Urban and river flooding:Comparison of flood risk management approaches in the UK and China and an assessment of future knowledge needs

Increased urbanisation,economic growth,and long-term climate variability have made both the UK and China more susceptible to urban and river flooding,putting people and property at increased risk.This paper presents a review of the current flooding challenges that are affecting the UK and China and the actions that each country is undertaking to tackle these problems.Particular emphases in this paper are laid on(1) learning from previous flooding events in the UK and China,and(2) which management methodologies are commonly used to reduce flood risk.The paper concludes with a strategic research plan suggested by the authors,together with proposed ways to overcome identified knowledge gaps in flood management.Recommendations briefly comprise the engagement of all stakeholders to ensure a proactive approach to land use planning,early warning systems,and water-sensitive urban design or redesign through more effective policy,multi-level flood models,and data driven models of water quantity and quality.     

Urban flood risk assessment using sewer flooding databases

Sustainable water management is a global challenge for the 21st century. One key aspect remains protection against urban flooding. The main objective is to ensure or maintain an adequate level of service for all inhabitants. However, level of service is still difficult to assess and the high-risk locations difficult to identify. In this article, we propose a methodology, which (i) allows water managers to measure the service provided by the urban drainage system with regard to protection against urban flooding; and (ii) helps stakeholders to determine effective strategies for improving the service provided. One key aspect of this work is to use a database of sewer flood event records to assess flood risk. Our methodology helps urban water managers to assess the risk of sewer flooding; this approach does not seek to predict flooding but rather to inform decision makers on the current level of risk and on actions which need to be taken to reduce the risk. This work is based on a comprehensive definition of risk, including territorial vulnerability and perceptions of urban water stakeholders. This paper presents the results and the methodological contributions from implementing the methodology on two case studies: the cities of Lyon and Mulhouse.     

Multi-Objective Optimal Design of Detention Tanks in the Urban Stormwater Drainage System: LID Implementation and Analysis

Under the influences of climate change and rapid urbanization, extreme rainfall events become more and more intensive and the urban flooding issues have been frequently faced in many cities in the world. Previous practical and scientific experiences have demonstrated that appropriate utilization of detention facilities and low impact development (LID) devices for urban region design could be important and effective ways to the flooding control and drainage service management of an urban stormwater drainage system (USDS). This paper investigates the optimal design and application of detention tank network and LID devices for achieving these multiple objectives in the USDS. The framework and method of LID-based multi-objective optimal design of detention tanks in USDS is first developed in this study, and a practical case in SA city of China is then taken for the application. The results of this study confirm the feasibility and validity of the proposed methodological framework for the LID-based multi-objective optimal design of detention tanks in the USDS. Specifically, both total investment costs and flooding risk have been greatly reduced by the optimal implementation of the detention tank and LID measures. Meanwhile, the results indicate that the LID devices may have global effect to the flooding control and the detention tanks can be locally efficient to reduce the flooding risk. Finally, the findings of this study are discussed in the paper for their practical implications to the practical design and management of USDS.     

我国水利公共投资影响因素分析

分析影响我国水利公共投资的因素表明:水旱灾害对水利公共投资有明显影响,其中水灾更能刺激政府加大水利投入;第一产业和第二产业对水利公共投资有不同的影响方向;地方财政收入水平与水利公共投入之间是正相关关系;城市化水平越高,对水利公共投入的需求越大;地域分布也对水利公共投资带来影响。     

Flood Hazard Assessment and Management: Interface with the Public

The understanding of how people evaluate and respond to natural hazards in an urban area, and how this knowledge can be integrated in the planning and management process, are becoming very important elements of a comprehensive and participatory approach to flood hazard management. Such an approach demands a clear comprehension of the processes of the risks perception, causal attribution, possible solutions for the problem and patterns of behaviour developed during hazard situations. The willingness of the public to participate in flood management, and the attitudes to previous initiatives also need to be addressed. The provision of structural flood defences can have a major impact on the environment and there has been an expression of concern by many members of the public for the degradation of river corridors. In this context, it is becoming a commonly accepted practice by central or local governments to submit flood management plans to public discussion. Appropriate techniques for interfacing with the public are necessary to support this upsurge of public involvement. This paper presents results from research on public perception of floods, flood management and participatory initiatives in Setúbal, Portugal. An extensive interview programme was undertaken with residents and shopkeepers – with and without flood experience, professionals responsible for dealing with flood control problems and local authorities responsible for decision-making on flood management. The paper concludes with a number of recommendations for flood hazard management policy making and processes.     

