流域未来洪水风险动因响应关系定性分析方法的研究

流域未来洪水风险的情景分析,涉及到众多自然因素、人为因素以及这些因素之间复杂的相互作用关系。为构建未来洪水风险情景、开展未来预见研究,借鉴英国已有的研究经验,提出了流域未来洪水风险动因响应关系的定性分析方法,该方法有助于清楚地分析洪水灾害系统中各因素之间的关系、各因素影响洪水风险的作用机制,以及它们影响未来洪水风险的趋势。文中以太湖流域为研究对象,通过描述影响流域未来洪水风险的重要因素,建立起各因素之间的洪水风险动因响应关系,并判断了各因素影响未来洪水风险的重要性和不确定程度,从而为研究流域未来洪水风险提供了必要的基础信息。     

The efficiency of asset management strategies to reduce urban flood risk

In this study, three asset management strategies were compared with respect to their efficiency to reduce flood risk. Data from call centres at two municipalities were used to quantify urban flood risks associated with three causes of urban flooding: gully pot blockage, sewer pipe blockage and sewer overloading. The efficiency of three flood reduction strategies was assessed based on their effect on the causes contributing to flood risk. The sensitivity of the results to uncertainty in the data source, citizens' calls, was analysed through incorporation of uncertainty ranges taken from customer complaint literature. Based on the available data it could be shown that increasing gully pot blockage is the most efficient action to reduce flood risk, given data uncertainty. If differences between cause incidences are large, as in the presented case study, call data are sufficient to decide how flood risk can be most efficiently reduced. According to the results of this analysis, enlargement of sewer pipes is not an efficient strategy to reduce flood risk, because flood risk associated with sewer overloading is small compared to other failure mechanisms.     

Assessing the legitimacy of flood risk governance arrangements in Europe: insights from intra-country evaluations

Legitimacy has received comparatively less attention than societal resilience in the context of flooding, thus methods for assessing and monitoring the legitimacy of flood risk governance arrangements are noticeably lacking. This study attempts to address this gap by assessing the legitimacy of flood risk governance arrangements in six European countries through cross-disciplinary and comparative research methods. On the basis of this assessment, recommendations to enhance the legitimacy of flood risk governance in Europe are presented.     

变化环境下洪涝风险演变特征与城市韧性提升策略

在全球气候变暖与快速城镇化的背景下，极端暴雨洪涝发生的可能性与不确定性在增大，同时洪涝威胁对象、致灾机理、成灾模式、损失构成与风险特性均在发生显著变化。本文基于郑州“7.20”特大暴雨水灾的实地调研与典型案例的剖析，阐述当代社会洪涝风险连锁性、突变性、传递性的演变机理与趋向，结合国际社会与水共存、韧性提升的理念与实践，探讨变化环境下与新时代基本国情相适宜的洪涝灾害防治策略。研究结果表明，应对快速城镇化进程中极端暴雨洪涝灾害，需以流域为单元做好综合治水的统筹规划；韧性城市只有建成不怕淹的城市，才有利于实现人水和谐的目标；在发展不均衡、不充分的现实条件下，完善与健全洪涝灾害风险管理与应急管理体制与运作机制，不仅在于保障安全，而且要为新时代经济社会快速平稳发展保驾护航。     

Community resilience following extreme disturbances: The response of ground beetles to a severe summer flood in a Central European lowland stream

Extreme environmental events are predicted to increase in future due to global climate change. However, their effects on biodiversity still remain insufficiently understood because of the rarity and consequently the difficulty of studying the effects of extreme events. Here, we investigate the impacts on ground beetles of an unpredictable catastrophic flood event of the Elbe River in Germany in the year 2002 using pre‐ and post‐flood data. We analysed the response of grassland communities differentially exposed to flooding and focused on the question of how long their response lagged behind this extreme flood. Ground beetles were sampled from 1998 to 1999 (pre‐flood period) and from 2002 to 2006 (post‐flood period) on 48 floodplain grassland plots with a stratified randomized sampling design. Community resilience was quantified by calculating changes in species richness, species abundances, Simpson diversity and beta diversity of ground beetle assemblages. Ground beetles showed low resistance but high resilience to the extreme flood. Species richness decreased strongly immediately after the flood but reached pre‐flood values 2 years later. However, beta diversity remained relatively high in the subsequent years indicating persistent shifts in species composition and abundances. Contrary to our expectation, assemblages inhabiting plots prone to flooding, expected to be less sensitive to floods, did not recover faster than those on rarely inundated plots. We considered both the timing and the long duration of the flood as main reasons for the low community resistance to the flood. Strategies related to dispersal and habitat generality are identified to be crucial for the quick community recovery following the extreme flood. Our results endorse that extreme floods are integral parts of functioning floodplain ecosystems and that species can cope well even with such unpredictable extreme events, although recovery time tends to be longer than after normal floods. Copyright © 2010 John Wiley & Sons, Ltd.     

