Flood Mitigation Alternatives Research Articles

Multi-criteria evaluation of Safe-to-Fail flood solution alternatives for developing resilient coastal cities

ABSTRACT Safe-to-Fail (SF) is an emerging resilient design approach that envisions potential failure scenarios while designing infrastructure systems. This study aims to establish the relative weightage of the SF criteria, and, to construct a ranking of the commonly employed flood mitigation alternatives within the context of coastal flood resilience. In pursuit of these goals, this research identifies SF criteria documented in existing literature and catalogs typically used coastal flood solutions. Then, the study surveys the professionals from the Department of Transportation (DOT) and leverages a multi-criteria decision-making approach to assess the responses and develop the intended ranking. The findings highlight that robustness is the highest weighted SF criteria and ecosystem restoration is the highest-ranked SF flood solution closely followed by green infrastructure (GI). These findings provide valuable insights for decision-makers of infrastructure development in coastal cities and support them to embrace SF design strategies for developing resilient built environments.

Living with Floods Using State-of-the-Art and Geospatial Techniques: Flood Mitigation Alternatives, Management Measures, and Policy Recommendations

Flood, a distinctive natural calamity, has occurred more frequently in the last few decades all over the world, which is often an unexpected and inevitable natural hazard, but the losses and damages can be managed and controlled by adopting effective measures. In recent times, flood hazard susceptibility mapping has become a prime concern in minimizing the worst impact of this global threat; but the nonlinear relationship between several flood causative factors and the dynamicity of risk levels makes it complicated and confronted with substantial challenges to reliable assessment. Therefore, we have considered SVM, RF, and ANN—three distinctive ML algorithms in the GIS platform—to delineate the flood hazard risk zones of the subtropical Kangsabati river basin, West Bengal, India; which experienced frequent flood events because of intense rainfall throughout the monsoon season. In our study, all adopted ML algorithms are more efficient in solving all the non-linear problems in flood hazard risk assessment; multi-collinearity analysis and Pearson’s correlation coefficient techniques have been used to identify the collinearity issues among all fifteen adopted flood causative factors. In this research, the predicted results are evaluated through six prominent and reliable statistical (“AUC-ROC, specificity, sensitivity, PPV, NPV, F-score”) and one graphical (Taylor diagram) technique and shows that ANN is the most reliable modeling approach followed by RF and SVM models. The values of AUC in the ANN model for the training and validation datasets are 0.901 and 0.891, respectively. The derived result states that about 7.54% and 10.41% of areas accordingly lie under the high and extremely high flood danger risk zones. Thus, this study can help the decision-makers in constructing the proper strategy at the regional and national levels to mitigate the flood hazard in a particular region. This type of information may be helpful to the various authorities to implement this outcome in various spheres of decision making. Apart from this, future researchers are also able to conduct their research byconsidering this methodology in flood susceptibility assessment.

Case Study: analysis of flood adaptation measures through the simulation of an event in the Matina Limón river, Costa Rica

The proximity of urban and extensive agricultural areas to the rivers of the Atlantic watershed in Costa Rica contrasts with its unstable morphology. Additionally, changes on the rain regime have increased the frequency of natural disasters affecting regularly the nearby populations and the economy of the country. Detailed studies demonstrating the impact of rivers in urban areas and high agricultural activity are necessary to establish adequate flood mitigation and control measures. The present study shows a case study of the impact of a 25-year flood event on the flood plain of the Matina River in Costa Rica, by means of a bi-dimensional hydraulic modelling with the aim to contribute to the adequate management of land use and the establishment of protection measures in the study vregion. A digital elevation model, of the topography of the study area, obtained with a LIDAR device, and the estimation of the instantaneous peak flow was obtained with the statistical Weibull distribution for a return period of 25 years, allowed to provide satisfactory information for the flood analysis of complex combinations for surface drainage management. Two scenarios for flood management were analyzed: 1) increasing the dike height, and 2) early opening of an additional mouth at the river outlet during the flood events. The study demonstrated that none of the options were technically feasible and that decision makers should explore other flood mitigation alternatives.

