Sensitivity of the Red River Basin Flood Protection System to Climate Variability and Change

An original modeling framework for assessment of climate variation and change impacts on the performance of complex flood protection system has been implemented in the evaluation of the impact of climate variability and change on the reliability, vulnerability and resiliency of the Red River Basin flood protection system (Manitoba, Canada). The modeling framework allows for an evaluation of different climate change scenarios generated by the global climate models. Temperature and precipitation are used as the main factors affecting flood flow generation. System dynamics modeling approach proved to be of great value in the development of system performance assessment model. The most important impact of climate variability and change on hydrologic processes is reflected in the change of flood patterns: flood starting time, peak value and timing. The results show increase in the annual precipitation and the annual streamflow volume in the Red River basin under the future climate change scenarios. Most of the floods generated using three different climate models had an earlier starting time and peak time. The assessment of the performance of Red River flood protection system is based on the flood flows, the capacity of flood control structures and failure flow levels at different locations in the basin. In the Assiniboine River Basin, higher reliabilities at downstream locations are obtained indicating that Shellmouth reservoir plays an important role in reducing downstream flooding. However, a different trend was identified in the Red River Basin. The study results show that flood protection capacity of the Red River infrastructure is sufficient under low reliability criteria but may not be sufficient under high reliability criteria.     

Comparison of Compensatory and non-Compensatory Multi Criteria Decision Making Models in Water Resources Strategic Management

Growing water demands as well as inconsistency between water demand and water supply pose new challenges for water resources managers in arid regions. This study examines the strategies to tackle water shortage for a sustainable development in Shahrood, Iran. A contentious plan has been proposed to transfer water from the Caspian Sea in north of Iran to this region. Ensuring sustainable development, however, necessitates a strategic planning for water resources. The study develops all viable strategies for the region using Strengths, Weaknesses, Opportunities, and Threats (SWOT) analysis. Due to inability of the SWOT model to rank the alternatives, the developed strategies are ranked using Multi Criteria Decision Making (MCDM) models based on specified sustainable development criteria. The ranking is implemented using the compensatory models of Simple Additive Weighting (SAW) and Analytical Hierarchy Process (AHP), and the non-compensatory model of ELimination and Choice Translating REality (ELECTRE III). The results of all MCDM models introduce water transfer as the worst strategy for the region. Because of the uncertainty in the relative importance of specified criteria, sensitivity analysis is done for MCDM models by altering the criteria weights. The results show that the ELECTRE III method has lower sensitivity than the SAW and AHP methods to changes in the weights. Also, the compensatory methods exhibits a high dependency to the weights of some dominant criteria. Therefore, this research reveals that the rankings obtained from the ELECTRE III method are more reliable for decision makers to ensure a sustainable development in the region.     

Identification of Spatial Ranking of Hydrological Vulnerability Using Multi-Criteria Decision Making Techniques: Case Study of Korea

Potential flood damage (PFD), potential streamflow depletion (PSD), potential water quality deterioration (PWQD), and watershed evaluation index (WEI) have been developed to spatially quantify the hydrological vulnerability using multi-criteria decision making (MCDM) techniques. All criteria are selected on the basis of a sustainability evaluation concept (pressure-state-response model), and their weights are estimated by an Analytic Hierarchy Process, which is also a type of MCDM technique. The MCDM techniques used for the evaluation are composite programming, compromise programming, ELECTRE II, Regime method, and Evamix method; these techniques can be classified according to data availability and objectives (prefeasibility and feasibility). Furthermore, the WEI is improved to reflect the preferences of the residents with regard to management objectives through weights (of PFD, PSD, and PWQD) obtained from questionaires of residents. Finally, this study derives a procedure to identify the spatial investment prioritization using four indices.     

