Assessing the effects of flood resilience technologies on building scale

The impacts of floods on housing are increasing due to more frequent and severe weather events as well as the ongoing development of settlements in flood-prone areas together with the rising vulnerability of assets at risk. Therefore, the improvement of the resilience properties of buildings to better cope with flooding has become a key issue towards more flood resilient cities in European research in recent years. The implementation of flood resilience technologies (FReT) on the individual property scale provides a previously untapped potential to reduce flood damage to buildings due to insufficient transparency of their effects. To overcome this obstacle, the paper presents a four-step extension of a synthetic approach for flood vulnerability analysis to provide evidence on the potential effects of FReT uptake concerning flood damage mitigation. The proposed approach has been integrated in the GIS-based flood damage simulation model HOWAD to support the assessment of FReT alternatives. The simulation of flood damage to buildings in the case study Heywood, Greater Manchester (United Kingdom) revealed the potential of the extended approach to determine the consequences of FReT implementation on building scale.     

Urban flood impact assessment: A state-of-the-art review

Flooding can cause major disruptions in cities, and lead to significant impacts on people, the economy and on the environment. These impacts may be exacerbated by climate and socio-economic changes. Resilience thinking has become an important way for city planners and decision makers to manage flood risks.

Despite different definitions of resilience, a consistent theme is that flood resilient cities are impacted less by extreme flood events. Therefore, flood risk professionals and planners need to understand flood impacts to build flood resilient cities. This paper presents a state-of-the-art literature review on flood impact assessment in urban areas, detailing their application, and their limitations. It describes both techniques for dealing with individual categories of impacts, as well as methodologies for integrating them. The paper will also identify future avenues for progress in improving the techniques.     

Evaluation of functional resilience in urban drainage and flood management systems using a global analysis approach

Enhancing resilience in urban drainage systems (UDSs) requires new evaluation approaches that explicitly consider vital interactions between threats, system performance and resulting failure impacts during both normal and unexpected (exceptional) loading conditions. However, current reliability-based approaches only focus on prevention of functional (hydraulic) failures resulting from a specified design storm. In this study, the global resilience analysis (GRA) approach is further extended for evaluation of UDS performance when subject to a wide range of random functional failure scenarios (extreme rainfall) with varying magnitude, duration, and spatial distribution. The resulting loss of system functionality during the simulated failure scenarios is quantified using total flood volume and mean flood duration. System residual functionality for each considered rainfall block loading scenario is quantified using the functional resilience index. The developed approach has been successfully applied to test and characterise the functional resilience to extreme rainfall of an existing UDS in Kampala city, Uganda. The study concluded that: (1) UDS functional resilience is significantly influenced by both occurrence of short duration, high intensity rainfall events and spatial rainfall variation during extreme rainfall conditions and (2) future planning and design of resilience enhancement strategies should apply spatially distributed rainfall inputs to facilitate effective sizing of potential adaptation strategies.     

高密度沿海地区洪涝风险评价与适应性规划策略 ——以深圳湾地区为例

气候变化背景下，高密度沿海城市受 到风暴潮和极端降雨引起的洪涝灾害冲击。文 章基于韧性理论构建城市空间洪涝风险指标 体系，制定该评价框架的实施路径；基于水文 软件Mike21、GIS平台及其空间网络分析插件 sDNA，复合“天鸽”台风风暴潮与极端降雨情 景，整合深圳湾地区的路网和土地利用进行危 险性、暴露度、脆弱性和适应能力等多源数据； 通过GIS栅格计算得到各要素层分析及洪涝风 险评价可视化地图，结果显示，潮、洪、涝突破 刚性标准加剧了危险性，高密度城市环境增大了 危险区域的暴露度，路网和土地利用布局具有 一定脆弱性，需完善应急疏散和避难场所规划以增强适应能力；根据评价地图识别高风险片区，从路网和土地利用等城市空间物质要素出发， 提出应对洪涝灾害的适应性规划策略。     

A systems approach to flood vulnerability

Flood vulnerability is an internationally important problem with no easy solution. In this paper it is argued that vulnerability is an emergent output of interacting human and engineering components, and that to make further progress on usefully deploying the concept, a systems approach is needed. The existing state of the art in Flood Vulnerability Indices is blended with a constraints-based systems engineering approach called an Abstraction Hierarchy. Four existing towns were modelled using this approach, and the impact of a 1–200 year flood was assessed, by focusing on the key interactions within the model. As the flood waters progressively removed physical objects in the system, higher-level processes and functions became systematically degraded. Via this process, the modelled towns were revealed to be low on exposure, high on susceptibility, but low on resilience. This is one of eight vulnerability types possible. Different flood risk solutions can be associated with different vulnerability types. Comparing these outputs to real-life policy and practice reveals some interesting areas of mismatch.     

