Hasil untuk "River protective works. Regulation. Flood control"

Samuel E. Munoz, Liviu Giosan, Matthew D. Therrell et al.

Linda Speight, Elizabeth Stephens, Laurence Hawker et al.

Abstract International humanitarian organisations increasingly turn to forecast teams to support the coordination of efforts to respond to disasters caused by hazards such as tropical cyclones and large‐scale fluvial floods. Such disasters often occur where there is limited local capacity or information available to support decision making and so global forecasting capacity is utilised to provide impact‐based flood forecast bulletins. A multidisciplinary team joined together to provide forecast bulletins and expertise for such events through the UK Foreign and Commonwealth Development Office (FCDO). This paper captures the successes and challenges from two cyclones: Hurricane Iota in Central America (November 2020) and Cyclone Eloise in Mozambique (January 2021). Recommendations to improve global forecasting systems are made which will benefit the international community of researchers and practitioners involved in disaster prediction, anticipatory action and response. These include the need for additional data and expertise to support the interpretation of global models, clear documentation to support decision makers faced with multiple sources of information, and the development of user relevant metrics to assess the skill of global models. We discuss the value of effective partnerships and improving synergies between global models and local contexts, highlighting how global forecasting can help build local forecasting capability.

David A. Dawson, Emily O'Donnell, Stephanie Bond et al.

ABSTRACT Urban Flood Risk Management (FRM) is a critical aspect of developing resilient environments for future generations to inhabit. It is now interconnected with the requirement to be more environmentally conscious through blue‐green infrastructure and the delivery of wider co‐benefits. The complexity of balancing urban growth with environmental drivers and increasing resilience is a key challenge for strategic urban decision‐making. Through computational modelling developments, new approaches to assess the spatial contribution of area to flood hazard are improving our understanding of the catchment response and our ability to develop multifunctional, multi‐beneficial projects. Yet at present, these approaches remain largely theoretical or are a ‘best intention’. This study uses an adapted ‘Unit Flood Response’ approach to generate Flood Source Area (FSA) maps for an urban catchment in the UK. A user‐focused engagement approach is applied using FSA outputs to generate key insight into its applicability from a practitioner perspective. The FSA modelling identified several hazard sources, from widespread contributions upstream to discrete contributions downstream. Stakeholders concluded that the FSA can support FRM at the pre‐planning stage by providing a clearer strategic vision across the catchment to support traditional ‘receptor‐led’ decision‐making. Improved identification and negotiation of project partners and the potential to support/identify wider scale options that integrate with existing and planned infrastructure in other sectors, for example, housing and transport, were additional benefits of this approach. While the computational aspects of FSA analyses could be improved for model robustness (e.g., calibration, validation), they must do so with a full understanding of the practicalities of applying these techniques on the ground, demonstrating the importance of co‐development of research with practitioners and decision‐makers.

Stephen Grey, Michael Turnbull, Jeffrey Simmons

Abstract A storm surge model has been developed as part of a pilot study for The Commonwealth of the Bahamas. The hydrodynamic model, TELEMAC‐2D, is used to simulate the response of water level to tide and the wind and atmospheric pressure fields of hurricanes and subsequent inundation over land. The model is used by The Bahamas Department of Meteorology to forecast storm surge and flooding over the islands of Grand Bahama and Eleuthera for incoming hurricanes to assist in preparation for and management of hurricane surge events and has been used in a flood risk assessment, reported in a companion paper. The model has been optimised to run quickly while also resolving the bathymetry and topography that affect the development and propagation of storm surge. Wind fields are generated within TELEMAC‐2D based on hurricane warning bulletins. The model has been validated for its representation of water level and against tide gauge measurements during four historical hurricanes: Irene, Sandy, Matthew and Dorian. Factors contributing to uncertainty in forecast predictions are discussed and recommendations are provided to improve the performance in future. The pilot study provides a template for future expansion to cover the other inhabited islands of The Bahamas.

Md Mostafizur Rahman, Kamrun Nahar Tanni, Ifta Alam Shobuj et al.