Flood Vulnerability Analysis by Fuzzy Spatial Multi Criteria Decision Making

Prioritization the sub-basins available in a basin to flood vulnerability analysis can be discussed in the form of a spatial multi criteria decision making (SMCDM) problem. In this research a fuzzy planning support system based on the spatial analysis using tow multi criteria decision making methods, Analytic Hierarchy Process (AHP) and TOPSIS (Technique for order-preference by similarity to ideal solution) is used. AHP method is used to determine the structure of decision making process and to estimate criteria weights and TOPSIS model is used to rank the sub-basins of Tehran urban basin as a study area regarding the flood vulnerable areas. Also in order to perform spatial analysis for decision-making process, a developed toolbox is used within the Geographic Information System (GIS). In this research a model is presented in which some vague concepts such as weight of decision making criteria are expressed in the form of linguistic variables to be converted to triangular fuzzy numbers. Finally, the sensitivity of model was analyzed by changing the weights of decision making criteria and providing of ranking scenarios. The results show the optimum alternatives for mitigation flood vulnerability in the study area.

     

Flood Vulnerability to Climate Change through Hydrological Modeling

Abstract

Determination of flood vulnerability to climate change is one of the most critical issues for regional water management. Most of the previous studies related to system vulnerabilities to climate change were either a qualitative assessment without the support of hydrological modeling or too complex to apply them to real-world systems. In this study, a modeling and assessment system is proposed to tackle flood vulnerability to the climate change through the incorporation of future climate change scenarios, rainfall-runoff simulation, and vulnerability estimation within an integrated frame. The developed approach is applied to provide decision support for flood management of the Swift Current Creek watershed in Western Canada. The approach not only is useful to determine relative flood vulnerabilities to climate change for supporting flood control planning in the watershed, but also can be extended to estimate vulnerabilities of water quality and water supply to climate change.     

Spatial Assessment of Climate Risk for Investigating Climate Adaptation Strategies by Evaluating Spatial-Temporal Variability of Extreme Precipitation

In response to the impacts of extreme precipitation on human or natural systems under climate change, the development of climate risk assessment approach is a crucial task. In this paper, a novel risk assessing approach based on a climate risk assessment framework with copula-based approaches is proposed. Firstly, extreme precipitation indices (EPIs) and their marginal distributions are estimated for historical and future periods. Next, the joint probability distributions of extreme precipitation are constructed by copula methods and tested by goodness-of-fit indices. The future joint probabilities and joint return periods (JRPs) of the EPIs are then evaluated. Finally, change rates of JRPs for future periods are estimated to assess climate risk with the quantitative data of exposure and vulnerability of a protected target. An actual application in Taiwan Island is successfully conducted for climate risk assessment with the impacts of extreme precipitation. The results indicate that most of regions in Taiwan Island might have higher potential climate risk under different scenarios in the future. The future joint probabilities of precipitation extremes might cause the high risk of landslide and flood disasters in the mountainous area, and of inundation in the plain area. In sum, the proposed climate risk assessing approach is expected to be useful for assisting decision makers to draft adaptation strategies and face high risk of the possible occurrence of natural disasters.

     

汛限水位实时动态控制的概率多目标优选方法

方案优选对于汛限水位实时动态控制至关重要。可行方案集中的指标权重及各方案目标特征值将直接影响各方案的最终排序,在汛限水位实时动态控制中,二者通常受各种不确定性因素的影响,取值处于一个变化的范围内,而以往的优选方法对此考虑较少。为此,在HydeK.M.等人研究工作的基础上,建立方案概率优选方法,该方法不但能够优选出概率意义下的满意方案,而且能够提供方案的排序可靠度、相应于各排序的概率及方案优选目标值的累积概率分布值,从而为决策者提供更加全面的决策信息支持。实例计算验证了该方法的有效性和可行性。     

Flood Control Operations Based on the Theory of Variable Fuzzy Sets

Flood control decisions are often involved with quantitative and qualitative criteria. In this paper, a decision model is presented for flood control operations based on the theory of variable fuzzy sets. Using dual comparison, two models computing relative membership grades with qualitative and quantitative criteria are established, respectively. A method integrating subjective preference and iterative weights is proposed for weight-assessment. First, an initial solution of criteria weights is obtained by using proposed fuzzy optimal iteration model. Then, according to their knowledge related to real time flood operations, operators may modify the initial weights if necessary. When the relative membership grades of alternatives belonging to all rankings are fixed by using multi-criterion variable fuzzy model proposed, the decision alternative is chosen according to the ranking characteristic value computed using a defuzzification equation. The case study of Fengman Reservoir flood operation (in China) is provided to illustrate the application of the proposed method. With the incorporation of operator’s knowledge related to flood operations, the proposed model is flexible and practical.     

