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

Afsheen Fatima

Zekai Li, Kaihua Guo, Huanfeng Duan et al.

ABSTRACT Physics‐based flood hydrodynamic models are widely used for predicting inundation in urban basins with complex building layouts. While the treatment of urban buildings in these models has been extensively discussed, over‐assumptions can introduce inaccuracies, uncertainties, and excessive computational effort, particularly under data‐scarce conditions. This study proposes a simple yet effective method, the Building Coverage Ratio (BCR) scheme, to account for building effects in city‐scale urban inundation modeling. The BCR scheme quantifies water abstraction to generate surface runoffs in densely built‐up areas by dynamically adjusting drainage and infiltration volumes based on the proportion of building footprint in each grid cell. This approach improves the accuracy of urban flood predictions when high‐resolution data is unavailable. Validated against a historical rainstorm event in Zhuhai, China, the BCR scheme demonstrated its capability to efficiently and accurately reproduce spatiotemporal inundation patterns. The method significantly improved street‐level flooding simulations, which are often underestimated in traditional approaches that neglect building effects. Results show that simulation accuracy increases from 33% without treatment to over 85% when the BCR scheme was applied to 30 m‐resolution Digital Elevation Model (DEM). As the method relies entirely on open‐source datasets, it offers a practical and transferable solution for urban flood prediction in data‐scarce regions.

Minghui Shen, Chunhong Hu, Shuai Guo et al.

The Three Gorges Project (TGP) plays a pivotal role in flood control, power generation, and water resource management along the Yangtze River. Nevertheless, its construction and operation have profoundly altered the downstream suspended sediment regime, reshaping the complexity of sediment transport processes. However, traditional studies often rely on single-parameter analyses, failing to provide a holistic view of the system’s complexity and the nonlinear, interactive nature of downstream recovery. To quantify these changes, we applied multiscale entropy (MSE) analysis to daily suspended sediment load records (1992–2023) from eight mainstream gauging stations. The results revealed a spatially heterogeneous response: In the near-dam sections (Yichang, Zhicheng, and Shashi), the complexity of the suspended sediment dynamics decreased while the sequence similarity increased, whereas in the middle and lower reaches (Jianli, Luoshan, Hankou, Jiujiang, and Datong), the complexity increased and the uniformity decreased. On the basis of a process understanding and empirical observation of the system, we have established a functional framework HSF = f ((Var(Q), Var(SSC), φtrib; ηprot) to mechanically explain these comparative reactions. Specifically, (1) flow regulation by the TGP compresses daily discharge variability (↓Var(Q)), suppressing extreme events and reducing complexity; (2) sediment trapping narrows the range of suspended sediment concentration (↓Var(SSC)), further enhancing uniformity; (3) tributary and lake inputs (↑ φtrib) introduce temporally variable and compositionally diverse sediments, increasing stochasticity and complexity; and (4) bank and bed protection (↑ ηprot) restricts local sediment supply, contributing to homogenization. The interplay of these drivers produces a dual-response pattern—simplification in near-dam reaches versus diversification in far-dam reaches—highlights the spatial heterogeneity of dam-induced impacts. By explicitly linking entropy metrics to physical drivers, this study provides not only a diagnostic tool for characterizing sediment dynamics but also a mechanistic understanding of how large dams restructure riverine processes. These insights offer a theoretical basis for more targeted sediment management strategies in regulated river systems.

Karen Potter, Sarah Fitton

ABSTRACT Across the last decade ‘resilience’ has become a guiding principle for flood risk management (FRM) policymakers. The importance of the role of communities has been recognised, and there is a growing emphasis on innovation to contend with the complexity in community resilience building. Problematic traditional approaches and norms of risk authorities and other stakeholders need to be tackled to bring about meaningful change across social relationships and existing behaviours through social innovation. The paper presents an exploratory case study: Project Groundwater, a partnership building community resilience to groundwater flooding. Following interviews with Project Groundwater partners, we suggest that social innovation was largely ‘hidden’ from view. This paper uses a ‘communication continuum’ to set out the project's communication journey, making visible the processes and practices lying under the surface to reach a novel collaborative relationship with communities. The findings demonstrate a need for sustained focus and commitment to understanding and making further social innovation visible, together with the fostering of capabilities to resource and incentivise wider implementation. The research offers a new perspective on social innovation, with a specific focus on communication to support local level community resilience building to flood risk.