Floodplain Inundation Analysis Combined with Contingent Valuation: Implications for Sustainable Flood Risk Management

This study presents the results of open-ended contingent valuation method (CVM) to estimate the residents’ maximum willingness to pay (WTP) for flood insurance and structural flood control measures in the Neka River Basin in Northern Iran. Flood inundation analysis and floodplain risk mapping were conducted by applying the HEC-RAS model combined with GIS analysis. A calibrated 100-year flood risk inundation map was considered as a basis for this research. This paper demonstrates applicability of CVM combined with flood inundation analysis to understand public participation for flood risk management, and their perception of flooding, considering associated socioeconomic and environmental factors. The results have shown that stated WTPs significantly varies with household income, distance people live from the river and the land use type of properties. Findings of this study suggest that the majority of respondents view flood hazard as the most important natural disaster. Furthermore, WTPs are significantly higher for those who have high level of flood risk perception. Three policy options for flood risk management are discussed, which include flood zoning and land use regulation, flood insurance program, and structural measure of levee construction. The advantages and disadvantages of each option are explored. It was concluded that a combination of possible mitigation options should be considered in order to achieve sustainable flood risk management in the Neka River Floodplain.     

Urban stream overflow probability in a changing climate: Case study of the Seoul Uicheon Basin,Korea

Flooding from the overflow of rivers and streams can cause major disruption in urban areas that is likely to have significant effects on human activities and the environment. Such consequences could be exacerbated by enhanced levels of precipitation resulting from future climate change. Various options are available for responding to flooding; however, further studies are needed to improve the design flood criteria in order to cope with the uncertainties of a changing climate. This study investigated an improved methodology for the evaluation of the overflow probability of urban streams. This was achieved through the application of Monte Carlo simulations (MCSs) and climate change scenarios that incorporated an increased probability of overbank flooding. An estimation of the probability of future rainfall in the Uicheon Basin of Korea, using chaos disintegration with regional climate model (RCM) scenario data, indicated a projected increase of 4.4%–9.6%. The results for 100-year flooding under projected conditions of climate change, based on a hydrologic overflow inundation model, showed that flooded areas could increase by 58.1% compared with current levels, depending on the climate change scenarios. However, forecasts based on MCSs indicated that extreme rainfall could increase by 94.9%. Thus, an overflow analysis that reflects both extreme hydrologic events and more frequent flooding due to climate change could provide a more reliable means of forecasting extreme events, as well as helping to prevent natural disasters associated with unexpected extreme flooding. The results obtained in this study would provide useful data for stakeholders and decision makers to both enhance policy standards and formulate measures to reduce the risk of urban flooding within the context of a changing climate.     

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.     

Emerging citizen contributions,roles and interactions with public authorities in Dutch pluvial flood risk management

ABSTRACT

This article focuses on the emerging role of citizens and their increasing contributions to local pluvial flood risk management in the Netherlands. A qualitative research approach is followed with semi-structured interviews, and analysis of policy documents and media reports. A typology of physical resources and actions, knowledge and advocacy activities shows evidence of locally focused citizen contributions to pluvial flood risk management in the Dutch city of Arnhem. We find that this emerging citizen role is being shaped by traditional authority-led interactions, creative and dialogical approaches to citizen engagement, and citizen-initiated contributions that then interact with authorities.     

A comprehensive approach and methods for glacial lake outburst flood risk assessment,with examples from Nepal and the transboundary area

Like other mountainous areas, Nepal is highly vulnerable to glacial lake outburst floods (GLOFs), and this vulnerability has increased due to climate change. Risk reduction strategies must be based on a comprehensive risk assessment. A comprehensive methodological approach for GLOF risk assessment is described and illustrated in case studies of the potential GLOF risk posed in Nepal by four glacial lakes, one located in China. People, property and public infrastructure (including hydropower plants, roads and bridges) are vulnerable, and there is a need to integrate GLOF risk reduction strategies into national policies and programmes.     

Estimation of uncertainty in long term combined sewer sediment behaviour predictions, a UK case study.

There are regulatory driven requirements for UK water companies to reduce the number of properties at risk of sewer flooding. One of the potential causes of sewer flooding is the presence of persistent sediment deposits in sewers. This is a common problem in many combined sewers. Although the regulation is risk based, there is a gap in current knowledge on how risk assessment is affected by the uncertainty in sewer solids behaviour prediction. This paper describes a UK case study exploring the possibility of estimating uncertainty in sewer sediment deposit level predictions, using Monte Carlo simulations combined with a response database.     