Margin of Safety Based Flood Reliability Evaluation of Wastewater Treatment Plants: Part 1 – Basic Concepts and Statistical Settings

Low-lying coastal urban areas are vulnerable to frequent and chronic flooding due to population growth, urbanization, and accelerated sea level rise originating from climate change. This paper is part one of a 2 paper series, however a detailed literature review on the concept and the technical aspects of both papers is presented. In the 2nd paper, the application of the concepts and the proposed methodology are utilized to set the mitigation strategies for quantification of reliability attributes. The case study is the Hunts Point wastewater treatment plant and its sewershed in Bronx, New York City. The suitability of two major rainfall stations of Central Park and LaGuardia airport in the vicinity of the case study is tested. The copula-based non-stationary 100–year flood frequency analysis of rainfall and storm surge is analyzed to obtain the design values of surge and rainfall. A differential evaluation Markov Chain with Bayesian interface is used in this paper for parameter estimation. In this study, the likelihood of joint probability of co-occurring heavy rainfall and storm surge is determined to illustrate the risk of joint events. Therefore, the copula-based non-stationary 100–year flood frequency analysis of rainfall and storm surge are performed to obtain the design values of surge and rainfall. A multi-criteria decision-making (MCDM) approach that incorporates the load-resistance concept is presented in Part 2 paper to assess the Margin of Safety flood reliability of a wastewater treatment plant (WWTP). The framework presented in this paper is applicable to other coastal sewersheds.

     

Targeting attention on local vulnerabilities using an integrated index approach: the example of the climate vulnerability index.

It is known that climate impacts can have significant effects on the environment, societies and economies. For human populations, climate change impacts can be devastating, giving rise to economic disruption and mass migration as agricultural systems fail, either through drought or floods. Such events impact significantly, not only where they happen, but also in the neighbouring areas. Vulnerability to the impacts of climate change needs to be assessed, so that adaptation strategies can be developed and populations can be protected. In this paper, we address the issue of vulnerability assessment through the use of an indicator approach, the climate vulnerability index (CVI). We show how this can overcome some of the difficulties of incommensurability associated with the combination of different types of data, and how the approach can be applied at a variety of scales. Through the development of nested index values, more reliable and robust coverage of large areas can be achieved, and we provide an indication of how this could be done. While further work is required to improve the methodology through wider application and component refinement, it seems likely that this approach will have useful application in the assessment of climate vulnerability. Through its application at sub-national and community scales, the CVI can help to identify those human populations most at risk from climate change impacts, and as a result, resources can be targeted towards those most in need.     

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.     

A Fuzzy-Stochastic Modeling Approach for Multiple Criteria Decision Analysis of Coupled Groundwater-Agricultural Systems

The complexity of water resources management increases when decisions about environmental and social issues are considered in addition to economic efficiency. Such complexities are further compounded by multiple uncertainties about the consequences of potential management decisions. In this paper, a new fuzzy-stochastic multiple criteria decision-making approach is proposed for water resources management in which a variety of criteria in terms of economic, environmental and social dimensions are identified and taken into account. The goal is to evaluate multiple conflicting criteria under uncertainties and to rank a set of management alternatives. The methodology uses a simulation-optimization water management model of a strongly interacting groundwater-agriculture system to enumerate criteria based on these bio-physical process interactions. Fuzzy and/or qualitative information regarding the decision-making process for which quantitative data is not available are evaluated in linguistic terms. Afterwards, Monte Carlo simulation is applied to combine these information and to generate a probabilistic decision matrix of management alternatives versus criteria in an uncertain environment. Based on this outcome, total performance values of the management alternatives are calculated using ordered weighted averaging. The proposed approach is applied to a real world example, where excessive groundwater withdrawal from the coastal aquifer for irrigated agriculture has resulted in saltwater intrusion, threatening the economical basis of farmers and associated societal impacts. The analysis has provided potential decision alternatives which can serve as a platform for negotiation and further exploration. Furthermore, sensitivity of different inputs to resulting rankings is investigated. It is found that decision makers’ risk aversion and risk taking attitude may yield different rankings. The presented approach suits to systematically quantify both probabilistic and fuzzy uncertainties associated with complex hydrosystems management.     