ABSTRACT Bangladesh is a flood‐prone country, yet studies on multidimensional vulnerability assessments related to floods remain limited. This study evaluates social, economic, physical, institutional, attitudinal, and gender vulnerabilities in Paschim Machimpur and Purba Machimpur, two rural flood‐prone areas in Sunamganj District. Primary data were collected from 487 households through structured questionnaires and face‐to‐face interviews. The data were analyzed using descriptive statistics, chi‐square tests, the Mann–Whitney U‐test, and a composite vulnerability index. The analysis reveals disparities in household characteristics, including size, age, education, and the presence of vulnerable members such as children and older people. Economic assessments show high dependency on agriculture and fishing, with many households lacking defined income sources and flood insurance. Physical vulnerabilities include poor housing materials and inadequate sanitation. Institutional vulnerabilities highlight deficiencies in early warning systems and flood preparedness. Attitudinal assessments reveal a lack of confidence in authorities' flood risk reduction programs, and gender vulnerabilities show women are disproportionately affected due to social and cultural factors. Despite similar overall vulnerability scores between the two areas, Paschim Machimpur shows higher composite vulnerability. The study calls for enhanced community engagement, better communication of flood risks, and the development of more robust early warning systems to reduce flood vulnerabilities.

Amrie Singh, Harry Mansfield, Maria Pregnolato et al.

ABSTRACT Subgrid sampling (SGS) has been increasingly integrated into hydraulic modelling to refine terrain representation without excessively increasing computational demands. This study investigates the effects of SGS and nature‐based solutions (NbS), focusing on flow velocities, storage volumes and mass balance stability. Using a rain‐on‐grid TUFLOW model, we simulate a 1‐in‐30‐year flood event across different NbS interventions, including leaky dams, floodplain planting and bunds with floodable depressions. Results demonstrate that higher SGS frequencies of 11 significantly enhance terrain resolution, improving the representation of flow paths and floodplain activation. However, a lower SGS frequency of three introduces notable numerical artefacts, leading to persistent negative cumulative volume errors and misrepresenting water retention within the system. NbS interventions generally minimise peak flow rates, with bunds and depressions (Option 3) proving the most effective, achieving a storage volume increase of up to 162.83% compared to the baseline scenario. Mass balance assessments show that models without SGS overestimate flood storage, potentially misguiding NbS implementation and compliance with flood storage regulations such as the UK Reservoirs Act (1975).

Salvatore Molica, Giuseppina Brigandì, Giuseppe Tito Aronica

ABSTRACT In this paper, a procedure for evaluating and comparing the efficiency between hard and soft flood risk mitigation measures in a highly urbanized area is presented. The European Directive 2007/60/EC promotes, in fact, the implementation of soft measures, which reduce the vulnerability of elements in exposed areas as a risk mitigation strategy and may be less expensive than classic defense measures and sometimes even more effective, but this aspect deserves further investigation. For these reasons, the effectiveness of these hard and soft measures has been here investigated in terms of average annual reduction in expected damage and subsequently through the application of a cost–benefit analysis. The effectiveness of these measures was calculated on a microscale by considering the lifetime of each measure. On the other hand, the efficiency comparison between the different scenarios was carried out at the meso scale, calculating the overall damage reduction for each scenario as the sum of the small contributions of the microscale analysis. The methodology was applied to the case study of the city of Barcellona located within the Longano catchment in the northeastern part of Sicily, Italy. Results showed how the use of soft measures can offer greater efficiency than the use of classical hard defense measures, both in terms of damage reduction and in terms of less time to return from the initial investment.

Xiangfen Liu, Junqi Yu, Yahua Li et al.

Plant growth-promoting rhizobacteria (PGPR) are used to assist phytoremediation. Synthetic PGPR can adapt to diverse sediment environments more effectively than single PGPR. However, their mechanisms of application in submerged macrophytes remediation of cadmium polluted sediment remains challenging. Here, we investigated the effect of synthetic PGPR on enhancing phytoremediation in cadmium polluted sediment and the underlying mechanisms promoting growth of submerged macrophytes. We conducted a comparison regarding the phytoremediation efficiencies of submerged macrophytes within cadmium polluted sediment under the conditions of the absence of PGPR, single PGPR and synthetic PGPR inoculation. The results indicated that the lower concentration of cadmium in the sediment was achieved under synthetic PGPR inoculation of two treatments, specifically decreased by 26.18 % and 25.55 %, because of the highest biota-sediment accumulation factor. Synthetic PGPR induced 44 %–88 % increase in the biomass of submerged macrophytes by regulating enzyme activities and photosynthesis system compared with the treatment with cadmium pollution only. The PGPR promoted significant increase of chlorophyll, the optimal/maximal quantum yield of PSⅡ (Fv/Fm) and carotenoids content with the highest increases in macrophytes inoculated with synthetic PGPR. Compared with the treatments inoculated with single PGPR, synthetic PGPR enhanced the activities of antioxidant enzymes to assist submerged macrophytes in resisting cadmium stress. Consequently, synthetic PGPR promoted the growth and cadmium accumulation of submerged macrophytes. Our research further observed that the translocation factor of the submerged macrophytes was below 1, showing that cadmium was not easily transferred within the macrophytes. Our study provides new perspectives into strategy development in microbe-assisted submerged macrophytes remediation of cadmium polluted sediment.

