Flood Mitigation Projects Research Articles

A sensitivity analysis approach of multi-attribute decision making technique to rank flood mitigation projects

The goal of this study is to evaluate and rank the effectiveness of the Korean governments’ Four Major River Restoration Projects. A hydraulic simulation model and geographic information system tools are used to analyze the flood mitigation effects provided by these projects. In addition, the rankings of four major rivers are derived using two sensitivity analyses to weight values and performance measures for Multi-Attribute Decision Making (MADM) technique. As a result, the flood risk presented by the Nakdong River can be most effectively decreased when considering these weights, and levee freeboards are the most critical criterion in the effectiveness ranking. The Youngsan River’s flow capacity criterion is also critical for this problem. This study will be helpful in the robust prioritization of various water resources plans.

Integrated multi-criteria flood vulnerability approach using fuzzy TOPSIS and Delphi technique

Abstract. This study aims to develop a new procedure that combines multi-criteria spatial vulnerability analysis with the traditional linear probabilistic risk approach. This approach is named integrated fuzzy flood vulnerability assessment because it combines the watershed-based vulnerability framework with stream-based risk analysis. The Delphi technique and pressure-state-impact-response framework are introduced to objectively select evaluation criteria, and the fuzzy TOPSIS technique is proposed to address the uncertainty of weights to all criteria and crisp input data of all spatial units. ArcGIS is used to represent the spatial results to all criteria. This framework is applied to the south Han River basin in South Korea. As a result, the flood vulnerability ranking was derived and vulnerability characteristics of all spatial units were compared. This framework can be used to conduct a prefeasibility study for flood mitigation projects when various stakeholders should be included.

Co-conception of integrated flood management solutions: riverscapes to facilitate dialog

When involved late in flood mitigation projects, biologists can suggest only minor changes. Conception should be multidisciplinary from the start. Riverscapes appear an excellent support to exchange information and share common conceptual views. Biologists thus summarize their expertise and local analyses, including a description of the potential biodiversity and processes. We built a riverscape typology for Polish mountain rivers and used it as a support to discuss compromises and adaptations for dry dams and river training. Translating the technical solutions into shift of types guide the choices. Serving a purpose, the typology is case-dependant and could be revised during a project. Riverscapes could also potentially be useful in multidisciplinary research.

유역치수계획을 위한 대안수립: 영산강 유역의 사례연구

본 연구는 기존에 공학적 분석에 주로 치중하였던 대안수립 방법을 개선하여 경제적 측면에서 최적사업규모를 고려하는 방법을 제시하기 위한 것이다. 이를 위해서 치수사업을 투입과 산출에 의한 생산활동으로 정의하고 투입과 산출조합들을 최적화하는 방식의 대안수립 방안을 제시하였다. 본 논문은 제시된 방법론에 대한 사례연구로서 영산강유역 치수계획을 위한 대안들을 최적사업규모 결정을 통해 수립하였다. 최적사업규모 결정 결과, 최적대안의 순편익이 대안 내의 대규모 단위사업안들의 순편익에 의해 좌우되는 경향이 나타났다. 이러한 문제로 인해 상대적으로 소규모의 단위사업안들은 그 효과가 과소평가되어 최적대안으로부터 제외될 소지가 있으며, 결과적으로 이들로부터 보호받는 잠재적 피해지역들이 치수사업에서 소외될 수 있다. 따라서 피해지역별로 선택적인 홍수방어를 위해서는 단위사업안들을 홍수방어 범위에 따라 전역적 홍수방어대책과 지역적 홍수방어대책으로 분류할 필요가 있는 것으로 사료된다. The purpose of this study is to propose the alternative development method by means of determining the optimal project size from the economic viewpoint, improving the existing method depending on engineering aspects. To this end, this study defined the flood mitigation projects as the production activities carried out by inputs and outputs, and proposed the alternative development method on the basis of optimizing input and output combinations. This paper, as the case study of the proposed method, developed alternatives for the flood mitigation planning of Youngsan River Basin by determining the optimal project scale. As the result of determining optimal project size, the net benefit of the optimal alternative tended to be dependent on the net benefits of the large individual proposals. Due to such problem, the effect of relatively small individual proposals are underestimated and possibly be excluded from the optimal alternative, which may result in exclusion of the potential damaged regions protected by them from the flood mitigation project. Thus for the selective flood protection by region, individual proposals need to be categorized into the global measures and local measures according to the flood protection area.

