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Levees aim to provide protection during floods, however, these structures can breach, causing significant damage. Flood maps that include levee breaching are often limited to deterministic methods. Where probabilistic breaching is done, it often requires computationally expensive Monte Carlo simulations and an understanding of the geotechnical levee properties that are often limited. In this paper, we combine existing fragility curves and empirical breaching equations with a framework for automating levee breaching in catchments with limited geotechnical information. This method can be adapted and applied to existing 2D flood models to determine the probability of inundation, given that a breach occurs. This ultimately allows for greater emergency responses and land use planning to reduce the flood risk faced by our communities. The method was applied to four case study catchments. The results showed that including levee breaching in one catchment led to an average increase in the inundated area by 48.2% and a tripling in the potentially exposed area. However, breaching in some locations reduced the inundation extent by 12%, illustrating the potential for fuse plug levees and floodways as a flood mitigation strategy. This strategy has seen successful usage internationally. Further investigation is recommended to consider whether these mitigation strategies should be enacted. [ABSTRACT FROM AUTHOR]

The Pitt Review of the 2007 summer floods in the UK, published in 2008, commended the potential of natural flood management (NFM) for reducing flood risk. NFM is a nature‐based approach that has since gained substantial interest from both practitioners and academics. The review further highlighted the need for catchment‐based flood management (CBFM) to enhance resilience to flooding and climate change by incorporating NFM and wider nature‐based solutions into hard flood protection systems. Such integrated approaches are considered to be more sustainable and adaptable than the traditional hard‐engineered measures. More recently, the European Commission's European Green Deal also highlighted the need for greater use of nature‐based solutions including NFM for managing flood risk. Whilst there have been many attempts to quantify the effects of NFM through hydraulic and hydrological modelling, there is still no systematic review conducted for these modelling works. This review aims to summarise the current NFM modelling approaches, as well as discussing their key limitations related to data, model methods, and real‐world applications. This paper then goes further to highlight potential solutions to some of these challenges and provides guidance to assist modellers to improve future modelling and data collection process. [ABSTRACT FROM AUTHOR]

Sea level rise (SLR) will affect water levels and increase flood risk in river deltas. To adapt river deltas to SLR, various strategies can be followed. Many urbanised river deltas already have flood protection in place. Continuing a protection strategy under an increasing SLR, would mean higher embankments along the coast and rivers and possibly closing off the river mouths from the sea. However, closing of rivers will hamper the river flow. How to adapt river deltas and enabling rivers to discharge into the sea is a challenging question. This paper assesses impacts of SLR on flood risks in the Rhine‐Meuse Delta in the Netherlands in case the current protection strategy is continued and explores two alternative protection strategies: (1) a closed system with pumps and discharge sluices and (2) an open system in which rivers are diverted to less densely populated areas. The second alternative results in a more flexible river delta, which can accommodate larger SLR. The paper shows that a systems approach and using quantitative assessments of the implications of strategies is possible. This is needed to further assess the adaptation options, so we can anticipate and adapt when needed and avoid regret of decisions. [ABSTRACT FROM AUTHOR]

Adaptations to flood‐proof individual properties (referred to here as property‐level adaptation, PLA) provide a potential means of reducing flood risk at isolated properties, whilst conventional community‐scale flood protection (CSFP) is usually more economical in protecting high‐density urban spaces. This paper develops a risk‐based framework to identify the tipping point when PLA measures become more cost‐beneficial when compared to CSFP in different urban densities. The framework was demonstrated using a hypothetical case study based on a residential area in Teddington, London. Sensitivity analysis was performed by varying the building densities in the urban space. Results show that PLA can have a role to supplement CSFP even in dense urban areas if the CSFP standard of protection is low. However, adding some element of CSFP to PLA can be more cost‐effective than implementing a single higher protection standard of PLA. Given the unique flood risk condition of most urban spaces, and the sensitivity of cost‐effectiveness of flood adaptation measures such as those demonstrated in this work, this approach can provide additional information to assist decisions in finding a sensible portfolio of measures that match that risk condition. [ABSTRACT FROM AUTHOR]