Pu Li, Kaiheng Hu, Lan Ning

Erosion of landslide dams by a natural debris flow as it travels down a sloping channel can dramatically increase flow size and destructive potential. Most research on the erosion of landslide dams focuses on those newly formed due to recent earthquakes or heavy rainfall. In this study, the debris-flow erosion of so-called highly-consolidated landslide dams (HCLDs) that are typically remnants of ancient earthquakes or rainfall events is investigated by using satellite image interpretation, field measurements, and mechanism analysis. Several HCLDs were identified in two catchments in Zhouqu and Ganluo counties in Gansu and Sichuan province, China, where two high-magnitude debris-flow events occurred in 2010 and 2020, respectively. The existence of HCLDs resulting in wide and narrow reaches alternatively alters the boundary conditions of debris flows and significantly affects the flow erosion and deposition processes. It is observed that the flow discharge increased notably after passing through or during narrowing sections of the channels and the estimated discharge amplification coefficients are approximately 3.3 and 2.7, respectively. The two cases demonstrate that rapid erosion through narrowing sections and subsequent headward erosion play a key role in the debris-flow volume growth by eroding HCLDs. Additionally, other mechanisms such as deposition of erodible material upstream of the dam, localized vortexes in converging and diverging sections, and collisional stresses within the debris flows can further contribute to the erosion of HCLDs and the amplification of debris-flow magnitude. Recognizing these hazardous effects of HCLDs on increasing debris-flow volume is helpful for making non-structural and engineering countermeasures against similar debris flow disasters.

Laxmi Prasad Devkota, Utsav Bhattarai, Rohini Devkota et al.

Abstract Accurate estimation of design floods is necessary for developing effective flood‐management strategies. Climate change (CC) studies on floods generally consider alterations in mean runoff using ensembles compared to a base period. In this study, we examined the plausibility and implications of applying individual climate model‐generated flows versus their ensembles to estimate peak floods (magnitude and timing of occurrence), using Budhigandaki River Basin of Nepal as a case study. Annual maximum one‐day floods were derived for four future climate scenario projections (cold‐dry, cold‐wet, warm‐wet, and warm‐dry) from simulated daily flow series. Future floods of six return periods estimated for the individual climate scenarios were compared with their “Ensemble” (combiner for the ensemble series is the arithmetic mean of daily floods), “Average,” and ‘Baseline.” Results showed that magnitudes of the flood peaks are such that those estimated using “Ensemble” < “Average” < individual series. We conclude that ensemble series should not be used for flood estimation because of the averaging effect. Designers should consider at the least the “Average” instead of the “Ensemble” series while designing climate‐resilient flood structures. Furthermore, the occurrences of flood peaks are likely to be confined within the monsoon season for the “Ensemble” but spread out in the other months for the individual climate scenarios. This could have direct implications on the availability and mobilization of resources as well as the need for a year‐round operational early warning system for flood risk management.

Björn Arvidsson, Jonas Johansson

Abstract Floods are destructive to society. Hence, to assess and manage flood risk is imperative. Flood risk assessments require several layers of analysis, from flood hazard to societal impact. This paper explores the maturity level and challenges related to three components of a comprehensive risk assessment: flood hazard, direct consequences, and indirect consequences. This is achieved by introducing and applying a maturity framework on flood hazard reports and flood risk management plans in Sweden, as required by the EU Floods Directive (FD). A longitudinal analysis is conducted over two FD cycles (2009–2015 and 2016–2021). Complementary interviews with county administrative boards and responsible authorities provide deeper insights into processes and practical challenges. The results reveal that the maturity level of flood hazard assessment is high, while direct and, in particular, indirect consequences assessments need increased attention and substantial improvements. Further, there is no significant increase in maturity between the FD cycles, indicating fundamental challenges towards achieving this. Critical steps forward include developing applicable methods for analysing both direct and indirect consequences of floods, improving data availability on functionality and interdependency of critical infrastructure and society at large, and creating incentives for a broader range of societal actors to participate in flood risk management.

Yihong Zhou, Zening Wu, Mengmeng Jiang et al.

Abstract 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.

مهتاب صفری شاد, محمود حبیب نژاد روشن, کریم سلیمانی et al.