Fatima Azhar, Ha Hong Bui, Valentijn R. N. Pauwels

ABSTRACT The vehicle stability criteria are based on experimental and theoretical studies that do not account for the unsteady nature of floods. The rapid variation of depths and velocities in floods causes an additional hydrodynamic force in the direction of the flow, destabilising a vehicle that would otherwise be safe in steady flow conditions. This study shows the changes in drag and lift forces when the vehicle encounters a floodfront or experiences accelerating flow past it. The numerical model built with smoothed particle hydrodynamics (SPH) is first validated for its use in studying unsteady flows by comparing it with 1:14 scale physical model results. The SPH model is then further extended to study the variation in drag and lift forces when the flow is accelerated past the vehicle from a steady state. The results show that the hydrodynamic drag can increase by 40%–50% in unsteady flows. This increase varies linearly with the acceleration of flow. Moreover, the build‐up of water in front of a watertight vehicle can further amplify the destabilising forces on the vehicle. It is the first such study wherein the hydrodynamic forces on a partially submerged object in high Reynolds number flow have been studied.

Leo van Rijn, Luitze Perk, Bas van Maren et al.

The particle size and the settling velocity of sediments are key parameters in sediment transport studies. However, it remains surprisingly difficult to determine particle size and settling velocity distribution of fine-grained sediments (mud-sand). A large range of methodologies exist to measure either the particle size distribution or to measure the settling velocity. An important influential parameter is the shape of fine-grained sediments, with clay minerals being shaped as plates rather than as spheres. Furthermore, the settling velocity of fine particles is influenced by turbulent shear and flocculation processes. Sometimes, the sediment samples are pre-treated (destroying inter-particle bonds) to measure the primary particle sizes involved while in other cases samples are not pre-treated in order to represent the effect of flocs. As a result, a large uncertainty exists in the way particle size and settling velocity should be measured. A range of methodologies (sedimentation, video camera, and laser-diffraction) to measure the settling velocity and particle size distribution in the field and in the laboratory is used and compared. The labour-intensive sedimentation methods measure a particle size distribution which can be used for sedimentation studies. The particle size distribution measured by the most commonly applied laser diffraction method is representative of the plate diameter of the clay particles, but the corresponding settling velocity is not correct. This difference can be explained by the shape of the clay particles through a derivation of the settling velocity of non-spherical particles resulting in a simple relationship to convert the particle size measured by laser diffraction to a representative particle size to be used in sedimentation studies. A comparison of the settling velocity measured by an in situ settling method and by a video camera method shows good agreement for high concentrations (> 2000 mg/L) but deviating results for low concentrations (< 500 mg/L).

Ann Crabbé, Sally Priest, Johan Munck af Rosenschöld et al.

Wei Huang, Shouqian Li, Yongjun Lu et al.

Rapid development of inland waterways and marine transportation has resulted in the construction of large ships and an increase in ship speed. Consequently, severe local scour erosion of restricted water beds occurs due to propellers, endangering the surrounding buildings and navigating in the scour area. Thus, investigating bed scouring caused by propeller jets for water-related structures and maintaining navigational safety in restricted waterways is highly important. Therefore, this work combines propeller jet wash flume experiments and dimensionless analysis to investigate the evolution of the three-dimensional (3D) morphology of bed scour with varying clearance heights and the use of noncohesive sediments. The temporal evolution of jet scouring was manifested mainly as the development of the scour area's length, depth, and width, and the entire scouring process could be divided into initial, development, and equilibrium stages. The initial stage occupied more than 60% of the scouring process, and the shape of the center profile of the scour area can be expressed by a third-order function. By analyzing the scour depth variation with time, this study proposed a logarithmic equation for the temporal development process of the maximum scour depth in the scour region, which was used to predict the variation in the maximum propeller depth on the surface of the noncohesive sand bed with time.