Flood Mitigation Measures in Urban Areas of Malaysia Using the Integrated Catchment Modelling Approach

Integrated catchment modelling has been used to provide non-structural measures for the mitigation and management of urban flood prone areas. This paper aims to demonstrate a model-based approach through flood mapping that generates multiple simulation results of flood mitigation alternatives for the Sungai Gombak basin. Hydrological and hydraulic analysis, as well as hydrodynamic modelling were carried out using Infoworks Integrated Catchment Modelling (ICM) to evaluate the changes of flood extent caused by different structural components. Rainfall analyses were carried out through the computation of rainfall-runoff and design storms at various return periods and durations. Historical rainfall and stage data were used in the calibration process before the design storm events were fed into the hydrological model. Simulation of the design floods were run under different return periods, storm durations, and land use conditions. The results show that the existing rivers downstream of Sungai Gombak can only provide a flood protection level of 5 to 20-year Average Recurrence Intervals (ARIs). The main cause of frequent flooding can be attributed to the rapid change in catchment land use as development has far exceeded the Kuala Lumpur Structure Plan 2020, and the lack of compliance to the practices recommended in Manual Saliran Mesra Alam (MSMA). The findings suggest that bridge constriction removal is the key solution and that its combination with other flood mitigation works would significantly reduce the flood levels. In conclusion, the study provides useful results and a technical proposal for the authority, and successfully recommends further improvements in flood mapping practices for future studies.

Analysis of the Local Characteristics of Flood Damage Vulnerability in an Urban Area: The Han River Basin

In urban areas, the damage caused by locally concentrated heavy rainfall has recently increased due to the congestion of population and assets, high impervious ratio, and increased utilization of underground space. The extent and types of damage differ depending on the characteristics of the area. Therefore, the vulnerability to and impact of floods should be assessed according to local characteristics, and flood mitigation alternatives should be developed accordingly. In this study, the urban areas of the Han river basin were classified by flood vulnerability and damage characteristics, and the relationship between flood vulnerability and flood damage was analyzed using historical flood damage data. First, the municipalities of the Han River basin were divided into urban and non-urban areas by multivariate statistical analysis using urban factors. Next, climate exposure, sensitivity, and adaptability were used to asses flood vulnerability for 56 local governments classified as urban areas. As a result of statistical analysis, they were divided into four clusters: regions with high flood vulnerability for all factors, regions with high flood sensitivity and low adaptability, regions with low sensitivity and high adaptability, and regions with low flood vulnerability for all factors. Finally, flood damage reduction measures were suggested according to the flood damage characteristics of each cluster. Keywords: Urban Flood, Flood Vulnerability, Principal Component Analysis, Cluster Analysis

Application of real option analysis for planning under climate change uncertainty: a case study for evaluation of flood mitigation plans in Korea

With concerns regarding global climate change increasing, recent studies on adapting to nonstationary climate change recommended a different planning strategy that could spread risks. Uncertainty in global climate change should be considered in any decision-making processes for flood mitigation strategies, especially in areas within a monsoon climate regime. This study applied a novel planning method called real option analysis (ROA) to an important water resources planning practice in Korea. The proposed method can easily be applied to other watersheds that are threatened by flood risk under climate change. ROA offers flexibility for decision-makers to reflect uncertainty at every stage during the project planning period. We successfully implemented ROA using a binomial tree model, including two real options—delay and abandon—to evaluate flood mitigation alternatives for the Yeongsan River Basin in Korea. The priority ranking of the four alternatives between the traditional discount cash flow (DCF) and ROA remained the same; however, two alternatives that were assessed as economically infeasible using DCF, were economically feasible using ROA. The binomial decision trees generated in this study are expected to be informative for decision-makers to conceptualize their adaptive planning procedure.

GIS-Based Spatial Monte Carlo Analysis for Integrated Flood Management with Two Dimensional Flood Simulation

Spatial Monte Carlo Analysis (SMCA) is a newly developed Multi-Criteria Decision Making (MCDM) technique based on Spatial Compromise Programming (SCP) and Monte Carlo Simulation (MCS) technique. In contrast to other conventional MCDM techniques, SMCA has the ability to address uneven spatial distribution of criteria values in the evaluation and ranking of alternatives under various uncertainties. Using this technique, a new flood management tool has been developed within the framework of widely used GIS software ArcGIS. This tool has a user friendly interface which allows construction of user defined criteria, running of SCP computations under uncertain impacting factors and visualization of results. This tool has also the ability to interact with and use of classified Remote Sensing (RS) image layers, and other GIS feature layers like census block boundaries for flood damage calculation and loss of life estimation. The 100-year flood management strategy for Oconee River near the City of Milledgeville, Georgia, USA is chosen as a case study to demonstrate the capabilities of the software. The test result indicates that this new SMCA tool provides a very versatile environment for spatial comparison of various flood mitigation alternatives by taking into account various uncertainties, which will greatly enhance the quality of the decision making process. This tool can also be easily modified and implemented for solving a large variety of problems related to natural resources planning and management.