최적사업규모 결정을 통한 유역치수계획의 대안수립 방안

유역단위의 통합적 치수계획은 고려되는 단위사업의 수가 많고 그 특성도 다양하므로 이들을 조합한 최적의 대안을 수립하기가 쉽지 않다. 최적의 대안수립을 위해서는 홍수피해를 산정하는 것뿐만 아니라 감내할 수 있는 피해의 수준을 결정해야만 한다. 이에 대한 결정은 큰 틀에서 '사회적 합의'라는 방식으로 도출되지만 일차적으로는 기술적으로 가능한 범주에서 경제적 효율성 측면의 분석을 필요로 한다. 본 연구의 목적은 각 단위사업들의 조합이 경제적 효율성을 갖도록 하는 대안수립 방법을 제시하는 것이다. 이를 위해서 치수사업을 투입과 산출에 의한 경제학적 생산활동으로 정의하고 최적사업규모를 대안수립의 원칙으로 제시하였다. 본 연구는 기존에 공학적 측면에만 의존하던 대안수립 방법을 개선하여 경제적 측면에서 최적사업규모를 고려하였다는 데에 의의가 있다. 이러한 대안수립 방법은 하천중심의 소극적 치수계획을 지양하고 피해지역 중심의 유역단위 치수계획 수립으로 전환되고 있는 최근의 정부정책 방향에도 부합하며, 정책수립을 위한 효과적인 수단을 제공할 수 있을 것으로 기대된다. The integrated basin-wide flood mitigation planning has a numerous individual proposals with different characteristics. So, it makes difficult to develop the optimal alternative that combines such elements. To develop the optimal alternative, it's necessary not only to assess the flood damage but also to define a tolerable degree of damage. Such a definition is made in a way, dubbed the 'social consensus' in a broad sense; but initially, it requires the analysis of the economic efficiency within a scope, which is technically achievable. This study aims to propose the alternatives development method so that the combination of the individual proposals could be economically efficient. To this end, this study defined the flood mitigation projects as the economic production activities carried out by inputs and outputs, and proposed the optimal project size as the principle of developing alternatives. This study may have the worth in improving the alternatives development method by considering the optimal project scale from the economic viewpoint while the existing method depending on engineering aspect. Such approach is expected to correspond to the current government's policy that avoids the passive flood mitigation focused on channel-wide planning but pursues the basin-wide flood mitigation planning focusing on damaged area, thereby provide efficient tools to come up with the solution.

Alternative risk measure for decision-making under uncertainty in water management

Taking into account uncertainties in water management remains a challenge due to social, economic and environmental changes. Often, uncertainty creates difficulty in ranking or comparing multiple water management options, possibly leading to a wrong decision. In this paper, an alternative risk measure is proposed to facilitate the ranking or comparison of water management options under uncertainty by using the concepts of conditional expected loss and partial mean. This measure has the advantages of being more intuitive, general and could relate to many other measures of risk in the literature. The application of the risk measure is demonstrated through a case study for the evaluation of flood mitigation projects. The results show that the new measure is applicable to a general decision-making process under uncertainty.

Proving the ecosystem value through hydrological modelling

Ecosystems provide valuable functions. Also natural floodplains and river structures offer different types of ecosystem functions such as habitat function, recreational area and natural detention. From an economic stand point the loss (or rehabilitation) of these natural systems and their provided natural services can be valued as a damage (or benefit). Consequently these natural goods and services must be economically valued in project assessments e.g. cost-benefit-analysis or cost comparison. Especially in smaller catchments and river systems exists significant evidence that natural flood detention reduces flood risk and contributes to flood protection. Several research projects evaluated the mitigating effect of land use, river training and the loss of natural flood plains on development, peak and volume of floods. The presented project analysis the hypothesis that ignoring natural detention and hydrological ecosystem services could result in economically inefficient solutions for flood protection and mitigation. In test areas, subcatchments of the Danube in Germany, a combination of hydrological and hydrodynamic models with economic evaluation techniques was applied. Different forms of land use, river structure and flood protection measures were assed and compared from a hydrological and economic point of view. A hydrodynamic model was used to simulate flows to assess the extent of flood affected areas and damages to buildings and infrastructure as well as to investigate the impacts of levees and river structure on a local scale. These model results provided the basis for an economic assessment. Different economic valuation techniques, such as flood damage functions, cost comparison method and substation-approach were used to compare the outcomes of different hydrological scenarios from an economic point of view and value the ecosystem service. The results give significant evidence that natural detention must be evaluated as part of flood mitigation projects. In addition can be stated that the loss of detention due to land use and dikes can be called an externality and results in economic inefficiencies.

FLOODPLAINS AND HOUSING VALUES: IMPLICATIONS FOR FLOOD MITIGATION PROJECTS1

ABSTRACT: The hedonic valuation method was used to quantify the impact of floodplain location on housing values in Fargo‐Moor‐head. Being located in the 100‐year floodplain lowered the home values by $8,990, and such homes were worth $10,241 less than similar homes located outside the floodplain before the major flood event of 1997. Required flood insurance premiums for these homes were determined to account for approximately 81 percent of this price depreciation. In contrast, homes in the 500‐year floodplain were worth $3,100 more than similar homes not in the floodplain. It was concluded that more disclosure is needed regarding the location of the 500‐year floodplain, and that the hedonic valuation method can be used to calculate the economic gains and losses associated with flood mitigation projects or floodplain remapping efforts that result in the reclassification of the legal floodplain status of individual homes.