Badri Bhakta Shrestha, Mohamed Rasmy, Tomoki Ushiyama et al.

Abstract Understanding the impacts of climate change and conversion of paddy field areas in the future on agricultural production is an essential part of flood‐risk management. However, the quantitative impact of flood on agricultural crops in the far‐future under climate change, considering prospective changes in paddy area, is still not clearly understandable. This study thus focused on quantitative analysis of flood impact on rice crops under climate change using MRI‐AGCM climate model outputs for the past (1979–2002) and far‐future (2075–2098) periods for the Solo River basin in Indonesia. We developed a quantitative damage assessment method by coupling water and energy budget‐based rainfall‐runoff‐inundation model outputs and a depth‐duration‐damage flood loss model. We also analyzed land‐use and land cover changes to project future paddy areas. The future rice production in the study basin may decrease by 21% by 2048 and by 24.6% by 2076 compared with that in 2020, due to the conversion of paddy fields to other land cover classes. The average annual flood damage value of rice crops may increase in the future period (2075–2098) by 93.7% (average damage: 666.08 billion IDR) compared with that in the past period (1979–2002) (average damage: 343.7 billion IDR), due to climate change impacts alone.

Marisa Fuchs

ABSTRACT The floods in Western Europe in July 2021 demonstrated the diverse ways and varying paces at which neighborhoods recover from disasters. Based on two exemplary neighborhoods affected by the floods in the city of Hagen, Germany, this study examines the reconstruction process, highlighting the influence of social vulnerabilities and community resilience on private reconstruction processes. Despite differing contexts, both case studies demonstrated a significant reliance on external support during reconstruction. Individual needs varied based on social vulnerabilities within and between population groups, primarily manifesting as challenges in information dissemination and access to support services like funding and expertise. The findings reveal differences in the ability and capacity of neighborhoods to collectively address these vulnerabilities. While small neighborhood networks effectively facilitated information sharing in both cases, one case study relied more heavily on external assistance from nonprofit organizations for larger and longer‐term community‐driven initiatives. The study underscores the need for improvements in postdisaster reconstruction governance. Public authorities predominantly view neighborhoods as recipients rather than partners in the reconstruction process, without adequately addressing their social vulnerabilities within their governance approaches. Supporting local social infrastructures is crucial, as they connect formal reconstruction with the neighborhood, aiding resource access and resilience building.

Weiqi Ouyang, Zhiwei Li, Hanyou Lu et al.

The frequency and intensity of river floods in the Qinghai-Tibet Plateau (QTP) are increasing under the background of climate warming. In particular, the braided channel in the wide valley section in the Source Region of the Yangtze River (SRYR) has undergone drastic adjustments due to recent summer floods and further adjustments are expected in the future as climate change continues. Nonetheless, a lack of a quantitative description of the phenomenon persists. In order to unravel morphodynamic processes of a braided river under different flood flow discharges, a two-dimensional morphodynamic model was established using Delft3D to simulate the local braided channel in the Tuotuo River based on field observations and remote sensing images in the SRYR. The data of 1, 2, 5, and 10-yr flood hydrographs from 1985 to 2020 were obtained, using the hydrological data at the Tuotuohe Gauging Station. Specifically, two groups of actual flood hydrographs were used to simulate the hydrodynamic and riverbed adjustment of the braided channel reach. The following findings were revealed: (i) increases in discharge cause increases of the water level, and thus the flood flow erode and submerge the sandbars. During a flood, the previous branches are replaced by new branches and the braided channel shows a significantly different configuration after the flood. (ii) With the increase of the flood discharge, the amount of sediment erosion and deposition in the braided channels escalates. Specifically, the sediment erosion and deposition of the 10-yr flood will increase by 3.1 times and 4.7 times, respectively, in comparison with the 1-yr flood. (iii) When the discharge is greater than 180 m3/s, the braiding intensity in the wide valley section (>1.2 km) has a significant decreasing trend with the increase in the flood flow. When the discharge is less than 180 m3/s, the correlation between the braiding intensity and flood flow is not significant in the wide reach. (iv) The braiding intensity of the wide reach as flood frequency increases from the 1- to 2-yr events increases by 14.3%, 11.6%, respectively, and decreases for the 5- to 10-yr events by 3.2% and 10.8%, respectively. In the narrow reach, the increases are 25.5% and 11.2%, for the 1- and 2-yr events, respectively, and the decreases are 25.0% and 53.3% for the 5- and 10-yr events, respectively. The parabolic shape of the correlation between the braided intensity and flood discharge increases first, reaches a peak, and then decreases. Overall, the current study contributes to the understanding of the impact of gradually increasing flood discharge on the morphodynamics of braided rivers in the QTP.

