Decision making under deep uncertainty for adapting urban drainage systems to change

ABSTRACT

Urbanisation and climate change are augmenting the uncertainty surrounding the future state of the world’s water resource and are resulting in cities experiencing growing levels of risk of pluvial flooding. Drainage infrastructure is generally built using the paradigm of ‘predict and optimise’; however, this approach fails to account for erroneous predictions. This can result in drainage systems delivering insufficient levels of flood protection. Irrespective of these uncertainties new drainage systems must be built, and existing ones adapted in such a way that they remain reliable. This work presents a critical analysis of the drivers of change of urban pluvial flooding and the uncertainties surrounding urban flood planning; thereby highlighting the shortcomings of current planning methodologies. Different Decision Making Under Deep Uncertainty (DMDU) frameworks are then explored and it is shown that they offer an improved ability to design reliable urban flood systems regardless of highly uncertain future conditions.     

气候变化给城镇给水排水系统带来的挑战

简要介绍了国际和中国对"气候变化与水"的评估和预测结果,论述了当前有关国家和国际组织研究讨论关于城市给水排水发展应对气候变化的相关主要问题,分析了气候变化给中国城市给水排水系统带来的挑战,并提出了相应建议。     

Daily urban water supply modeling and forecasting based on the elliptic orbit model with weekly quasi-periodic extension

ABSTRACT

Modeling and forecasting for various time horizons of urban water supply are important for different operations within a utility company. This study proposes the ‘elliptic orbit model’ for daily urban water supply prediction from the viewpoint of time-series analysis. As additional efforts and costs are required to acquire and predict more different forecast variables, it is argued that many studies failed to carefully check whether such efforts and costs were deserved and to what degree they might ameliorate the prediction accuracy. Thus predictive modeling based on available water supply data has its own advantages. Only the water-supply time-sequence data is used and mapped into the polar coordinates to design the proposed ‘elliptic orbit model’, so the purpose of this study is to present one vivid approach for forecasting daily urban water supply in an intuitive and concise way. The proposed model archives satisfying experimental results and may inspire other applications.     

Impact of operating rules on planning capacity expansion of urban water supply systems

ABSTRACT

Water utilities often rely on industrial water supply (e.g. desalination) to complement natural resources. These climate-independent sources of supply allow operators to respond quickly to varying operating conditions, but require them to choose operating strategies, or rules. How does such operational flexibility impact the performance of water supply systems? How might it affect long-term plans for capacity expansion? Possibly significantly, as demonstrated by the analysis of a water supply system based on Singapore. First, we simulate the dynamics of the system under multiple rainfall and operating scenarios to understand the extent to which the operators’ behavior affect system performance. Results show that different operating rules can have comparable impact on the variability in system performance as hydrological conditions. Then, we show that small changes in the operating rules can lead to substantial changes in the capacity expansions, such as the size of a new desalination plant.     

Towards sustainable urban water management: A critical reassessment

Within the literature, concerns have been raised that centralised urban water systems are maladapted to challenges associated with climate change, population growth and other socio-economic and environmental strains. This paper provides a critical assessment of the discourse that surrounds emerging approaches to urban water management and infrastructure provision. As such, ‘sustainable urban water management’ (SUWM) concepts are scrutinized to highlight the limitations and strengths in the current lines of argument and point towards unaddressed complexities in the transformational agendas advocated by SUWM proponents. Taking an explicit infrastructure view, it is shown that the specific context of the urban water sector means that changes to infrastructure systems occur as an incremental hybridisation process. This process is driven by a range of factors including lock-in effects of legacy solutions, normative values and vested interests of agents, cost and performance certainty and perceptions of risk. Different views of these factors help explain why transformational agendas have not achieved the change SUWM proponents call for and point to the need for a critical reassessment of the system effects and economics of alternative service provision models.     

Prioritisation of abstraction boreholes at risk from chlorinated solvent contamination on the UK Permo-Triassic Sandstone aquifer using a GIS

A 250 km2 area of the Permo-Triassic Sandstone aquifer in the West Midlands of England, UK, was selected as a test region for the development of a geographic information system (GIS)-based risk assessment methodology that incorporates contaminant source, groundwater vulnerability and groundwater abstraction catchment elements in order to prioritise areas and boreholes potentially at risk from chlorinated solvent pollution on a regional scale. Factors incorporated in the vulnerability assessment include the nature of soils, presence or absence of superficial or glacial deposits, fault density and depth to water table. ARCVIEW GIS was employed with a simple ranking system from which the derived vulnerability assessment index was combined with current chlorinated solvent user industry data and source protection zone components. Results indicate the presence of high-risk areas in urban locations where locally dense distributions of chlorinated solvent user industries combine with high vulnerability aquifers within the catchment of supply boreholes. Ranking of catchment-specific risk reveals the abstraction points under greatest stress. The proposed methodology has applications as a regional-scale initial screening tool to guide site selection for regulatory inspections and assist in prioritising monitoring strategies for existing boreholes. Future developments will provide guidance for locating new urban boreholes in areas of lowest risk.     

