impervious area and the impervious area initial loss. The data plotted close to a single straight line on all basins, indicating that the effective impervious area remained constant for all storm sizes. The effective impervious fraction was related to total impervious area and the directly connected impervious fraction estimated from maps. For the basins with pervious runoff, the depth of rain in the storm was the most important factor in determining pervious runoff for rainfalls less than 50 mm, while for larger storms other factors including rainfall intensity and antecedent wetness were also found to be significant.     

Assessment of groundwater inflow in urban territories

Analytical and numerical methods are proposed for the calculation of water inflow into construction pits under various geological—engineering and hydrogeological conditions at the construction site. Water inflow into the pit is shown to depend not only on lateral seepage but also on the leakage from underlying aquifers at appropriate parameters of their interaction. Under certain natural conditions, the most efficient method for construction pit draining at low water yield of soils in the construction area are light wellpoint systems, the capacity and layout of which is determined by the potential inflow through the pit contour. The results of analytical and numerical calculations for the assessment of groundwater inflow into a pit are given, and light wellpoint systems are shown to be effective under different combinations of natural and engineering conditions.     

The metastability of natural and urban aerosols

Summary The principle of the sampling method of submicron aerosols with the Aerosol Spectrometer is briefly described and the analytic procedures for deriving the frequency-size distributionC _d (d) from photo-micrographic particle counts and microphotometric light scattering measurementsS _d (d) of identical areas of the particle deposit.After initial analysis the deposits were exposed to elevated temperature (80° C) for several hours and re-analyzed. Four representative aerosol types, originating from the high sea, the shore, vegetation, and metropolitan smog are analyzed in this manner for the range (0.2 d1.3 ). All show a very marked decrease, even disappearance of the smaller particles (d<0.5 ) and shrinkage of the larger particles (d<1 ). By far the largest effect is observed for the smog aerosols.This volatility appears to be caused by either evaporation of the particle substace or by the gradual oxidation of its organic components into more volatile products (CO₂, H₂O).     

Hydrologic processes at the urban residential scale

In the face of increasing urbanization, there is growing interest in application of microscale hydrologic solutions to minimize storm runoff and conserve water at the source. In this study, a physically based numerical model was developed to understand hydrologic processes better at the urban residential scale and the interaction of these processes among different best management practices (BMPs). This model simulates hydrologic processes using an hourly interval for over a full year or for specific storm events. The model was applied to treatment and control single‐family residential parcels in Los Angeles, California. Data collected from the control and treatment sites over 2 years were used to calibrate and validate the model. Annual storm runoff to the street was eliminated by 97% with installation of rain gutters, a driveway interceptor, and lawn retention basin. Evaluated individually, the driveway interceptor was the most effective BMP for storm runoff reduction (65%), followed by the rain gutter installation (28%), and lawn converted to retention basin (12%). An 11 m³ cistern did not substantially reduce runoff, but provided 9% of annual landscape irrigation demand. Simulated landscape irrigation water use was reduced 53% by increasing irrigation system efficiency, and adjusting application rates monthly based on plant water demand. The model showed that infiltration and surface runoff processes were particularly sensitive to the soil's physical properties and its effective depth. Replacing the existing loam soil with clay soil increased annual runoff discharge to the street by 63% when climate and landscape features remained unchanged. Copyright © 2006 John Wiley & Sons, Ltd.     

Seismic reliability assessment of urban water networks

We present a framework for the seismic risk assessment of water supply networks, operating in either normal or abnormal conditions. We propose a methodology for assessing the reliability of water pipe networks combining data of past non‐seismic damage and the vulnerability of the network components against seismic loading. Historical data are obtained using records of damages that occur on a daily basis throughout the network and are processed to produce‘survival curves’, depicting their estimated survival rate over time. The fragility of the network components is assessed using the approach suggested in the American Lifelines Alliance guidelines. The network reliability is assessed using graph theory, whereas the system network reliability is calculated using Monte Carlo simulation. The methodology proposed is demonstrated both on a simple, small‐scale, network and also on a real‐scale district metered area from the water network of the city of Limassol, Cyprus. The proposed approach allows the estimation of the probability that the network fails to provide the desired level of service and allows the prioritization of retrofit interventions and of capacity‐upgrade actions pertaining to existing water pipe networks. Copyright © 2013 John Wiley & Sons, Ltd.     

Intra-annual variability of urban effects on streamflow

While considerable research has established the impacts of urbanization on streamflow, there has been little emphasis on how intra-annual variations in streamflow can deepen the understanding of hydrological processes in urban watersheds. This study fills this critical research gap by examining, at the monthly scale, correlations between land-cover and streamflow, differences in streamflow metrics between urban and rural watersheds, and the potential for the inflow and infiltration (I&I) of extraneous water into sewers to reduce streamflow. We use data from 90 watersheds in the Atlanta, GA region over the 2013–2019 period to accomplish our objectives. Similar to other urban areas in temperate climates, Atlanta has a soil-water surplus in winter and a soil-water deficit in summer. Our results show urban watersheds have less streamflow seasonality than do rural watersheds. Compared to rural watersheds, urban watersheds have a much larger frequency of high-flow days during July–October. This is caused by increased impervious cover decreasing the importance of antecedent soil moisture in producing runoff. Urban watersheds have lower baseflows than rural watersheds during December–April but have baseflows equal to or larger than baseflows in rural watersheds during July–October. Intra-annual variations in effluent data from wastewater treatment plants provide evidence that I&I is a major cause of the relatively low baseflows during December–April. The relatively high baseflows in urban watersheds during July–October are likely caused by reduced evapotranspiration and the inflow of municipal water. The above seasonal aspects of urban effects on streamflow should be applicable to most urban watersheds with temperate climates.     