Giulia Evangelista, Miriam Bertola, Günter Blöschl et al.

ABSTRACT Reservoirs play a crucial role in modifying natural flow regimes and mitigating flood peaks, yet their effectiveness depends heavily on operational strategies, particularly the initial storage level at the onset of a flood event. This study investigates, for the first time, the non‐linear effects of reduced initial storage on the relationship between flood peak attenuation efficiency and flood return period for about 250 large dams in Italy. We estimate flood hydrographs via a simplified hydrological model and apply full hydraulic routing under different scenarios of initial reservoir storage, informed by historical reservoir time series and regional flood seasonality. Our findings reveal that flood peak attenuation is highly sensitive to the initial storage level, with dam performance deteriorating sharply as flood return periods increase, especially when initial storage is high. Seven distinct classes of dams are identified based on their flood attenuation capacity relative to flood severity, highlighting non‐linear and threshold effects that are often overlooked in regional dam safety assessments. Notably, the commonly assumed full‐reservoir condition yields overly conservative estimates: under this assumption, approximately 20% of the dams reach their maximum allowed water level for return periods of 100 years or less. This national‐scale analysis provides new insights into regional differences in reservoir operation, particularly between hydropower‐oriented dams in the Alps and water supply reservoirs in southern Italy. By explicitly quantifying how reduced initial storage can enhance flood mitigation, the study offers practical recommendations for optimizing reservoir operations under current and future climatic conditions.