Urban hydrology and water management – present and future challenges

Urban hydrology is an applied science that will have an increasing role to play in the sustainability of human societies. Facing present growth of urban population, it is increasingly difficult to find and utilize new sources of water necessary to satisfy growing water demand. For the poor, the residents of peri-urban and squatter areas, an ultimate poverty, the poverty of lacking clean water, is a result. To remove this kind of poverty should be a first priority target for all people and, especially, for people dealing with water management in urban areas. Growth of urban areas brings significant changes in physical properties of land surface increasing integrated vulnerability of inhabitants, agricultural land and rural ecological life supporting systems. Performance of technical solutions depends on climate as well as on social, economical and cultural conditions. Findings from urban hydrological studies based on collection of urban hydrological data, calculations and modeling constitute a necessary fundamental for meaningful water management not only in urban areas but also in entire river basins. Future challenges in urban water management include development of new technical solutions as well as logistic and organizational methods in order to turn present problems into future opportunities. The following current and emerging challenges are discussed in the paper: delivery of drinking water supply for growing cities, water for sanitation versus sanitation without water, recycling of wastewater nutrients, wastewater irrigation, urban agriculture, water to feed depleted aquifers, thoughts about possible future new system solutions, social equity and transfer of knowledge and new technology.     

Three Points Approach (3PA) for urban flood risk management: A tool to support climate change adaptation through transdisciplinarity and multifunctionality

Urban flood risk is increasing as a consequence of climate change and growing impervious surfaces. Increasing complexity of the urban context, gradual loss of tacit knowledge and decreasing social awareness are at the same time leading to inadequate choices with respect to urban flood risk management (UFRM). The European Flood Risk Directive emphasises the need for non-structural measures aimed at urban resilience and social preparedness. The Three Points Approach (3PA) provides a structure facilitating the decision making processes dealing with UFRM. It helps to accept the complexity of the urban context and promotes transdisciplinarity and multifunctionality. The 3PA introduces three domains wherein water professionals may act and where aspects valued by different stakeholders come into play: (1) technical optimisation, dealing with standards and guidelines for urban drainage systems; (2) spatial planning, making the urban area more resilient to future changing conditions; and (3) day-to-day values, enhancing awareness, acceptance and participation among stakeholders. Based on in-depth interviews conducted in The Netherlands and Denmark, we describe the complexity of decision making in practical UFRM and explain how the 3PA can be used when organising participatory processes. We introduce a theoretical framework characterising the large range of aspects involved in decision making related to UFRM and evaluate the usefulness of the 3PA in dealing with it. We conclude that the 3PA offers water managers and operators an efficient communication tool and thinking system, which helps to reduce complexity to a level suitable when organising strategy plans for UFRM and urban adaptation to climate change.     

Coping with Global Environmental Change,Disasters and Security: Threats,Challenges, Vulnerabilities and Risks

Since the publication of the third assessment report of The Intergovernmental Panel on Climate Change, vulnerability to climate change has become an important research question. Vulnerability assessment on the urban scale has become a major issue. This paper describes a conceptual framework for modelling vulnerability at the urban scale, the Climate Change Vulnerability Assessment model. The model is applied to Shanghai, a typical geographically vulnerable and rapidly-urbanizing case study area. Using Arc-GIS, a vulnerability map was created for understanding the spatial dynamics of climate change vulnerability in Shanghai. An additional process, combined with the weighting coefficients, produced different vulnerable areas. Based on the vulnerability map, we located several high risk areas. The vulnerability of each area was assessed. Identifying the risks in each case and associating them with a specific region can be useful for decision makers.     