بسیاری از مشکلات زیست ­محیطی، ناشی از تغییرات مولفه‌های اصلی چرخه هیدرولوژیکی است. با این ‌حال، مدلسازی بیلان آب می‌­تواند به درک بهتر از اجزای چرخه هیدرولوژیکی به‌منظور توسعه گزینه‌­های مدیریتی مناسب، کمک کند. هدف پژوهش حاضر، محاسبه سه مولفه مهم بیلان آب سطحی با استفاده از مدل WetSpass و ارزیابی این مدل در حوزه آبخیز همدان، بهار واقع در استان همدان در مقیاس زمانی ماهانه است. با توجه به اهمیت تبخیر و تعرق در محاسبات بیلان آب، نقشه­‌های تبخیر و تعرق خروجی مدل به تفکیک کاربری­‌های مختلف ارزیابی شدند. ارزیابی تغذیه آب زیرزمینی نیز با توجه به محاسبات دستی این متغیر برای سال 92-1391، انجام شد. سپس، نتایج ضریب همبستگی کرامر بین نقشه‌­های توزیع مکانی رواناب، تبخیر و تعرق واقعی و تغذیه آب زیرزمینی، با نقشه­‌های ورودی به مدل بررسی شد. به‌طورکلی، نتایج ارزیابی مدل در این تحقیق نشان داد، ضریب تبیین میان رواناب مشاهداتی و شبیه‌سازی‌شده در دوره واسنجی و اعتبارسنجی به‌­ترتیب برابر با 0.79 و 0.83 است. نتایج ارزیابی نقشه‌­های تبخیر و تعرق خروجی مدل WetSpass، قابلیت مدل را در شبیه‌­سازی رواناب، تبخیر و تعرق و تغذیه آب زیرزمینی با دقت قابل قبول تایید کرد. نتایج، حاکی از وجود ضریب همبستگی بالا بین مولفه تبخیر و تعرق با کاربری اراضی (0.54)، بافت خاک (0.45)، پتانسیل تبخیر و تعرق (0.42) و درجه حرارت (0.31) است. همچنین، نتایج نشان داد بین مولفه رواناب با کاربری اراضی (0.62) و بافت خاک (0.58) همبستگی بالا و بین مولفه تغذیه آب زیرزمینی با کاربری اراضی (0.32) و بافت خاک (0.34) همبستگی متوسط وجود دارد. بنابراین، کاربری اراضی و بافت خاک به‌­ترتیب اولین و دومین عامل تاثیرگذار بر توزیع مولفه‌­های بیلان سطحی بودند.

Taisei Koma, Tatsuhito Kono, So Kazama

Abstract 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.

Lei Ye, Fanzhang Zeng, Sifan Jin et al.

Abstract Recent years have witnessed great losses caused by floods due to the unknown of rivers’ flood conveyance capacities, which make it difficult for floods management. In particular, flood conveyance capacities of small and medium-sized rivers are usually designed to meet the flood with a return period of 10 years but these rivers have not been paid enough attention. After years of scouring and siltation, the flood conveyance capacities of the rivers are unknown, and flood disasters caused by reservoir discharge are unpredictable. The aim of this research is to set a standardized research process to find out the actual flood conveyance capacities of small and medium-sized rivers. The hydrodynamic model is constructed and calibrated to evaluate the river’s flood conveyance capacity. The design flood data are used to make the simulation, and the flood conveyance capacity of the river channel is evaluated combined with the actual situation of the river. Then with water level observation points settled, the dynamic process of water level of the river channel can be grasped and real-time assessment of flood risk of the river can be done. Taking the downstream of Yingna River, a typical small and medium-sized river flowing into the ocean, as an example, the results showed that this standardized process can provide a reference for the analysis of flood conveyance capacity of small and medium-sized rivers.

Anna Serra‐Llobet, Rémy Tourment, Antonin Montané et al.

Abstract Although hydraulic infrastructure such as levees remain important for flood risk management in the USA, France, and Quebec (Canada), there is increasing emphasis on nonstructural measures, such as regulatory flood maps, to reduce exposure and vulnerability, for example, preventing people from building in high hazard areas. One key concept related to areas protected by levees is that of “residual risk”, that is, the risk from floods greater than the design standard of the levees (levee overtopping) and from levee breach. In this article, we review the legislative framework for regulatory flood maps in the USA, France, and Quebec (Canada) and compare how residual risk behind protective structures is taken into account (or not) in regulatory flood maps. We find big differences in how the USA, France and Canada manage residual risk behind the levees. While in France the area behind levees is part of the regulatory flood prone area, and land use restrictions, building codes, emergency measures and risk communication are mandatory, in the USA the area behind levees is only shown as part of the regulatory flood prone area if the levee is not accredited. In Quebec, regulatory flood maps in general follow the French approach with a few exceptions.