Economic assessment of climate adaptation options for urban drainage design in Odense, Denmark

Climate change is likely to influence the water cycle by changing the precipitation patterns, in some cases leading to increased occurrences of precipitation extremes. Urban landscapes are vulnerable to such changes due to the concentrated population and socio-economic values in cities. Feasible adaptation requires better flood risk quantification and assessment of appropriate adaptation actions in term of costs and benefits. This paper presents an economic assessment of three prevailing climate adaptation options for urban drainage design in a Danish case study, Odense. A risk-based evaluation framework is used to give detailed insights of the physical and economic feasibilities of each option. Estimation of marginal benefits of adaptation options are carried out through a step-by-step cost-benefit analysis. The results are aimed at providing important information for decision making on how best to adapt to urban pluvial flooding due to climate impacts in cities.     

An Evaluation of Climate Change Impacts on Extreme Sea Level Variability: Coastal Area of New York City

Climate change has resulted in sea level rise and increasing frequency of extreme storm events around the world. This has intensified flood damage especially in coastal regions. In this study, a methodology is developed to analyze the impacts of climate change on sea level changes in the coastal regions utilizing an artificial neural network model. For simulation of annual extreme sea level, climate signals of Sea Surface Temperature, Sea Level Pressure and SLP gradient of the study region and some characteristic points are used as predictors. To select the best set of predictors as neural network model input, feature selection methods of MRMR (Minimum Redundancy Maximum Relevance) and MI (Mutual Information) are used. Future values of the selected predictors under greenhouse gas emission scenarios of B1, A1B and A2 are used in the developed neural network model to project water level for the next 100 years. Sea levels with different recurrence intervals are determined using frequency analysis of historical and projected water level as well, and the impact of climate change in extreme sea level is investigated. The developed methodology is applied to New York City to determine the coastal region vulnerability to water level changes. The results of this study show remarkable increase in sea level in the New York City, which is an indicative of coastal areas vulnerability and the need to take strategic actions in dealing with climate change.     

深圳河流域内陆侧洪涝风险分析

基于致灾因子、孕灾环境、承灾体与防灾减灾能力四大风险要素对深圳河流域内陆侧的洪涝风险进行分析,构建以雨、洪、潮叠加的复杂致灾因子危险性和高度城市化带来的高易损性为特征的沿海城市洪涝灾害风险评价指标体系,用层次分析法修正熵权法以确定评价指标的权重,得到洪涝的危险性风险、易损性风险和综合风险区划。结果表明：福田区西南部至罗湖区西南部是极高危险性与极高易损性的统一体,在防洪减灾中应予以较全方位的重点防护,其他低易损性且高危险性地区只需根据主导的危险性因子给予有所侧重的防护措施;构建的沿海城市洪涝灾害风险评价指标体系可为政府防灾减灾规划与防洪应急响应提供必要的参考依据,亦可为防灾资源分配和灾后恢复重建提供有效信息。     

Extreme floods and river values: A social–ecological perspective

The social–ecological status of rivers is particularly pronounced during extreme flood events. Extreme floods are a substantial threat to people, infrastructure, and livelihoods. Efforts to address the threats of extreme floods are aligned largely with social values of flood risk mitigation, flood preparation, and avoidance of loss. However, extreme floods are also a fundamental driver of river ecosystems, aligned with ecological (biophysical) values of event effectiveness, river change, disturbance, biotic response, and heterogeneity. A survey of the public perceptions of extreme floods revealed that participants generally understood the ecological values of extreme floods through concepts of naturalness, climate change, and knowledge production. However, participants had less understanding of how river integrity might influence the response of rivers to extreme floods. Resilience can be used as a framework for uniting the social and ecological values of extreme floods because it embodies a common language of change, disturbance, and adaptation and complements the socially dominated discourse of risk and emergency management. Three strategies are given for river scientists to frame ecological values in parallel with the paradigms of the socially dominated discourse of extreme floods: be prepared to act following an extreme flood disaster, learn and use the language of the flood risk and emergency management sector, and undertake assessments of the ecological values of extreme floods to highlight the threats to those values that may occur with climate change and river modification.     