Policies and Strategies to Overcome Barriers to Rainwater Harvesting for Urban Use in Ethiopia

The Ethiopian government has been working on rainwater harvesting (RWH) for more than three decades. Despite its efforts, the results are not as expected. Different barriers have posed challenges to promoting RWH in Ethiopia. This study was done to identify the main problems and obstacles, and reflect on potential solutions. As a result, absence of clear policy definitions, lack of sustainably implemented projects, poor societal perceptions of RWH, local professionals lacking proper knowledge, and initial investment costs are found to be major causes of poor outcomes. Considering the site-specific nature of water issues, the authors propose various management strategies such as policy-oriented promotion, formulation of design guidelines, proactive planning, collaborative research, and integration of RWH with cost covering practices.     

How Did Balance Loss Occur? A Cross-stakeholder Analysis of Risk Misallocation in a Sponge City PPP Project

To address a growing number of risk misallocation issues amongst stakeholders, this study explored critical factors that influence risk misallocation from a cross-stakeholder perspective. Based on the framework of risk management, the Sponge City Program, in Guyuan City (China), was taken as a case study. The checklist of risk identification was employed to screen and rank the overall project risks, and risk assessment was conducted via a structured questionnaire survey. Logistic regression analysis was adopted to investigate the causes of the misallocation between risk control capability and willingness to take risks for both public and private stakeholders. The findings indicated that public stakeholders were more likely to be affected by information asymmetry, and contract negotiation ability; while risk misallocation for the private stakeholders tended to be affected by market policy, information asymmetry, contract negotiation ability, and financing ability. This insight can inform future studies on risk allocation in PPP water projects for public and private stakeholders to optimize the decision-making process.

     

Towards Adaptation to Climate Change: Water for Rice in the Coastal Wetlands of Doñana,Southern Spain

Rice production in coastal wetlands provides critical ecosystem services that range from flood control to wildlife habitat. In the Iberian Peninsula rice was introduced in the 10th Century. Today Iberian rice accounts for about one quarter of the total rice production of the European Union, almost exclusively cultivated in the coastal wetlands of Spain, with permanent flooding. The intensive water management required to produce rice stands at a crucial point since freshwater supply is deteriorating at an unprecedented rate. Here we explore flexible adaptation options to climate change in the Doñana wetlands - a world heritage and biodiversity site - from two points of view: What are the policy options for agricultural water management in view of climate change? How can informed stakeholders contribute to better adaptation? The first question is addressed by simulating water availability to farmers with the WAAPA model under a range of adaptation policy options derived from the view of the local communities. The second question was addressed by means of participatory research. Adaptation options are framed according to the local environmental, social and policy context. Results suggest that perception on the potential role of new water infrastructure and farming subsidies dominates the view of local communities. The choices of the stakeholders that could be simulated with the hydrological model, were quantified in terms of additional water availability for the rice farming, therefore providing a quantitative measure to the qualitative solutions. Information provided during the study shaped the final adaptation options developed. Our research contributes to the definition of sustainable rice production in Europe.     

Sustainable Urban Water System Transitions Through Management Reforms in Ghana

Despite decades of water reforms, Ghana’s struggle to achieve sustainable urban water system is deepened by complex interactions of multi-layered political, socio-economic and managerial characteristics, leaving a rationing system of water supply in major cities like Accra. Using a multi-level perspective framework, the paper examines the dynamics of urban water system transition through management reforms. The study showed how external pressure at the landscape level influenced policy direction within urban water regime through the implementation of neo-liberal economic policies, paving way for resistance and grassroots innovation at the niche level. The implementation of such policies in the reform process did little to help achieve the desired sustainable urban water system goals. The paper suggests a blend of public and private financing with support for grassroots to improve urban water system management. However, subsequent urban water policy reforms must be informed by knowledge of social, economic, and political realities rather than imported generic “best policies and practices” that often conflict with local realities.     

Monitoring of human enteric viruses and coliform bacteria in waters after urban flood in Jakarta, Indonesia.