Snowmelt floods are highly hazardous meteorological disasters that can potentially threaten human lives and property. Hence, snowmelt susceptibility mapping (SSM) plays an important role in flood prevention systems and aids emergency responders and flood risk managers. In this paper, a method of identifying snowmelt flood hazards is proposed, and a large‐scale snowmelt flood hazard zonation scheme based on historical recordings and multisource remote sensing data is established. To assess the quality of our approach, the proposed model was tested in the cold and arid region of Xinjiang, China. Overall, 140 historical snowmelt flood events and 27 explanatory factors were selected to construct a geospatial dataset for SSM of the contemporary period. GridSearchCV was used to comprehensively search the candidate parameters from the grid of given parameters obtained with the random forest (RF) algorithm. Then, the geospatial dataset was divided into two subsets: 70% for training and 30% for testing. Next, SSM results were obtained with the RF algorithm using optimized parameters. The results indicate that our optimized RF classifier performs well for the task of SSM, with a high AUC value (0.975) for the test dataset. The validation and analysis suggest that the proposed method can efficiently identify snowmelt flood hazards in undersampled arid areas at a regional scale. [ABSTRACT FROM AUTHOR]

For several years, fragility curves have been used to assess the failure probability of flood defences when undertaking probabilistic flood risk assessments. When preparing an editorial, members of the Editorial Board sometimes discuss cases of floods that are topical at the time of writing. [Extracted from the article]

Urban development broadly impacts the hydrological cycle, leading to increased peak flow and flooding. Surface water detention ponds are among the most efficient measures for attenuating peak flow and returning it from development to pre‐development conditions. However, the major challenge is identifying optimal locations and cost‐effective designs for these ponds. This paper presents a new framework for identifying the best strategies for using detention ponds to control floods in urban drainage systems (UDS). The framework comprises a portfolio of simulation tools coupled with evolutionary optimisation and multi‐criteria decision analysis models. Hydraulic simulation of UDS is first modelled using SWMM and GIS tools. A multi‐objective optimisation model was used to find the optimal location and design for detention ponds. The compromise programming (CP) multi‐criteria decision‐making method was then used to prioritise potential best management solutions for detention ponds based on several sustainability criteria comprising economic, environmental, physiographic and social factors. The results identified the key features of potential detention ponds appearing in all multi‐objective optimal solutions that are useful for decision‐makers/designers when planning/designing for new detention ponds. The selected optimal pond strategies can significantly improve the UDS performance by decreasing flood damage between 66% and 90% at the cost of between $50,000 and $160,000. [ABSTRACT FROM AUTHOR]

Levees are the most frequently used flood protection measure worldwide. In central Europe, they have been built systematically since the beginning of the 19th century. After the extreme regional floods in 1997, 2002 and 2013, the need arose for a more systematic and optimised approach to levee design and management, including the decommissioning of ineffective dike reaches. In this paper, a multicriterial algorithm is presented for the optimisation of levee management. The aspects considered are flood risk, economy, technical conditions, environmental issues and the consistency with general documents and principles in water management. The method is demonstrated via a case study of a levee subsystem in the upper Morava River basin. [ABSTRACT FROM AUTHOR]

To address the two problems of unclear delineation of sub‐catchment and complicated and cumbersome parameter rate determination in the Storm Water Management Model (SWMM), this study proposes a rapid construction method of SWMM based on the principle of single urban functional area combined with K‐means clustering algorithm, The research area is the southern part of Jinshui District, Zhengzhou City. The Hydrological Response Unit (HRU) contains only a single urban functional area, divided by combining the natural and social attributes of the urban surface. Calibrated uncertain parameters from 76 papers were selected as samples, and the K‐means clustering algorithm was used to cluster and calculate the parameter values, to improve the SWMM model, selecting three typical rainfall runoff processes for validation application. The results show that simulated runoff is consistent with measured runoff trends, with the NSE and R2 value scores of the flow processes of the three floods above 0.86 and the, locations and numbers of flooded nodes are consistent with the actual research. This provides a new idea and technical support for the construction of urban flood models in flood prevention and mitigation. The relevant results can provide scientific decision‐making reference for urban flood forecasting and warning. [ABSTRACT FROM AUTHOR]