我国沿海城市洪潮组合风险分析

针对沿海城市防洪安全和经济可持续发展的问题,从气候变化和人类活动两个方面对沿海城市洪涝事件的成因进行了归纳。以深圳市为例,选取大沙河上游西沥水库站和深圳湾赤湾潮位站为代表站,基于Copula函数,对深圳市洪潮组合进行风险分析。结果表明,虽然降水和高潮位的双阈值组合风险率小于单域值组合风险率,但深圳市同时遭遇暴雨和高潮位时所造成的城市洪涝灾害更为严重,经济损失和人员伤亡更为巨大;在城市防洪防潮排涝规划、设计时需更加关注降水和潮位的双阈值组合风险率大小。     

Evaluation of Real-Time Operation Rules in Reservoir Systems Operation

Reservoir operation rules are logical or mathematical equations that take into account system variables to calculate water release from a reservoir based on inflow and storage volume values. In fact, previous experiences of the system are used to balance reservoir system parameters in each operational period. Commonly, reservoir operation rules have been considered to be linear decision rules (LDRs) and constant coefficients developed by using various optimization procedures. This paper addresses the application of real-time operation rules on a reservoir system whose purpose is to supply total downstream demand. Those rules include standard operation policy (SOP), stochastic dynamic programming (SDP), LDR, and nonlinear decision rule (NLDR) with various orders of inflow and reservoir storage volume. Also, a multi-attribute decision method, elimination and choice expressing reality (ELECTRE)-I, with a combination of indices, objective functions, and reservoir performance criteria (reliability, resiliency, and vulnerability) are used to rank the aforementioned rules. The ranking method employs two combinations of indices: (1) performance criteria and (2) objective function and performance criteria by using the same weights for all criteria. Results show that the NLDR gives an appropriate rule for real-time operation. Moreover, NLDR validation is presented by testing predefined curves for dry, normal, and wet years.     

A Fuzzy Multi-Criteria Group Decision-Making Model Based on Weighted Borda Scoring Method for Watershed Ecological Risk Management: a Case Study of Three Gorges Reservoir Area of China

In watershed ecological risk management, a series of alternatives will be analyzed in terms of multiple complex criteria, and different stakeholders with conflicting risk attitudes will be involved, which means that ecological risk management decision-making is a process surrounded by a wide range of uncertainties derived from scarcity of data, lack of knowledge, deficiency of assumptions and lexical vagueness. Based on modified Borda scoring method, this paper discusses how to apply a fuzzy multi-criteria group decision-making (FMCGDM) model into such a process. Then, a two-stage, 12-step MCDM methodology is proposed to obtain the optimal alternative decided by multiple decision-makers (DMs) from a given alternatives set. Firstly, all DMs make their own independent choice respectively, then, all the independent conclusions are integrated by using their subjective/objective weights. A modified Borda method is followed to rate and rank the weighted alternatives; in which the one with the highest score will be selected as the final preferable option. This model is demonstrated to be applicable and reliable by an application in the ecological risk decision making process of Three Gorges Reservoir area located in the upper reaches of Yangtze River in China. Of course, this method can also be applied in other research fields of environmental management.     

Spatio-temporal variation of flood vulnerability at the Poyang Lake Ecological Economic Zone, Jiangxi Province, China

For a long time areas of Poyang Lake have been threatened by floods. It is therefore important to assess flood vulnerability in this area. A composite flood vulnerability index was developed using an indicator approach to detect spatial distribution and temporal variation of flood vulnerability in the Poyang Lake Ecological Economic Zone (abbreviated to PLEEZ). Thematic maps of flood vulnerability showed a spatially ring-shaped distribution. The flood vulnerability ranking of one unit negatively correlated with the distance between the unit and the lake. Although flood vulnerability in PLEEZ declined significantly, the spatial distribution hardly changed from 1997 to 2006. The degree of flood vulnerability is highly related to exposure; variations in flood vulnerability are influenced by sensitivity and adaptive capacity. Based on correlation analysis, three proxies were identified as determinants of flood vulnerability variation over the past 10 years. This approach could provide policymakers with important flood risk information and entry points for flood management.