Validating a rapid assessment framework for screening surface water flood risk

This research evaluates performance of a rapid assessment framework for screening surface water flood risk in urban catchments. Recent advances in modelling have developed fast and computationally efficient cellular automata frameworks which demonstrate promising utility for increasing available evidence to support surface water management, however, questions remain regarding trade‐offs between accuracy and speed for practical application. This study evaluates performance of a rapid assessment framework by comparing results with outputs from an industry standard hydrodynamic model using a case study of St Neots in Cambridgeshire, UK. Results from the case study show that the rapid assessment framework is able to identify and prioritise areas of flood risk and outputs flood depths which correlate above 97% with the industry standard approach. In theory, this finding supports a simplified representation of catchments using cellular automata, and in practice presents an opportunity to apply the framework to develop evidence to support detailed modelling.     

Is Bangkok becoming more resilient to flooding? A framing analysis of Bangkok's flood resilience policy combining insights from both insiders and outsiders

The rapidly urbanizing cities in Southeast Asia experience increasing flood impacts due to the consequences of climate change. In these cities, policy efforts to build flood resilience are gaining momentum. The aim of this paper is to understand and assess flood resilience policy development, particularly in cities in developing countries. Bangkok is one of the cities that participates in the 100 Resilient Cities Programme (100RC) - the international policy platform for building resilient cities. In 2017, the Bangkok Metropolitan Administration (BMA) launched the ‘Bangkok Resilience Strategy’ to translate the resilience concept to its urban context. A framing perspective is adopted to reconstruct the strategy, process and anticipated outcome of Bangkok's flood resilience policy. We studied data obtained from ‘insiders’ (involved policy makers, experts and consultants) and ‘outsiders’ (local communities, civil society organizations and news media). Findings indicate that the economic growth frame is prevailing in the development of Bangkok's flood resilience policy, prioritizing structural flood protection with little attention for flood adaptation measures and related social impacts among vulnerable communities. The role of local communities and civil society in the formulation of Bangkok's flood resilience policy is limited. This paper therefore recommends cities in developing countries and cities in the 100RC Programme to organize a more inclusive resilience building process for addressing social problems regarding urban poor communities along with increasing flood safety and protection.     

气候韧性导向的严寒地区城市设计框架——以长春市总体城市设计为例

严寒地区长达6个月以上的冬季使城市面临更加独特且多元的气候问题,如低温、冷风、冰雪等,这种复杂气候对城市安全的影响成为严寒地区城市设计亟待解决的问题。通过系统性文献综述,梳理既有研究针对城市设计要素与气候韧性关系达成的共识性认知,得到气候韧性视角下城市设计不同维度构成要素的属性特征。以此为基础,针对严寒地区独特多元的气候问题,提出包含调蓄旱涝的生态安全格局、多样连通的生物安全格局、多中心紧凑型城市形态格局、改善雾霾的多层级通风廊道格局、改善冬季光环境舒适性的公共空间体系等内容的气候韧性导向的城市设计框架,并结合住建部城市设计试点项目长春市总体城市设计进行实践应用。以期为中国严寒地区开展应对气候灾害的韧性城市设计提供方法框架和技术指引。     

Citywide multi-grid urban flood modelling: the July 2012 flood in Beijing

Global flood management is a major issue for most cities which have to deal with worsening factors such as climate change and fast urban growth. Computer models have been used to model and understand urban flooding on a local scale in cities (25–50 km²). It has been practically impossible to model bigger cities in one go in sufficiently high resolution due to the heavy computations involved.

The present paper describes a new modelling approach for urban flooding which allows modelling on large city scale (1000 km²) while keeping sufficient resolution, e.g. 5 m or 10 m grid. The multicell approach is applied for the city of Beijing for July 21st, 2012 flood event. Model results are compared to testimonials from the 2012 event. Comparison to traditional 2D urban flood computations shows that the multicell approach is much faster than standard detailed models while keeping a suitable level of precision.     

Designing,planning, and managing resilient cities: A conceptual framework

To what must cities be resilient? How can cities, as complex systems, be resilient? Building a capacity for resilience might be a daunting task when one considers the multitude of components, processes, and interactions that take place within and beyond a city’s physical, logical (i.e. legal), and virtual (cyberspace) boundaries. Planning for resilience to the impacts of stressors within cities requires an evaluation of the vulnerable components of cities, an understanding of the key processes, procedures, and interactions that organize these components and develop the capacity to address various structuring of components and their interactions with the ultimate goal of achieving resilience. This paper provides a deeper look at resilience in cities, proposes a conceptual resilience framework, and includes a discussion and analysis of the framework. The proposed framework is meant to serve as a more holistic approach to designing, planning, and managing for resilience by including an evaluation of cultural and process dynamics within cities as well as their physical elements.     