This paper presents a multireservoir flood control model that incorporates operating rules to alleviate the risk that results from traditional flood control models. The model is accurately reformulated into one that can be solved with the mixed integer linear programming (MILP) and approximated with a two‐stage linear programming (TSLP) to speed up the solution by excluding all the binary variables. A scroll decision‐making strategy is proposed by assuming only a few days of future inflows being predicted with certainty. With 10 historical and 30 designed floods in different magnitudes, the models and methods are applied to the Yangtze River basin, which includes 11 cascade reservoirs. The results on average show the MILP reduces the rule violation by 17%, while the TSLP is more than 150 times faster in CPU time. Excluding one of the reservoirs from the simulation reveals that the Three Gorges (TG) contributes the most in flood detention, accounting for 76% on average for once‐in‐a‐century floods. Interestingly, with the scroll decision‐making strategy implemented, the change from 3 to 7 days of certain forecasting has the most significant reduction in both the rule violation and flood detention, indicating that the forecasting accuracy of more recent inflows is more valuable for flood control. [ABSTRACT FROM AUTHOR]

This contribution presents an integrated method to inform future‐oriented flood risk management across policy domains at the scale of river sections and (sub)catchments. The RegioFEM (Regional Floodplain Evaluation Matrix) combines approaches from hydrology, hydraulic engineering, spatial planning and stakeholder engagement to assess the dynamic changes in floodplains in consideration of projected investments in flood protection, expected settlement and infrastructure development and the likely climate‐induced changes in flood runoff. In this paper, we present the step‐by‐step approach of the RegioFEM, outlining how the method can be applied and replicated in practice in support of catchment‐oriented and forward‐looking flood management policies. The RegioFEM builds on the understanding of floodplains as coupled human and natural systems. It supports the simple comparative evaluation of the expected impacts of future developments in riparian areas on flood risk change and thus provides a basis to anticipate reciprocal effects between flood defence and land development to improve the sectoral interplay of integrated flood policies. [ABSTRACT FROM AUTHOR]

Effective management of flood risks requires the prioritization of appropriate flood control solutions. This study aims to prioritize structural flood control options using multi‐criteria decision‐making (MCDM) methods. Four MCDM methods, namely analytic hierarchy process, technique for order preference by similarity to ideal solution, multi‐criteria optimization and compromise solution, and Fuzzy‐VIKOR are employed to assess and rank the flood control options based on multiple criteria. Field surveys, interviews with local authorities and experts, and on‐site assessments of existing flood control structures constituted the primary data collection methods. The findings demonstrate the effectiveness of reservoir dams, retention basins, and levees as viable solutions. Conversely, flood control gates and the no‐project options were assigned lower priorities. The findings highlight the importance of considering multiple MCDM methods to account for variations in rankings. The study provides valuable insights into the decision‐making process for prioritizing flood control options in the study area. These findings can assist policymakers and stakeholders in effectively allocating resources and implementing appropriate structural flood control measures to mitigate flood risks. [ABSTRACT FROM AUTHOR]

Coastal flood managers seek to anticipate future flood risk and as a result consider the adaptation of flood defences. Instead of crest heightening, dikes can be adapted to include hydrodynamic reducing vegetated foreshores to form a nature‐based hybrid flood defence, for instance; at managed realignments. In this study we investigated the potential of vegetated revetments as a natural continuous connection between the realigned dike and restored foreshore. We applied the historic grass sod transplantation technique with the aim to improve our understanding of the strength of a transplanted sod revetment. In Living Lab Hedwige‐Prosperpolder, dikes were available for in‐situ experiments during managed realignment preparations. We transplanted grass sods and studied erosion resistance after one growth season. Our results show transplanted sod vegetation continued to grow and started to attach to the clay layer. While erosion occurred under extreme wave impact and overflow, the sod pulling method revealed individual sod strength. In conclusion, sod transplantation is a good technique to source local material for green realigned dike revetments. A vegetated dike revetment can hereby create a natural continuous connection between the realigned dike and foreshore, which benefits flood protection as well as flora and fauna. [ABSTRACT FROM AUTHOR]

Accurate prediction of urban floods is regarded as one of the critical means to prevent urban floods and reduce the losses caused by floods. In this study, a refined prediction and early warning method system for urban flood and waterlogging processes based on deep learning methods is proposed. The spatial autocorrelation of rain and ponding points is analyzed by Moran's I (a common used statistic for spatial autocorrelation). For each ponding point, the relationship model between the rainfall process and ponding process is constructed based on different deep learning methods, and the results are analyzed and verified by mean absolute error (MAE), root mean square error (RMSE), Nash efficiency coefficient (NSE) and correlation coefficient (CC). The results show that the gradient boosting decision tree algorithm has the highest accuracy and efficiency (with a 0.001 m RMSE of the predicted and measured ponding depth) for ponding process prediction and is regarded as the most suitable method for ponding process prediction. Finally, the real‐time prediction and early warning of urban floods and waterlogging processes driven by rainfall forecast data are realized, and the results are verified by the measured data. The research results can provide theoretical support for urban flood prevention and control. [ABSTRACT FROM AUTHOR]