Matthijs R. A. Gensen, Jord J. Warmink, Fredrik Huthoff et al.

Abstract In bifurcating rivers, an intervention aimed at flood risk reduction may trigger a change in discharge distribution and thus influence water levels throughout the entire river system. This article aims at assessing the impact of interventions on system‐wide water levels, explicitly accounting for a range of discharges and model parameter uncertainty. An idealized 1D model with dimensions of the bifurcating Dutch Rhine River is used. The results show that an unwanted increase in water levels downstream of the intervention occurs due to an increased discharge if a single intervention is implemented in a distributary. This effect can be counteracted by implementing a second intervention that balances the hydraulic effect of the first intervention at the bifurcation. However, unwanted water level increases still occur at other discharges. Furthermore, while interventions may reduce local water‐level‐uncertainty, it appears that uncertainty in discharge distribution is not reduced. This implies that flooding probabilities cannot be reduced throughout the entire river system by the implementation of interventions in upstream reaches. Concluding, for intervention design in a bifurcating river, it is important to consider the entire river system and explicitly account for a range of discharge conditions to avoid unwanted water level increases throughout the river system.

Peng Chen, Shuo Zhang, Jianhua Bao et al.

Abstract Frequent water‐logging disasters in cities are serious threats to urban residents. When a water‐logging disaster occurs, it is essential for residents to evacuate, taking refuge to reduce losses and to ensure safety. This project studied evacuation difficulty for residents in the Daoli District of Harbin during storm water‐logging. Starting from external factors and internal factors influencing resident evacuation, the study screened indicators for assessing the difficulty of evacuation during urban rainstorm water‐logging, constructed an evaluation index system and evaluation models to assess the difficulty of evacuation of residents. Results showed that residents in the vicinity of the three streets, Xinyang Road and Minqing Street, Zhaolin Street and Anfeng Street in the study area have difficulty in evacuation in the case of a 5‐year torrential rain disaster. Other areas had little impact. In a 100‐year torrential rain situation, it is more difficult for residents in Stone Road Bridge, the intersection of Market Street and Toulong Street, the intersection of Touloing Street and Zhaolin Street, the intersection of Anfa Street and JingweiErdao Street, and Anguo Street, while other areas were not seriously affected. The research results can provide new ideas for the study of evacuation of residents during urban water‐logging, and can also provide decision‐making basis for disaster prevention and mitigation for urban emergency departments.

Chiara Arrighi, Andrea Carraresi, Fabio Castelli

Abstract Cultural heritage (CH) is threatened by floods; however, the understanding of exposure and vulnerability is challenging and makes risk and resilience assessment rarely practiced. CH is crucial for post‐disaster resilience, especially when the local economy is based on tourism. The work presents a novel framework for evaluating flood resilience, indirect impacts, and associated risk in art cities. The exposure of CH is estimated using the number of visitors as a proxy variable for the social appreciation. A new depth‐idleness vulnerability function assigning a reopening time to flood depth is developed from post‐event reports. A resilience model is conceived to (i) describe the recovery dynamics, (ii) estimate the indirect impacts in terms of lost visitors to CH for different probabilistic scenarios, (iii) calculate risk, and (iv) identify mitigation actions. The application of the model to the art city of Florence (Italy), a UNESCO site visited by approximately 10 million people a year, shows that a medium recurrence interval flood requires a recovery time of 351 days and causes a loss of 10.5 million visitors. The annual average number of lost visitors is 88,000 approximately. Resilience can be increased by accelerating the reopening and by reinforcing the attractivity of the city.

Yichen Yao, Caihong Hu, Chengshuai Liu et al.

Abstract Climate change and rapid urbanization have increased pressure on drainage systems, posing new challenges to preventing and controlling urban waterlogging. In 2013, China proposed the Sponge City, a strategic measure for urban waterlogging control. This study quantifies the effects of stormwater management measures in runoff reduction for different levels of rainfall and conducts a one‐dimensional visual analysis of urban waterlogging risks. At the same time, the best cost‐effective scheme is determined based on life‐cycle cost, analytic hierarchy process, and regret decision theory. The results showed stormwater management measures could realize the function of runoff control and waterlogging prevention, especially under low precipitation. However, these measures were still not enough to eliminate waterlogging risk. Combined measures have stronger runoff control capabilities than single measures. Considering economic, environmental, and operational impacts comprehensively, the combined measures of bio‐retention (BR), permeable pavement (PP), and green roof (GR) were determined as the best cost‐effective scheme because of the lowest regret value. The proposed method is helpful to provide reference and decision‐making basis for the construction of sponge cities in the future.