Feeding the global city: urban transformation and urban food supply chain in 21st-century Istanbul

ABSTRACT

This article focuses on the effects of urban transformation on the urban food supply chain in 21st century Istanbul. The article begins with a discussion on the particularities of the urban transformation that has shaped the city since the 1980s, emphasizing tendencies that are relevant to food consumption and supply patterns and practices. Next, 6 categories of fresh fruits and vegetables (FFVs), provisioning agents (mixed/foreign-capital supermarkets, domestic-capital supermarkets, bazaars, local suppliers, and urban and semi-urban/peripheral farmers, internet or store-based alternative food networks) are analyzed in terms of their perception of urban transformation and various challenges it poses. The article concludes with an assessment of the changes in the city’s food supply chain in light of provisioning agents’ responses to the urban transformation as a force that either enables them compete more successfully and expand their operations or pushes them to contract or even leave the provisioning sector completely.     

Comparison of engineering costs of raw freshwater, reclaimed water and seawater for toilet flushing in Hong Kong

Hong Kong is one of the very few coastal cities in the world that use ‘dual water supply systems’. Dual water supply involves two distribution systems: a freshwater system for potable use and a seawater system for toilet flushing. This study looks into the feasibility, from an engineering cost point of view, of extending seawater supply into districts where potable water is still being used for toilet flushing, including South District of Hong Kong Island, Sai Kung, Northern New Territories and Northwest New Territories. Besides seawater, raw (untreated) freshwater and reclaimed water (treated effluent from local sewage treatment works) are also considered to be used for toilet flushing for these districts. Six cases are developed for comparison by using the lowest net present value of cost criterion. The result shows that using seawater for toilet flushing in these districts has the best engineering economy.     

基于层次分析和风险矩阵法的城市供水系统风险评估

以J市供水系统为研究对象,运用风险矩阵法和层次分析法对该市供水系统的风险进行了分析.结果表明,J市供水系统的风险等级接近Ⅲ级;原水系统和制水系统的风险等级达到Ⅲ级,且风险因素主要集中在自然因素、基础设施与设备设施三个方面;输配水系统及二次供水系统的风险等级为Ⅱ级,需要加强管理.同时,根据风险评估结果提出了相应的风险对策...     

Maximising the benefits of rainwater harvesting technology towards sustainability in urban areas of South Africa: a case study

ABSTRACT

Rainwater harvesting (RWH) technology has been in use for a long time, however its contribution towards urban water supply has been negligible in South Africa. Through a comprehensive literature review and analysis of interviews with key stakeholders, this case study presents implementation challenges and policy gaps in relation to the scale of adoption in the City of Johannesburg (CoJ). Findings show that only 0.1% of CoJ’s population utilises RWH due to various reasons, varying from financial viability, reliability, quality concerns, and system maintenance. This paper attributes these to the scale of adoption and suggests upscaling the system to larger commercial buildings to optimise benefits. However, there is an urgent need to bridge the policy gaps for successful implementation. Three categories of policy reforms are therefore proposed to facilitate innovation uptake, stakeholder engagement and compliance. This knowledge can guide future research towards urban water management, scientists and policymakers nexus.     

上海气候变化脆弱性评估与治理对策

随着全球气候变化加剧，针对特大型沿海城市进行气候变化脆弱性评估及适应性对策研究，可保障城市健康安全发展。构建上海气候变化城市脆弱性评价体系，并对现状进行评估。发现上海为中度脆弱；气候变化背景下气候灾害发生风险增加，高度城市化的上海受损可能性增加；上海在自然空间保护、经济结构以及社会福利方面表现较好，对气候变化敏感性和适应性表现较好。分析上海面临的气候变化问题，提出应对策略，为上海预防气候性灾害、建设适应性城市提供参考依据。     

A probabilistic framework for multi-hazard risk mitigation for electric power transmission systems subjected to seismic and hurricane hazards

Abstract

Many areas of the world are prone to multiple hazards that can be concurrent/non-concurrent and dependent/independent. Infrastructure systems located in such areas will likely be subjected to more than one hazard in their lifetime. The damage due to such hazards on electric power systems is well documented. Over the years, strategies to mitigate single hazards have been proposed for electric power systems. However, accurate long-term decisions on investment in risk mitigation strategies require the consideration of multiple hazards that can impact a system over its lifespan. Therefore, there is a need to investigate the cost-effectiveness of mitigation strategies in reducing risks to infrastructure systems that are vulnerable to multiple hazards given the constraints on resources. This requires a comprehensive multi-hazard risk assessment approach. This paper presents a framework for investigating the effectiveness of multi-hazard risk mitigation strategies for electric power systems subjected to seismic and hurricane wind hazards. The framework includes probabilistically weighted deterministic hazard analysis model, component vulnerability models, topologically based system performance model, component importance measure appropriate for networked systems, and life cycle cost analysis. A notional electric power network assumed to be located in Charleston, SC, and New York, NY, is used to demonstrate the proposed framework.     