Karl-Erich Lindenschmidt

صفت اله رحمانی, محمد مظهری, جعفر طهماسبی

مقدمه استحصال و مهار نزولات آسمانی طغیان‌‌گر، به‌منظور جلوگیری از سیل و خسارت‌های ناشی از آن و همچنین، جلوگیری از فرسایش خاک، به‌‌عنوان منابع پایه تولید و محیط زیست، امری اجتناب ناپذیر است. در بیشتر کشورهای جهان، اعم از توسعه ‌‌یافته و در حال توسعه و همچنین توسعه‌‌نیافته، تحقیقات کاربردی و توسعه‌‌ای در بخش‌‌های مختلف اقتصادی و اجتماعی، از جمله بخش کشاورزی و منابع طبیعی، دارای حایز اهمیت بالایی است، به‌‌طوری‌‌که در هر مکان و در هر زمان، طرح و پروژه‌‌‌های اجرایی که بر مبنای نتایج حاصل از پژوهش بوده، موفقیت بیشتر و قابل اطمینان و پایدارتر بوده است. برای اجرای پروژه‌‌‌های اجرایی بر مبنای نتایج حاصل از تحقیقات انجام ‌‌شده، طی سالیان گذشته بر اساس اهداف از پیش تعیین شده، منابع مالی و امکانات نسبتا مناسبی در بخش کشاورزی و منابع طبیعی، از جمله بخش آبخیزداری، در نظر گرفته و هزینه ‌شده است. با این وجود، توجیه‌‌پذیر بودن آن از نظر اقتصادی و اجتماعی، همواره با بحث‌‌های فراوانی از سوی موافقان و مخالفان همراه بوده است. با این رویکرد، این پژوهش با هدف ارزیابی اثربخشی عملیات و پروژه‌‌‌های آبخیزداری ‌اجرا شده کاربردی شامل پخش سیلاب، سامانه سطوح آبگیر باران، سد زیرزمینی و تیمارهای مختلف حفاظت خاک، در حوزه آبخیز چنداب استان تهران، بر اساس نتایج حاصل از تحقیقات گذشته، انجام شده است. مواد و روش‌‌ها برای بررسی این موضوع، نتایج طرح‌ها و پروژه‌های شاخص تحقیقاتی و اجرایی آبخیزداری که مبتنی بر رفع مشکلات و مسایل حاکم بر حوضه‌ مورد مطالعه بوده است و با هدف کنترل رواناب و فرسایش خاک، بهبود وضعیت پوشش گیاهی و در نهایت، بهبود وضعیت اقتصادی و اجتماعی آبخیزنشینان در منطقه عملیاتی و اجرا شده است، شناسایی و اثربخشی آن‌ها در نیل به اهداف تعیین شده آبخیزداری، از نظر اقتصادی و اجتماعی مورد بررسی و تحلیل قرار گرفت. این پژوهش، از نوع پیمایشی و توصیفی بوده، داده‌‌های مورد نیاز پژوهش به‌صورت میدانی و با تکمیل پرسشنامه از ساکنین و ذی‌‌نفعان حوزه آبخیز مورد مطالعه و همچنین، با بررسی گزارشات مالی برای هزینه‌های انجام شده، جمع‌‌آوری شد. قبل از تکمیل پرسشنامه، سنجش اعتبار و روایی آن با استفاده از ضریب آلفای کرونباخ انجام شد. ضریب آلفای برآورد شده،‌‌ 0.87 بود که نشان‌‌دهنده یکپارچگی و هماهنگی در چارچوب پرسشنامه است. سپس، ارزش کنونی هزینه و درآمد در طی دوره زمانی مورد بررسی، برآورد ‌شد. روش منفعت‌‌-هزینه (B/C)‌‌، نرخ بازدهی و سود و همچنین سطح رضایت‌‌مندی و شاخص کارایی برآورد و اقتصادی تجزیه و تحلیل شده است. نتایج و بحث نتایج پژوهش نشان داد که کشاورزان و روستاییان ساکن در حوزه آبخیز مورد مطالعه، از اجرای پروژه‌‌های سد زیرزمینی و سامانه‌های پخش سیلاب بر آبخوان‌‌ ‌اجرا شده، رضایت کامل دارند و اجرای این پروژه‌‌ها در وضعیت حوزه آبخیز به لحاظ بهبود پوشش گیاهی، کنترل سیلاب، توسعه سطح زراعت، دامداری و بهبود درآمد و معیشت روستاییان اثرات مثبت قابل توجهی داشته است. پروژه‌های منتخب به اجرا در آمده، از نظر اقتصادی و اجتماعی اثربخش بوده است و دارای توجیه اقتصادی و اجتماعی هستند. به‌‌طوری‌‌که نسبت فایده به هزینه، 1.85 واحد و شاخص کارایی اقتصادی، 0.85 واحد برآورد شده است. نتیجه‌گیری نتایج حاصل از پژوهش نشان می‌‌دهد که پروژه‌های آبخیزداری اجرا شده در حوضه مورد مطالعه، از نظر اقتصادی و اجتماعی اثربخش است. از نظر اجتماعی نیز بیشتر بهره‌‌برداران ساکن در حوضه مورد مطالعه، از اجرای پروژه‌‌های آبخیزداری رضایت کامل دارند. با توجه به توجیه‌‌ پذیر بودن پروژه‌‌های آبخیزداری از نظر اقتصادی و اجتماعی، توصیه می‌‌شود، اجرای عملیات آبخیزداری در این حوضه و دیگر حوزه‌‌های آبخیز توسعه یابد. به‌منظور بهره‌‌مندی مردم محلی از دستاوردهای این طرح‌‌ها و همچنین، رضایت افراد محلی از پروژه‌‌های سابق، پیشنهاد می‌شود این طرح‌‌ها در محدوده اراضی بهره‌‌برداران انجام شود تا مشارکت حداکثری بهره‌‌برداران محقق شود و امکان واگذاری نگهداری از عملیات آبخیزداری انجام شده در حوزه‌‌‌های آبخیز با ساز و کار مشخص و تعریف شده، به مردم و بهره‌برداران محل فراهم شود.