The evolution of UK flood insurance: incremental change over six decades

In this paper, the authors' theorizing shifts away from the catalytic role of the flood itself – or other crises – towards a deeper understanding of the relationship between change and stability, taking the example of UK flood insurance and the agreements – and the implicit policy approaches – between the actors involved: private insurers and the government. The study relies upon in-depth analysis of policy agreements governing flood insurance since the 1960s, and semi-structured interviews with six current or former flood insurance professionals. The important agents of change have been, firstly, threats to existing household insurers from new entrants unencumbered by agreements to insure all comers. Secondly, technological changes have made exposure more explicit and pricing risk both easier and less expensive. The slow pace of change and the relatively stable role of the different actors and coalitions is now clearer. Many windows of opportunity created by major flooding or financial crises have not significantly affected the pace or direction of policy change. The overriding importance of the London location for – and the profitability of – the insurance industry, both to government and to the insurers, explains the extraordinary policy stability described here. This history suggests that the UK may not be a good model for imitation elsewhere.     

Development of a method for assessing flood vulnerability.

Over the past few decades, a growing number of studies have been conducted on the mechanisms responsible for climate change and the elaboration of future climate scenarios. More recently, studies have emerged examining the potential effects of climate change on human societies, including how variations in hydrological regimes impact water resources management. According to the Intergovernmental Panel on Climate Change's third assessment report, climate change will lead to an intensification of the hydrological cycle, resulting in greater variability in precipitation patterns and an increase in the intensity and frequency of severe storms and other extreme events. In other words, climate change will likely increase the risks of flooding in many areas. Structural and non-structural countermeasures are available to reduce flood vulnerability, but implementing new measures can be a lengthy process requiring political and financial support. In order to help guide such policy decisions, a method for assessing flood vulnerability due to climate change is proposed. In this preliminary study, multivariate analysis has been used to develop a Flood Vulnerability Index (FVI), which allows for a comparative analysis of flood vulnerability between different basins. Once fully developed, the FVI will also allow users to identify the main factors responsible for a basin's vulnerability, making it a valuable tool to assist in priority setting within decision-making processes.     

2020年鄱阳湖洪水回顾与思考

2020年6月底始,受持续强降雨和长江干流顶托倒灌影响,鄱阳湖水位暴涨,发生超历史纪录大洪水。基于水库、堤防、蓄滞洪区和非工程措施组成的鄱阳湖防洪体系现状,分析了2020年鄱阳湖洪水的雨情、水情和灾情特点,总结了鄱阳湖防洪体系在应对2020年洪水中取得的成效、存在的问题。提出要适应江湖自然节律,学会与洪水共生存,坚持束疏结合、重点防御、人力与技术防汛相结合、工程与非工程措施相结合,实施洪水风险管理,协调好湖泊治理与保护的关系等治水理念。     

粤港澳大湾区城市洪涝问题及其分析

近年来,粤港澳大湾区城市洪涝问题日趋严峻。本文梳理了大湾区典型城市洪涝事件,归纳了洪涝特征并分析了洪涝问题的主要驱动要素。结果表明,近100多年,大湾区年降雨量、降雨日平均雨量、暴雨日数及暴雨日降雨量占全年比例都波动增加,而降雨日数波动减少,降雨呈现增多且趋于集中的态势。大湾区降雨时空分布不均,近10年广州、东莞、惠州汛期降雨量占全年雨量的81%,广州龙舟水期间降雨量占全年约22%。虽然大湾区城市群呈现热岛效应,气温与城镇化率呈正相关,且100多年来各城市温度上升并与降雨量呈正相关;但受地理位置影响,各城市降雨量与其城镇化率的关系并不明显,而更下游的沿海城市面临更多的锋面雨和台风雨影响。近10年给大湾区带来暴雨以上降雨的台风有47场,发生在6—10月,其中恰逢天文大潮的有21场、有26场在大湾区以西登陆。近40年珠江口沿海海平面上升速率3.5 mm/a,高于全国平均水平,海平面的持续上升将使大湾区面临严重洪涝风险。对强降雨、台风暴潮、海平面变化等要素开展分析可为大湾区防灾减灾工作提供重要参考。     

Scenario-based hydrodynamic simulation of adaptive strategies for urban design to improve flood resilience: A case study of the Mingzhu Bay Region,Guangzhou, Greater Bay Area

The Pearl River Delta is a complex ecological-artificial system. The low-elevation landform and land subsidence make the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) more vulnerable to heavy rainstorms with sea-level rise in the future. Therefore, this study discussed how to optimize the delta-related built environment based on locality via cooperation between urban designers and hydrology researchers so that urban development in the GBA can adapt to water disasters. First, this study proposed three adaptive spatial strategies for urban design to improve flood resilience: (a) adding more sunken space and rearranging the locations of manholes; (b) adding more retention space to the waterway system; and (c) improving foundation elevation for suitable development intensity. With the prediction of sea-level rise and land subsidence, four different scenarios were defined. Second, a coupled 1D/2D hydrodynamic model was built for scenario-based urban inundation simulations. Third, a Python workflow was developed to reveal the water volume exchange, and an ArcMap workflow to realize the impact of inundation. The simulation results show that (a) more sunken space can lower the peak runoff discharges and decrease the runoff coefficient; (b) more retention space can extend the capacity of the urban drainage system and adapt to the rise of sea level; and (c) improving foundation elevation and more sunken green space can direct the surface water to submerge urban land in reasonable order, which can protect the significant infrastructures and development lands. This paper suggests that these adaptive spatial strategies can serve as solutions for resilience development.