韧性城市视角下海平面上升对沿海城市的影响及对策研究——以厦门市为例

随着全球气候不断变化,海平面上升速率逐渐加快,严重影响着沿海城市的安全与可持续发展,提升沿海城市韧性已经成为其应对气候变化的战略共识。基于韧性城市理论,构建了海平面上升影响分析及韧性评价模式,并以厦门市为例,展开了不同时间情景下的影响分析及韧性评估。结果表明,2030年和2050年在海平面上升的影响下,受灾人口将增加6万人和8万人,受灾建设用地将增加5.1km^2和8.3km^2,受灾道路将增加14.6km和24.0km。同时通过空间评估,明确了不同地区韧性提升的重点。最后针对性地提出了厦门城市韧性提升的策略。     

Bayesian modeling of flood control networks for failure cascade characterization and vulnerability assessment

This paper presents a Bayesian network model to assess the vulnerability of the flood control infrastructure and to simulate failure cascade based on the topological structure of flood control networks along with hydrological information gathered from sensors. Two measures are proposed to characterize the flood control network vulnerability and failure cascade: (a) node failure probability (NFP), which determines the failure likelihood of each network component under each scenario of rainfall event, and (b) failure cascade susceptibility, which captures the susceptibility of a network component to failure due to failure of other links. The proposed model was tested in both single watershed and multiple watershed scenarios in Harris County, Texas using historical data from three different flooding events, including Hurricane Harvey in 2017. The proposed model was able to identify the most vulnerable flood control network segments prone to flooding in the face of extreme rainfall. The framework and results furnish a new tool and insights to help decision‐makers to prioritize infrastructure enhancement investments and actions. The proposed Bayesian network modeling framework also enables simulation of failure cascades in flood control infrastructures, and thus could be used for scenario planning as well as near‐real‐time inundation forecasting to inform emergency response planning and operation, and hence improve the flood resilience of urban areas.     

Soft systems methodology and integrated flood management: a study of the Adayar watershed,Chennai, India

This paper applies Soft Systems Methodology (SSM) within the context of action research and Integrated Flood Management (IFM). A case study from the Adayar watershed, Chennai, is provided as an example of how SSM can be used to understand complex situations and as a problem‐solving strategy for flood management. Flat topography, uncontrolled urban development, population growth, sand bar formation at the river mouth and low tidal action render complexity to flood management in Chennai. For effective flood management, a participatory and integrated approach, which includes stakeholders in the decision‐making process and an enabling institutional set‐up, is essential. As part of an integrated approach, the relationship between various organizations and the public is identified. SSM is an approach for addressing fuzzy problematic situations involving human activity. In this paper, SSM techniques like ‘Rich Picture Diagrams’ and ‘CATWOE analysis’ and participatory action research tools like ‘pairwise ranking’ and ‘force field analysis’ were investigated. Two workshops were conducted to define and explore the problematic situation, the role of various actors involved in the problem, to develop the conceptual model, to rank decision‐making criteria, and to analyse the forces for and against to solve the problem. The flood management approach provided in this paper can be used by government agencies and policy makers to manage floods.     

Planning for dynamic cities: introducing a framework to understand urban change from a complex adaptive systems approach

Planning for dynamic cities is a perennial problem that continues to grow in importance in a rapidly changing world. This paper presents a conceptual framework to understand urban change through a complex adaptive systems approach. This framework includes a process of (1) describing the system through setting boundaries and identifying the properties of the system, (2) identifying the patterns of change across scales and (3) mapping the change over time. The framework firstly, offers a tool to urban planners to approach some of the complexities of urban change and secondly, a foundation to engage with the challenge of developing alternative sustainable development models that are able to deal with the reality of complex, dynamic and interconnected urban systems and to cope with change and uncertainty in ways that build positive resilience and support regenerative design and development.     

Resilient urban forms: A macro-scale analysis

Cities need to build on their resilience to cope with a broad range of natural and manmade hazards that threaten their competitiveness, livability, and functionality. Recognizing this need, the resilience concept is increasingly used as an organizing principle to guide research design and facilitate a more informed decision-making process. However, despite the abundance of studies on urban resilience, research on the link between urban form and resilience is limited and fragmented. This study sheds more light on this issue by reviewing and synthesizing theoretical and empirical evidence on how physical structure of cities can facilitate or hinder urban resilience. Acknowledging that each city is located within a nested hierarchy of scales that is characterized by cross-scale dynamics, only the macro-level aspects and elements of urban form are analyzed in this paper. These are namely ‘scale hierarchy’, ‘city size’, ‘development type’, ‘degree of clustering’, and ‘landscape/habitat connectivity’. Key criteria and indicators for analyzing resilience of each element/aspect are specified and used to discuss how macro-scale urban form is related to various resilience properties such as robustness, redundancy, resourcefulness, modularity, flexibility, adaptability, and efficiency. Findings indicate that urban form has major implications for social, ecological, and economic functionality of cities and can play a key role in enhancing their resilience and sustainability.     