Floodwaters in Kampung Melayu village, Jakarta, Indonesia, as well as river water and consumable water (including groundwater and tap water) samples in flooded and non-flooded areas, were quantitatively analysed to assess occurrence of viruses and total coliforms and E. coli as bacterial indicators after flooding event. High numbers of enterovirus, hepatitis A virus, norovirus (G1, G2) and adenovirus were detected at high concentration in floodwaters and waters sampled from Ciliwung River which runs across metropolitan Jakarta and is used widely for agriculture and domestic purposes by poor residents. One out of three groundwater wells in the flooded area was contaminated with all viruses tested while no viruses were found in groundwater samples in non-flooded areas and tap water samples. The results revealed that human enteric viruses, especially hepatitis A virus and adenovirus, were prevalent in Jakarta, Indonesia. This study suggested that flooding posed a higher risk of viral infection to the people through contamination of drinking water sources or direct contact with floodwaters.     

水淹厂房风险分析

以大亚湾、岭澳核电厂水淹厂房概率风险分析为例,介绍了在压水堆核电厂水淹厂房概率风险分析的方法.该方法的优势在于,通过建立发电厂数学模型,定量计算发电可能存在的风险,找到发电厂的关键敏感设备,以及其设计上的薄弱环节.     

基于知信行模型的我国居民洪灾风险感知评价

居民的灾害风险感知水平对防灾减灾政策的实施具有重要影响。以KAP模型(知识-态度-行为,Knowledge-Attitude-Practice)为理论框架,从知识、态度和行为3个方面构建了我国居民洪灾风险感知的评价指标体系。通过网络问卷调查获取数据,利用序关系分析法计算指标权重,构建了洪灾风险感知指数,用于对居民的风险感知水平进行评价。评价结果表明:①我国居民的洪灾态度表现最为积极,平均得分为7.84分;其次为洪灾行为,平均得分为6.45分;洪灾知识最为匮乏,平均得分仅为6.28分。②居民洪灾风险感知水平整体不高,平均得分7.83分;多数调查样本处于中低水平,分别占样本总量的36.50%和46.01%。建议政府合理开展洪灾宣传教育和应急演练;社区应做好防灾减灾准备,制定科学的应急预案;居民应积极关注洪灾信息、学习防洪减灾知识。     

A Comparative Study of the Performance of Public Water Rights Allocation in China

Pubic water rights allocation, in which water resources are allocated to users administratively as shared public property, is an effective and powerful policy for water resource management. Dozens of public water right allocation systems have been established in China since 1998 without any unified standard across the country. An indicator-based assessment approach, based on equity, efficiency and sustainability, is proposed in this study to evaluate the performance of public water rights allocation systems in China in a quantitative way. The approach was applied in 11 river basins of China in which water rights have been defined. The results show that the performance of the allocation systems depends on the spatial density and exploitation ratio of the water resources. The performance of allocated water rights systems is better in river basins with greater resource densities and smaller water exploitation ratios. This assessment approach is very useful for evaluating policy options for public water rights allocation with appropriate consideration of the local conditions of the river basins.     

Floodplain Residents' Preferences for Non-Structural Flood Alleviation Measures in the Red River Basin,Manitoba, Canada

Abstract

Based on the assumption that there is a general gap in information about social aspects of flood/floodplain management, the authors undertook several surveys on rural and urban residents' preferences for selected non-structural flood alleviation measures in the Red River basin, following the 1997 flood of the century. In addition to regular multiple choice and preference scaling questions, each survey contained a discrete choice experiment (a stated preference approach) which allows explicit modeling of tradeoffs. For this purpose, respondents were shown a set of choice cards displaying varied profiles of hypothetical flood/floodplain management policies and each of the respondents was asked to select the most preferred profile from a set. The survey on emergency flood evacuation indicated that in their preferences for evacuation procedures, residents were sensitive to the level of risk present. The majority of the residents preferred voluntary evacuation at the 50 percent risk of hazardous flooding, but had no objection to mandatory evacuation at a 99 percent level of risk. The choice experiment was less successful in modeling preferences for floodproofing policies. In that case, the majority of respondents consistently preferred the option of floodproofing their homesteads, irrespective of the incentives that other policy options had provided. Some of the additional survey questions suggested that the absence of a typical tradeoff behavior might have been due to the fact that a government policy on floodproofing had already been announced. The latter might have unduly influenced the responses to the hypothetical scenarios. We conclude the paper by suggesting that social science research can make significant contributions to the management and policy design of non-structural flood alleviation measures, especially when investigating management options and outcomes in a tradeoff context.