Assessing Flood Mitigation Alternatives in Brezovička Village in Slovakia

Abstract Flooding due to extreme rain events in urban environments is a problem and a growing concern. There is an increasing demand for a new paradigm to improve flood-mitigation decision processes that calls for riskreduction strategies at several levels. Therefore is a challenge in assessing and comparing different flood mitigation measures. The aim of this paper is to explore a new method to improve an environmental impact assessment of flood-mitigation measures in decision processes by risk analysis method.

A comparative evaluation of flood mitigation alternatives using GIS‐based river hydraulics modelling and multicriteria decision analysis

AbstractA multicriteria framework is developed for the selection of optimal flood mitigation and river training measures in a selected reach of Zaremroud River in Northern Iran. A river model, Hydrologic Engineering Center River Analysis System, combined with geographic information system analysis is used to simulate water levels for steady, gradually varied flow and mapping inundated flood extents. The modelling is performed for four different alternatives, considering various channel modifications with different dimensions and levee construction. Flood inundation area, flood level, flow velocity and stream power on the downstream and outside of the river bend are used as decision criteria for each alternative. Economic analysis is conducted to evaluate the cost‐effectiveness of each alternative. The decision analysis method, technique for order of preference by similarity to ideal solution, is used to compare different flood hazard mitigation measures based on risk, and environmental and economic impacts criteria. The findings of the analysis are that a levee construction at the right side of the river bank adjacent to the residential area is superior to the other three alternatives, which is confirmed using a scenario analysis of different flood mitigation measures.

Integrated washland optimization model for flood mitigation using multi-objective genetic algorithm

Washlands in river engineering have attracted attention as an alternative flood control facility and the promotion of biodiversity in a watershed. This article introduces an integrated washland optimization model that is developed to evaluate flood mitigation alternatives by installation of washlands in a large watershed. This model is aimed at encouraging collaboration between channels and basin storage for burden-sharing in the whole basin. The model’s effectiveness in managing flood control is evaluated using a linkage between the optimization algorithm and Unsteady NETwork program (UNET) for hydraulic routing process and flood decrement computation in basin network. For optimal scheduling of the channel and washland capacity, two objective functions are defined: maximization of the freeboard in the channel, and minimization of the washland storage area. The multi-objective genetic algorithm (MOGA) based on a rank-based fitness assign method is used for optimization of these two objectives. The results indicate the optimal location of the washlands, and thus enable the precise evaluation of the freeboard increments by hydraulic routing process according to the pareto-optimal solutions in the basin-wide channel.

Urbanization Impacts on Flooding in the Kansas River Basin and Evaluation of Wetlands as a Mitigation Measure

This study evaluates the impacts of future land use changes on flooding in the Kansas River basin. It also describes the impacts of wetlands on flood reduction. The study presents Hydrologic Engineering Center Hydrologic Modeling System (HEC-HMS) based runoff modeling and Hydrologic Engineering Center River Analysis System (HEC-RAS) based flood analysis results for SCS 100-year, 24 h design storms over the next 30 years. Land use changes in the basin mainly consist of gradual urbanization and densification from low to high intensity urban development by 2040. The models were calibrated and validated for past events and then run for future land use scenarios (2020, 2030, and 2040). The future land use scenarios were developed using GIS. Results demonstrate an appreciable increase in peak discharge and flood inundation extents for the future scenarios. From the baseline scenario to the 2040 scenario, for the different storms, there was a 10% to 19% increase in peak discharge, a 2% to 7% increase in water elevations, and a 5% to 8% increase in inundation area. A considerable reduction in peak discharges and inundation extents was achieved after the wetland area was increased to 6%, 8%, and 10% from the original 5% for the 2020, 2030, and 2040 scenarios, respectively. There was a 12% to 18% decrease in peak discharge, a 1% to 15% decrease in water elevations, and a 15% to 19% decrease in inundation area. This research demonstrates the importance of including wetlands in designing flood mitigation alternatives.