Camera surveillance systems can record urban waterlogging processes. Objects with regular shapes and fixed sizes captured by the camera can be utilized to calculate urban waterlogging depths based on geometric principles. In this study, we propose a machine learning‐based method to measure urban waterlogging depths using wheels and traffic buckets captured in video images as reference objects. This method is validated through laboratory experiments and observed data. The results demonstrate that: (1) the urban waterlogging depths calculated using urban reference objects show high consistency with the observed water level data; (2) in the laboratory scenario, the probability of error within 3 cm for measurements based on the hub, tire, and traffic bucket are 99.07%, 99.38%, and 81.55%, respectively; (3) in the real‐world scenario, the probability of error within 3 cm for measurements based on car hubs and pickup truck hubs are 97.30% and 95.14%, respectively. In conclusion, urban waterlogging depths can be accurately measured using reference objects with regular shapes. The proposed method can help obtain waterlogging data with higher temporal and spatial resolution at lower economic costs, which is of great significance for urban flood control. [ABSTRACT FROM AUTHOR]

Flood risks are increasing in Europe, and the EU Floods Directive is one of the main efforts to implement and harmonize effective flood risk governance and management among member states. At the same time, the ongoing shift from mere flood protection to multi‐functional flood risk governance calls for increased collaboration among a diversity of actors, typically with varying interests and responsibilities. In this study, we analyze the actor networks unfolding from flood risk management plans to visualize the diversity of roles and connections between actors participating in flood risk management measures. We introduce a new framework for analyzing flood risk management plans and related actor networks using Social Network Analysis and test it in the context of Finland. The framework helps to visualize the diversity of networks for different flood risk management strategies. The analysis also reveals the central roles that different types of actors—including those outside the public sector—occupy in the network. The findings suggest that Social Network Analysis can be used in the context of EU flood risk governance and that flood risk management plans offer an excellent opportunity for comparative governance studies in the EU. [ABSTRACT FROM AUTHOR]

In 2021, eight counties in Southeast Texas formed a non‐tax authority flood control partnership to provide a forum for communication, create a regional database and improve flood modeling, early warning, and flood mitigation decisions. This partnership is able to successfully deploy and manage an early warning flood system network at relatively low‐cost by: (i) assigning the university as technical expert and general network administrator so that no additional agency workforce is required to operate and maintain the system, (ii) the flood monitoring system is a simple system and (iii) the data was able to be displayed in real‐time using an existing web‐based dashboard owned and operated by another agency within the partnership. The low‐cost sensors are lightweight and easily mountable which allowed them to be rapidly deployed within a short period of time (73 sensor sites installed within 7‐month window) over a 6000 square mile area. The data is shared with the public, and local, state, and federal agencies to monitor drainage infrastructure, and provide the community with flash flood and roadway closure alerts. [ABSTRACT FROM AUTHOR]

Using an economic model of how river embankments affect local residents, we explore the efficiency of embankment construction from two viewpoints: (1) which section of a river should be constructed first, the upstream or downstream section, and (2) how tall the embankments should be constructed depending on the section. For this purpose, we first develop a model to determine efficient construction of embankments using a hydraulic model. Then, we perform numerical simulations, which are calibrated with recorded ground data for the Kitakami and Abukuma Rivers. The results reveal that the construction from the upstream section can be efficient if the upstream section has a much larger population than the downstream section. We show that constructing higher embankments in the upstream section generates negative externalities in the downstream section because it increases the possibility of flooding in the downstream section. In addition, when the amount of inflow from tributaries into the downstream section is sufficiently large compared to that into the upstream section, embankments with efficient heights bring about Pareto improvements, giving benefit to residents in the downstream section as well as the upstream section. Moreover, we show that the efficient embankment heights depend on which section the construction starts from. [ABSTRACT FROM AUTHOR]