Intangible Flood Damage Quantification

Flooding is a natural disaster that may cause tremendous tangibleand intangible damage to the national economy. The tangible damage assessment, i.e. the monetary value of all direct and indirect physical damages, has already been studied, whileintangible damages have not yet been taken into account. Thisarticle, therefore, is the first systematic attempt to assess bothtangible and intangible damages. The new proposed ‘Anxiety-Productivity and Income Interrelationgship Approach (API)’ has been developed to quantify the intangible damage in monetary terms. The Bangkok area has been selected as the research area because several severe flood events have occurredthere over the last two decades. The 1983 Bangkok flood caused 6600 million baht in damage, according to estimates by the National Statistical Office (NSO). This article examines the totalflood damage (including the intangible damage) at different flood magnitudes. Case studies ‘with’ and ‘without’ flood mitigation projects are studied and compared. Furthermore, thisarticle also discusses the improvements over the conventional approach offered by the new API methodology.

バングラデシュ北西部の地形・洪水特性からみた水害対策計画の問題点

The World Bank has made “Bangladesh Action Plan for Flood Control” which consists of 26 components after severe floods of 1987 and 1988. Japanese and UK governments donate the Component No.2, for Northwest Region. The author attended the preliminary study in 1990 as a geomorphologist and found some problems on flood mitigation projects related with characteristics of landform and flood feature.The northwest region is divided into the following four geomorphological units: 1) Barind Tract, 2) the Himalayan piedmont plains, 3) the Alluvial lowland along the Brahmaputra-Jamuna and 4) the Alluvial lowland along the Ganges. The embankments are frequently broken by floods because river beds are unstable in the Himalayan piedmont plains. In the alluvial lowland along the B.-Jamuna, the river channels are unstable and change their courses frequently during annual floods with breaching embankments, since the B.-Jamuna changed its course in the 18th century. In the alluvial lowland along the Ganges, distinct large natural levees have developed along the Ganges and a broad back-marsh area lies along the lower Atrai Basin. The “Polder Project” for flood protection is progressing in the lower Atrai Basin. However, each polder is too broad to protect the whole area. In order to protect their houses, people often cut embankments for draining inundation water not only from inside of the polder to river, but also from outside of the polder into the protected area.In the Flood Action Plan, the World Bank proposed two major projects in this area, namely, an interceptor drain from the Upper Atrai into the B.-Jamuna, and a diversion channel from the Lower Atrai into the Ganges. The main technical problem on both the Interceptor and the Diversion channel is the water level at the outfalls. The Interceptor is proposed along the Karatoya-Atrai, a heavy free-meandered river. The Interceptor needs high embankments whole from the Atrai to the B.-Jamuna. The Diversion channel is less feasible ; since the river bed of the Atrai is lower than that of the Ganges.Apart from these major projects, the author suggests smaller but reasonable projects for this area. In the southern part, the Polder Project is to be improved: smaller units of polders with consideration of geomorphological setting and local land-use conditions. A comprehensive project which contains both structural and non-structural methods for flood control and rural development programs as waterside district will support the development of this area.

Political Responses to Natural Hazards: Social Movement Participation Following a Flood Disaster

While much research attention has been focused recently upon understanding and interpreting social movements which emerge in response to technological hazards, comparatively little work has been directed toward the systematic examination of factors related to protest activity in the aftermath of natural hazards. The authors study community activism after a major flood mitigation project failed to provide the promised protection from stormwater damage. They conclude that citizen response to natural events is becoming far less distinct from that witnessed in the aftermath of man-made events, because the technology to mitigate impacts of natural disasters is becoming more available. The results of the study show that solidarity is a necessary ingredient for social movement facilitation, particularly when the movement is loosely structured and urgently organized, and that the presence of solidarity aids in the communication of grievances, recruitment of members, and the coordination of activities.

Sinkhole management and flooding in Jamaica

More than 518 km2 (200 mi2) of prime lands in Jamaica lay on Karstic material where sinkholes are the natural outlet of important streams. Due to increasing social pressure, the lands are inappropriately managed and as a consequence, vegetal debris and silting have plugged the sinkholes which have thus lost their capacity to drain the runoff produced during heavy rainfalls. One of these areas is Cave Valley, which during the last 36 years, has been affected by at least six floodings, some of which have produced losses of life and property, in a sector of the Jamaican population which is already under severe economic hardship. A flood prevention and mitigation project is being implemented including watershed management, river training and community preparedness. A geologic, hydrologic, and hydraulic analysis are also part of this study. All these measures are expected to reduce future losses.