城市燃气管网的震害分析及减灾对策

通过分析地震对城市燃气管网的破坏作用及其引发的次生灾害,给出了燃气管网的震害特征和主要影响因素,包括地震动强度、场地条件、管道特性等。有针对性地提出了相应的抗震减灾对策,包括加强燃气工程设施的抗震设计,对燃气管网实施腐蚀监测和剔旧更新,设置燃气紧急自动切断系统与分区域供气,开展受损管网故障排查与恢复供气,建立地震实时监测和震害快速分析系统,制定能反映震后真实情景模式的应急反应预案,建立城市燃气管网震害风险评价和模拟仿真系统等。     

TRNSYS simulation for solar-assisted liquid desiccant evaporative cooling

ABSTRACT

Recently, desiccant cooling systems are well thought of as a competent method for controlling the water content in the air. A solar flat-plate collector has been used as it decreases the dependency on non-renewable resources. Solar-aided liquid desiccant systems have been used to reduce the dependency of air-conditioning systems on non-renewable sources of energy. Manipal’s humid and searing climate provides certain benefits in setting up such a system. The suggested system has reliability and equipment life and also takes complete advantage of the available solar energy for the renewal of the liquid desiccant. TRNSYS simulation is used to predict the efficiency and feasibility of the system. The temperature and energy-load variations were successfully obtained. An effective simulation was developed whereby the solar air conditioning of a room was indicated.     

Transition to a water-cycle city: risk perceptions and receptivity of Australian urban water practitioners

Transition to a water-cycle city, a sustainable urban water management future, requires the implementation of centralised and decentralised systems to augment potable water supply, protect waterways and enhance urban liveability. Risk is simultaneously driving and impeding this transition. However, risk perceptions of water practitioners and how they affect practitioner receptivity to future modes of urban water supply are poorly understood. This study characterises risk perceptions and attitudes of Australian urban water practitioners towards alternative water systems and uses a receptivity framework to suggest how receptive practitioners are to these systems. Differences between cities are identified, suggesting how familiarity might influence receptivity. These results can inform strategies to enhance receptivity, including improved communication within the water industry and beyond with its various stakeholders, improved cost-projection frameworks to provide a quantitative metric of the benefits of sustainable water options, and a shift from ‘learning to manage’ to ‘managing to learn’.     

Quantitative microbial risk assessment with respect to Campylobacter spp. in toilets flushed with harvested rainwater

In light of increasing pressures on water supplies in some areas, water demand management and water conservation techniques are likely to become increasingly prevalent. In‐house systems using alternatives to mains supplies for nonpotable uses present one such option for reducing potable water demand. This paper, through a formal desk‐based health impact assessment (HIA) and quantitative microbial risk assessment (QMRA), examines one of the possible health implications (Campylobacter infection from toilet flushing) resulting from the use of rainwater harvesting in the home in the United Kingdom. This is investigated using data from the literature and a hypothetical case study population of over 4000 people (based on data for the ‘average’ population in England), with the results being expressed as disability‐adjusted life years (DALYs) (on an annual basis) and placed in context of the ‘tolerable’ risk from drinking‐water supplies.     

Economic implications of water efficiency measures I: assessment methodology and cost-effectiveness of micro-components

Economic efficiency has recently become one of the primary objectives of water management decisions. In particular, as vulnerability of freshwater systems has become evident and there is a trend for water supply managers to look towards water demand management, identifying the cost of such measures is becoming increasingly important. In England and Wales, Part G of the Building Regulations requires that water consumption of a new dwelling should not be more than 125 litres/capita.day. However, while compliance with this is determined by the water use characteristics of the installed micro-components (WCs, showers, basin taps, kitchen taps, baths, dishwashers and washing machines), the cost to consumers resulting from installing water efficient micro-components is not clear. This paper evaluates the potential economic implications of water saving micro-components, assessed from the consumers’ perspective. A methodology has been developed and implemented to assess the cost-effectiveness of several types of water efficient micro-components. A range of cost assessment methods was applied, and critically reviewed comparing their outcomes. It was found that conventional cost assessment methods are unsuitable for identifying the least cost options to consumers. Of the applied methods, the modified annualised assessment method appears to be a relatively better option.