Integrated modelling for flood risk mitigation in Romania: case study of the Timis–Bega river basin

An integrated flood modelling approach has been applied in a demonstrator of a flood management system, which was developed within the framework of a collaborative project between Romania and the Netherlands. The developed demonstrator system had two objectives: (a) operational water management under extreme conditions when actions have to be taken quickly; (b) off-line analysis and design of flood mitigation measures and alternatives. This article presents the applied approach and the achieved results for meeting the second objective. The pilot basin for the development of the system was the Timis–Bega river basin, in which the rivers Timis and Bega were considered jointly. The system is based on modelling the flood generation and routing processes by combined development and application of hydrological and hydrodynamic models. The modelling system HEC-HMS was used for the hydrological model, HEC-RAS for the one-dimensional hydrodynamic model and SOBEK for the two-dimensional (2D) model used for downstream flood analysis and design of mitigation measures and alternatives. The 2D model includes alternatives of deliberate dike breaching as part of the analysis of the system response. The analysis presented is concentrated on a specific flood event that occurred in April 2005, which occurred due to dike breaches along the Timis river. The combination of models is first used for reconstruction of inundation patterns resulting during this flood event. Subsequently the models were used for testing flood mitigation alternatives of deliberate (planned) breaches of flood protection dikes located in the downstream part of the Timis river at the same location where they had occurred during the 2005 flood event, but at different times with respect to the arrival of the flood hydrograph. The demonstrated approach can enable decision-makers to analyse the behaviour of the physical system and design possible preventive and/or mitigation measures.

Structural master plan of flood mitigation measures

Abstract. Flood protection is one of the practical methods in damage reduction. Although it not possible to be completely protected from flood disaster but major part of damages can be reduced by mitigation plans. In this paper, the optimum flood mitigation master plan is determined by economic evaluation in trading off between the construction costs and expected value of damage reduction as the benefits. Size of the certain mitigation alternative is also be obtained by risk analysis by accepting possibility of flood overtopping. Different flood mitigation alternatives are investigated from various aspects in the Dez and Karun river floodplain areas as a case study in south west of IRAN. The results show that detention dam and flood diversion are the best alternatives of flood mitigation methods as well as enforcing the flood control purpose of upstream multipurpose reservoirs. Dyke and levees are not mostly justifiable because of negative impact on down stream by enhancing routed flood peak discharge magnitude and flood damages as well.

Integrating Multiple Perspectives in Social Multicriteria Evaluation of Flood-Mitigation Alternatives: The Case of Malborghetto-Valbruna

There is an increasing demand for a new paradigm to improve flood-mitigation decision processes that calls for risk-reduction strategies at several levels. This demand may gain ground only if dialogue is encouraged among different perspectives, disciplines, and knowledge types. The aim of this paper is to explore new methods to improve flood-mitigation decision processes. A growing body of evidence suggests that the involvement of the local actors is a key aspect in successful decision making. Following this premise, we analyze a recent case of controversy in flood mitigation in Malborghetto-Valbruna (Northern Italy), using social multicriteria evaluation (SMCE) and social actors' narrative analysis. Six alternatives are defined and the different positions adopted by the local actors are described. The different narratives of the actors are also analyzed to allow the identification of improvement routes for a more accurate SMCE of flood-mitigation alternatives. Thus, this case study suggests that the analysis of narratives is a useful tool to complement SMCE.

ASSESSING FLOOD MITIGATION ALTERNATIVES IN SHIJR AREA IN METROPOLITAN TAIPEI

The Keelung River Basin in northern Taiwan lies immediately upstream of the Taipei metropolitan area. The Shijr area is in the lower basin and is subject to frequent flooding. This work applies micromanagement and source control, including widely distributed infiltration and detention/ retention runoff retarding measures, in the Wudu watershed above Shijr. A method is also developed that combines a genetic algorithm and a rainfall runoff model to optimize the spatial distribution of runoff retarding facilities. Downstream of Wudu in the Shijr area, five dredging schemes are considered. If 10-year flood flows cannot be confined in the channel, then a levee embankment that corresponds to the respective runoff retarding scheme will be required. The minimum total cost is considered in the rule to select from the regional flood mitigation alternatives. The results of this study reveal that runoff retarding facilities installed in the upper and middle parts of the watershed are most effective in reducing the flood peak. Moreover, as the cost of acquiring land for the levee embankment increases, installing runoff retarding measures in the upper portion of the watershed becomes more economical.