Abstract Urban development broadly impacts the hydrological cycle, leading to increased peak flow and flooding. Surface water detention ponds are among the most efficient measures for attenuating peak flow and returning it from development to pre‐development conditions. However, the major challenge is identifying optimal locations and cost‐effective designs for these ponds. This paper presents a new framework for identifying the best strategies for using detention ponds to control floods in urban drainage systems (UDS). The framework comprises a portfolio of simulation tools coupled with evolutionary optimisation and multi‐criteria decision analysis models. Hydraulic simulation of UDS is first modelled using SWMM and GIS tools. A multi‐objective optimisation model was used to find the optimal location and design for detention ponds. The compromise programming (CP) multi‐criteria decision‐making method was then used to prioritise potential best management solutions for detention ponds based on several sustainability criteria comprising economic, environmental, physiographic and social factors. The results identified the key features of potential detention ponds appearing in all multi‐objective optimal solutions that are useful for decision‐makers/designers when planning/designing for new detention ponds. The selected optimal pond strategies can significantly improve the UDS performance by decreasing flood damage between 66% and 90% at the cost of between $50,000 and $160,000.

Accompanying its rapid urban development, prevalent urban flooding incidents have been occurring in China in the past two decades with increasing frequency. Through a comparison with generally accepted urban flooding management practices, we (the authors) identified that a lack of surface water runoff management considerations (i.e., missing a major drainage system in urban stormwater system) and inadequate local mitigation are the primary causes of urban flooding problems in China, which in turn is rooted in the planning stage of a city's development. Following identification of the primary causes for the problems, we propose the development of master drainage plans (MDPs) for the concerned cities or regions as the first effective step to mitigate the serious urban flooding problems facing many cities today. An MDP would provide necessary elements to develop a major drainage system for the city's stormwater system and allow for an accurate calculation of parameters necessary for installation of adequate local mitigations. Lessons learned in this study should be useful for China's administrative agencies and professionals while they try to find solutions to their urban flooding problems and beneficial to other nations facing rapid urban development in the future or with existing urban flooding threats. [ABSTRACT FROM AUTHOR]

The flood control ability of cascade reservoirs is affected by many factors, such as the inflow flood form, and flood control scheduling rules. When large cascade reservoirs were built, it is necessary to evaluate the overall flood control ability of the reservoirs and explore the best joint scheduling strategy. In this study, cascade reservoirs in the upper reaches of the Yangtze River in China were selected as the research case. A stochastic model of inflow floods and a dynamic capacity flood regulation model for the Three Gorges Reservoir (TGR) were established, and the most dangerous inflow floods for downstream flood control were generated. Different scheduling strategies for the cascade reservoirs were set to block the TGR inflow flood to explore the flood control risk in the Jingjiang area under joint operation of the TGR and the upstream cascade reservoirs. The research results show that the joint flood control scheduling strategy has a huge impact on the flood control ability of cascade reservoirs, and different scheduling schemes must be adopted according to the inflow flood characteristics of the reservoirs. This study provides a new idea for systematically evaluating the flood control ability of large cascade reservoirs and selecting appropriate scheduling strategies. [ABSTRACT FROM AUTHOR]

Abstract This paper presents a multireservoir flood control model that incorporates operating rules to alleviate the risk that results from traditional flood control models. The model is accurately reformulated into one that can be solved with the mixed integer linear programming (MILP) and approximated with a two‐stage linear programming (TSLP) to speed up the solution by excluding all the binary variables. A scroll decision‐making strategy is proposed by assuming only a few days of future inflows being predicted with certainty. With 10 historical and 30 designed floods in different magnitudes, the models and methods are applied to the Yangtze River basin, which includes 11 cascade reservoirs. The results on average show the MILP reduces the rule violation by 17%, while the TSLP is more than 150 times faster in CPU time. Excluding one of the reservoirs from the simulation reveals that the Three Gorges (TG) contributes the most in flood detention, accounting for 76% on average for once‐in‐a‐century floods. Interestingly, with the scroll decision‐making strategy implemented, the change from 3 to 7 days of certain forecasting has the most significant reduction in both the rule violation and flood detention, indicating that the forecasting accuracy of more recent inflows is more valuable for flood control.