基于承洪韧性的老旧住区更新规划 策略研究——以天津川府新村住区为例

针对当前城市中老旧住区面临的雨洪灾害日益严重的问题,梳理国内外有关承洪韧性的相关研究,探讨承洪韧性的内涵与作用,建立了城市老旧住区雨洪管理影响要素与承洪韧性的关联框架。根据城市老旧住区的基本特征和其中普遍存在的问题,从提升可浸区百分比、提升雨水贮存率,以及提升雨水利用率等方面提出了基于承洪韧性理念的城市老旧住区更新策略。再以天津川府新村为例,针对该住区现状存在的雨洪灾害问题,模拟验证了相关策略的实施效果。     

A resilience assessment method for urban water systems

Infrastructure planning for Urban Water Systems (UWSs) is challenged by, inter alia, increasing uncertainty in both demand and availability of water and aging infrastructure, and this is already impacting the climate-proofing of cities. In this context, the idea of resilience has been gradually embraced by the water sector, but the term itself is not yet universally defined, nor operationalised. Here, we propose a methodology to assess the resilience of a UWS, defining it as the degree to which the UWS continues to perform under increasing stress. A resilience assessment method is then proposed as a ‘stress-test’ of UWS configurations, under increasingly more stressful scenarios. We then demonstrate a toolbox assembled for the proposed analysis using, as a proof of concept, a semi-synthetic case study. Results are promising, suggesting that the approach could assist in the uptake and evolution of resilience thinking in strategic water infrastructure decision making, leading to water-wiser cities.     

A framework for the future of urban underground engineering

A special and holistic approach is needed that captures aggregate attributes and emergent behaviors of the complex system of infrastructure systems in a region. Effective management of the impacts of future population growth, urbanization, and risks arising from continued evolution of our natural, physical and human/societal systems will require a systematic exploration and characterization of the urban subsurface, including much improved understanding and assessment of geologic risks. With recent cost escalations for underground construction projects, incentives are needed for the underground construction industry to develop and implement innovations in methods and technology, and smart integrated planning is needed to reduce costs both during construction and with life-cycle engineered design and operation of our subsurface facilities.The needed framework requires investigation of potential metrics that reflect the performance of aggregate functions of an urban environment so that we can holistically study system performance response under “normal” and “stressed” operation. Such a metric can support a cross-disciplinary exploration of urban resilience, and build knowledge as we develop and test theory and models that explore resilience of complex socio-technical systems. Econometrics with spatial and temporal granularity will help to understand the integrated functionality of our cities and to establish appropriate policies that will drive continuous improvement in the quality of urban life while providing natural, human, and physical urban environmental resilience. The underground in urban regions can become an important component of managing the increasing complexity of our physical systems, and can also make more significant contributions to improving the robustness and resilience of our future cities.     

Membrane assisted technology appraisal for water reuse applications in South Africa

Water scarcity, pertaining to many interrelated issues e.g. rapid urbanisation and increasing water pollution, has been acknowledged around the world. Water reuse has emerged as a viable water conservation measure to satisfy water demand in many communities. Among the diversity of wastewater treatment processes, membrane assisted treatment technologies have been employed for different water reuse scenarios. In this regard, one of the most critical problems is how to select an appropriate membrane technology for a water reuse scenario. This research therefore develops a decision making framework for selection of wastewater treatment technology. The framework is applied to different non-potable reuse scenarios in South African cities and suburban areas by employing a multi criteria analysis method. The results show that this approach is able to provide a systematic and rigorous analysis which can help in comparing and selecting wastewater technologies.     

Smart green cities: from modernization to resilience?

It is possible to detect a shift in the way we think about environmental issues, in particular climate change, from what academics call ‘ecological modernization’ to what can be termed ‘resilient cities’. This is both a consequence and a cause of city regions emerging as the pragmatic scale of governance. This article will use a case study of Greater Manchester in the northwest of England to show how thinking on the environment was centred around ‘ecological modernization’ with an emphasis on business opportunities associated with a move to a low-carbon economy. It will argue that this approach has been enhanced by a new focus on resilience. The case study will use examples of the Ecocities project, green infrastructure and flood risk to show how a concern for resilience has emerged. It will then revisit the issue of energy to show how the new concerns have influenced the low-carbon strategy.