城区河流中沉水植物分布特征及其影响因素分析——以宁波城区内河为例

以宁波城区内河为研究对象,调研沉水植物在154条河中的分布情况,实测63个代表样点的水环境指标,分析秋、冬季沉水植物群落变化及生理变化.研究发现：宁波城区内仅有8条河流单一地生长有沉水植物轮叶黑藻（Hydrilla verticillata）、苦草（Vallisneria natans）和金鱼藻（Ceratophyllum demersum）中的1种;3种沉水植物分布与溶解氧、氧化还原电位和pH均呈显著正相关,与水深、氨氮（NH₃-N）和总磷（TP）浓度均呈显著负相关;有沉水植物分布的河道水深较浅（约0.9 m）、水质更优（普遍优于V类）;与秋季相比,冬季3种植物的群落盖度均下降,轮叶黑藻和苦草体内丙二醛、过氧化氢含量升高,暗示植物细胞受损;而3种沉水植物均具有一定耐低温胁迫能力,主要表现为体内抗氧化酶活性、可溶性蛋白和可溶性糖含量升高.结果表明,水深、NH₃-N、TP、溶解氧以及低温可能会影响城区内河沉水植物的生长与分布.     

城市地震应急指挥决策支持软件数据库的建立

设计了城市地震应急指挥决策支持软件数据库的原型,介绍了数据库和软件功能模块的关系,给出了该数据库应包括的内容,设计了数据库中空间数据和属性数据的结构及数据类结构,并介绍了数据来源以及数据的处理方法和过程。对城市建立地震应急指挥决策支持软件有参考价值。     

基于GIS技术的城市地震应急能力研究

研究以绵阳市为例,选取城市人口密度、固定应急避难场所服务区范围、派出所服务区范围、医院服务区范围、消防队服务区范围及重大危险源爆炸范围等6项基本因子,利用GIS技术和层次分析法（AHP）对城市地震灾后应急能力进行研究。得到的绵阳市地震灾后应急能力主要结论有2个。（1）处于中低灾害应对能力的区域占总研究区面积的60.28%,表明:绵阳市二环路内整体灾害应急能力偏低,防灾减灾风险较大。（2）灾后应急能力较弱的地区主要为园艺山片区、南河片区、小枧片区以及二环路东西沿线。研究成果可为绵阳市制定城市专项防灾规划提供指导和建议,研究分析方法亦可为国内其他城市的防灾研究提供借鉴。     

改进TOPSIS模型在城市地震脆弱性评估中的应用

针对目前仅以城市单体为对象研究城市地震灾害脆弱性,而忽视城市内部不同区域间存在特征差异的问题,选择威海市区作为研究对象,将研究范围细化至22个街道(镇),建立城市小区域地震灾害脆弱性评价模型。从人口、经济、建筑物和生命线系统4个方面选取17个指标构建城市地震脆弱性评价指标体系,应用主客观结合的三角模糊熵法和改进TOPSIS模型,计算出研究区域的相对贴近程度并进行排序,将威海市区划分为4个不同脆弱性等级。结果表明:改进TOPSIS模型能够从整体上对城市地震灾害脆弱性进行评级分区,为城市内部有针对性的制定防震减灾策略提供一个全新的思路。     

Assessing urban low-carbon performance from a metabolic perspective

How to mitigate anthropogenic carbon emissions in cities determines to a large degree whether global temperature targets in this century are to be met. Using 12 cities in or outside China as case studies, we quantified the critical processes of carbon metabolism based on the urban carbon metabolism assessment framework(CMAF) proposed. The differences of sector contribution, and per capita and intensity among carbon throughflows, carbon inflows and carbon emissions were evaluated.Furthermore, we established an indicator system for CMAF consisting of flow-based and structural indicators to compare the low-carbon performances of cities. The results showed that the total carbon throughflow(TCT) and total carbon inflow(TCI) in Chinese cities were 7–12% higher than in European and American cities regarding the manufacturing and services sector on average, but 6–9% lower in the household consumption sector. Beijing, Tianjin, Nanjing and Guangzhou had lower per capita TCT and TCI than in European and American cities such as Paris and Los Angeles, while their carbon intensities were about three times as much. The per capita TCT in a city was found significantly correlated with per capita energy consumption and had a certain correlation with per capita building or housing area. This study found that TCT, TCI and carbon dioxide emission each provided unique information to measure the potential climatic impact of cities. The difference in the ranking of low-carbon performance between the investigated cities was significant both in terms of flow-based and structural indicators. We suggest these assessment indicators of carbon metabolism be integrated into urban resources management to reflect both the decarbonization status and future emission reduction potential more accurately and to provide systemic decision support for achieving the goal of carbon neutrality in cities.