Watershed characteristics are one of the crucial factors affecting watershed hydrologic processes. Watershed hydrologic process regulation has been shown to be an effective tool for flash flood management. This study aims to propose a coupling method to evaluate the flash flood hazard degree of small hilly ungauged watersheds based on their watershed characteristic factors and identify sensitive factors influencing flash flood hazard. In this regard, nine watershed characteristic factors were selected for flash flood hazard sensitivity analysis. The variable fuzzy method (VFM) was proposed to calculate the eigenvalue of flash flood hazard degree for each small hilly watershed, and mutual entropy was proposed to identify sensitive factors influencing hazard degree. As an example, the sensitive factors in Licheng County with 119 small hilly watersheds in China are identified and further verified by stepwise regression analysis, which are mean watershed slope, soil moisture, average width of the mainstream, and watershed shape factor. This study shows that VFM and mutual entropy can be used jointly to identify the sensitive factors associated with the flash flood hazard in small hilly ungauged watersheds. The results can be used for engineering measure management in flash flood hazard control. [ABSTRACT FROM AUTHOR]

This article analyzes residential property transactions to better understand the impact of urban flooding events and property distributions on the floodplain on real-estate markets. We studied patterns before and after major fluvial flooding events in three counties that experienced such events between 2009 and 2013: Benton County, Oregon; Boulder County, Colorado; and Cass County, North Dakota. We tested for the presence and distribution of price discounting before and following these flood events using a hedonic differencein-difference regression model. Floodplain discounts were detected in all three counties, over the full study period, including before and after flooding. However, only Boulder County exhibited a statistically significant price discount in the wake of the flooding event at the center of our analysis, with prices falling by 6.26% in the 100-year floodplain until they rebounded after approximately 2-3 years. In Benton County, we were not able to detect a post-flood price effect, but prices throughout the study period were 9.4% lower in the 100-year floodplain compared to comparable properties outside the floodplain. Cass County experienced weaker discounting and only in the 500-year floodplain, but a large flood control project was widely discussed after the 2009 flood event, which may have prevented widespread price discounting. The Boulder County case study confirms the phenomenon of post-flood real estate discounting and subsequent rebound, as documented by other researchers. The other two case studies, interestingly, document that such discounting is not universal. We suggest that the difference seems to be explained by differing levels of pre-flood local flood-risk awareness, along with the magnitude of the triggering flood event. The new availability of nationwide real-estate data allows for new and more detailed assessment of these important distinctions. [ABSTRACT FROM AUTHOR]

Flooding is New Zealand's most frequent natural hazard, responsible for the highest number of declared civil defence emergencies and greatest regular economic loss. Stopbanks (levees) perform a critical flood protection function in all regions of the country. However, there have been limited and inconsistent records on the location and physical attributes of these stopbanks at a national level. Through collaboration with regional government representatives, we provide the first standardised national inventory of stopbanks, the New Zealand Inventory of Stopbanks (NZIS). The NZIS provides a standardised geospatial overview of New Zealand's 5284 km long stopbank network, enabling spatial reviews and comparisons of flood protection characteristics at national and regional scales. Around 64% of New Zealand's total stopbank length is situated within five regions (Canterbury, Waikato, Southland, Manawatu-Whanganui and Bay of Plenty), while the nation's most densely population region, Auckland, accounts for just 1.9% of the total national stopbank length. Our research uses the NZIS geospatial dataset to conduct a preliminary exposure assessment of New Zealand's stopbank network to seismic and co-seismic hazards; including proximity to known active earthquake faults, ground shaking intensities and susceptibility to liquefaction and landslides. Preliminary exposure assessments provide an example of how the NZIS can be adopted and applied. [ABSTRACT FROM AUTHOR]

An increase in heavy precipitation associated with climate change has exacerbated flooding in the Eastern U.S. To assess regional flood risk with changing climatic conditions, we demonstrate the application of a novel hydrologic modeling framework that integrates climate projections with a coupled Noah‐MP land surface model and a two‐dimensional HEC‐RAS hydrodynamic model. We employ this framework along a 41 km reach of the Susquehanna River near Harrisburg, Pennsylvania, where recent flood damages exceeded $2 billion (2011 Irene and Lee floods). Historical and future 30‐year and 100‐year peak‐discharge estimates were compared to assess how flood risk might be altered due to climate change. Results indicate that precipitation increases from climate change do not always lead to increases in flood risk, because interplay of hydrological components in the watershed, which are considered by Noah‐MP, largely controls flooding severity. However, climate change is expected to increase the severity of extreme events; if a 50‐year flood (the recurrence interval of Tropical Storm Lee) occurred toward the end of the 21st century in the worst‐case emission scenario, then flood volume would increase by 40% and flood extent by 15%, due to an increase in soil moisture from a wetter overall climate. [ABSTRACT FROM AUTHOR]

Flood risk managers face increasing challenges in anticipating future developments and coordinating flood risk management on a regional level. The regional floodplain evaluation matrix (RegioFEM), a method to support a future‐oriented flood risk management at a regional scale, was applied in a section of the Raab River in Austria. The developed method uses several parameters assessing the consequences of changes in the study area, which lead to changes in flood risk. Settlement development, planned flood protection measures and the likely increase of flood runoff due to climatic changes are considered. Parameters include hydrological (e.g., peak reduction), hydraulic (inundation area), spatial (affected buildings) and monetary (damage potential) ones. The results of the application of the RegioFEM were presented at a regional expert workshop, conducted to gain feedback about the possibilities and limitations of implementing the method into practice. Considering future changes and evaluating their impacts on flood risk can provide stakeholders and decision makers valuable information for sustainable flood risk management. [ABSTRACT FROM AUTHOR]

Plants, especially trees, provide ecological functions but may harm the flood conveyance efficiency of rivers. Understanding the impacts of tree heights, tree areas, and tree locations on flood levels is crucial for floodplain management. This study aims to present a methodology to improve the performance of hydrodynamic modeling by considering plant resistance with the goal of analyzing flood risk reduction strategies that support ecological conservation enhancement. An unmanned aerial vehicle was used to collect floodplain topography, landcover, and tree characteristic data. A modified maximum likelihood classification scheme was developed by incorporating the tree height information to improve the landcover classification. The water‐blocking effect of trees, which represents the reduced flood conveyance area, was investigated by establishing tree obstructions in hydrodynamic models. Two hydrodynamic models were established with different tree obstruction setups and Manning's n values, including blocked obstructions (BOs) and conventional high n‐values (Adj‐n). Among the model setups, the Manning's n values of the trees remained the same as that of the soil in the BO model, in which trees were modeled as blocking obstructions. The n‐values of trees were determined to be 0.022 in the BO model and refined to 0.055 in the Adj‐n model after the model calibration and verification processes. The results indicated that the simulated flood levels of the BO model were very similar to those of the Adj‐n model. The NSE values were 0.98 and 0.97 in the simulations of two historical typhoon events, indicating that the BO model could obtain reliable predictions without altering the n‐values. The verified BO model was used to evaluate the degrees of influence of tree heights, tree coverage areas, and tree locations on flood levels. Several nature‐based solutions were proposed to analyze the tradeoffs between reducing flood prevention and enhancing wetland restoration using the verified BO model, suggesting a win–win strategy for natural river management. [ABSTRACT FROM AUTHOR]

Multireservoir joint flood control operation is an important nonstructural measure for flood control in some basins. Owing to the existence of uncertainties in flood control operation, various degrees of risk can be shown in flood control operation systems. Examining these uncertainties and the resulting risk of failure in multireservoir operation systems is extremely beneficial and indispensable for basin flood mitigation. In this study, different stochastic simulation methods were employed to generate streamflow series at multiple stations and other uncertainties such as the flood forecast errors, discharge capacity, and reservoir storage. Then, the Monte Carlo framework was established based on the simulation sequence to estimate the risk of a failure of each flood control unit in the flood control system. Furthermore, a comprehensive risk assessment indicator was proposed to consider the failure probability and failure consequences at the same time. The Xiluodu‐Xiangjiaba‐Three Gorges cascade reservoirs were selected as a case study. Results show that the applied probabilistic simulation methods could simulate various uncertainties in a multireservoir flood control system effectively, and the proposed risk analysis method could comprehensively evaluate the risks of reservoir overtopping, flood flows exceeding a standard, and flood diversion from the perspective of overall watershed security. [ABSTRACT FROM AUTHOR]

A major flood management project that integrated these approaches into the design was the Maidenhead Windsor and Eton flood alleviation scheme constructed in the 1990's at a cost exceeding £80 M. The response to this coastal flood, and the earlier widespread and exceptional river flooding in England of 1947, was the implementation of many engineered flood defence schemes in the 1950's and 1960's culminating with the construction of the Thames Barrier in 1984. I mainly concentrate on examples from river flood risk but natural approaches to coastal flood management are discussed in some of the documents referenced here. This document describes NFM as: the process within sustainable flood management which applies traditional land management techniques to address the causes of the flooding problem rather than trying to protect the impacted site. [Extracted from the article]