روح انگیز اختری, محمد رستمی, بهرام ثقفیان et al.

مقدمه احداث بند اصلاحی در سرشاخه‌­ها، یکی از روش­‌های رایج مدیریت آبخیز برای کنترل رسوب، پایداری آبراهه و کاهش هیدروگراف سیل از بعد زمان تمرکز و دبی اوج محسوب می­‌شود. در ایران، با وجود قدمت ۵۰ ساله، در اجرای گسترده این سازه کوچک‌مقیاس به‌­وسیله ارگان‌های وابسته به سازمان منابع طبیعی و آبخیزداری کشور به ‌عنوان دستگاه اجرایی، همچنان روش ارزیابی کمی و کیفی مناسبی برای آن ارائه نشده است. در بیان اثربخشی این سازه، شبیه‌­سازی شرایط طبیعی در حالت وجود و عدم وجود این سازه در مدل‌­های هیدرولوژیکی و هیدرولیکی، اجتناب ناپذیر است. البته بازدیدهای میدانی و اندازه‌گیری پارامترهای مربوطه در عرصه نیز، در تدقیق شبیه‌سازی و هم بیان تقریبی اثربخشی، از اقدامات اولیه محسوب می­‌شود. بررسی‌های انجام شده نشان داد، در بسیاری از پژوهش‌­ها، اثر بندهای اصلاحی بر روی هیدروگراف رواناب مد نظر بوده است. شبیه­‌سازی بندها، به‌صورت هیدرولوژیکی با کمک تغییر در شیب آبراهه و زمان تمرکز حوضه و یا با استفاده از روش‌های روندیابی در مخزن انجام شده است که با توجه به فرضیات ساده شونده، برآوردی بیش از واقعیت ارائه می‌­دهد. شبیه­‌سازی هیدرولیکی دقیق­‌تر، اما پیچیدگی و موانع خاص خود را دارا است. لذا، در این پژوهش سعی بر آن شد تا علاوه بر بهره‌­مندی از دقت شبیه­‌سازی هیدرولیکی و نیز از عدم پیچیدگی روابط هیدرولوژیکی، اثربخشی وجود بندهای اصلاحی در هیدروگراف رواناب اعمال شود. اثربخشی بندهای اصلاحی با تعیین و اعمال ضرایبی در هیدروگراف خروجی آبراهه بدون بند اصلاحی، صورت گرفت تا هیدروگراف خروجی آبراهه با بند اصلاحی به‌دست آید.   مواد و روش­‌ها در این پژوهش، اثربخشی بندهای اصلاحی متوالی در کاهش هیدروگراف خروجی از یک کانال مثلثی با سه طول 1000، 2000 و 3000 متر در سه شیب طولی پنج، 10 و 15 درصد، با استفاده از مدل هیدرودینامیکیMIKE 11 ، مد نظر است. در این بررسی، فرض بر آن است که بندهای آبخیزداری متوالی با ارتفاع 2.5 متر از تاج بند پایاب تا پاشنه بند سراب در هر کانال مثلثی احداث شود. لذا، تعداد بندها بر اساس طول و شیب آن از 20 تا 180 عدد متغیر خواهد بود. در این پژوهش، هیدروگراف خروجی از کانال مثلثی به ‌عنوان متغیر وابسته و هیدروگراف ورودی به کانال، طول و شیب کانال، به‌ عنوان متغیرهای مستقل در نظر گرفته شد. تغییرات بیشینه جریان خروجی تحت دو سناریوی کانال بدون بند اصلاحی (سناریوی اول) و کانال با وجود بندهای اصلاحی متوالی پر از رسوب (سناریوی دوم) مورد بررسی قرار گرفت تا بتوان اثربخشی بندهای اصلاحی در یک آبراهه را با پارامترهای هیدرولوژیکی شبیه­‌سازی کرد. دو معیار سنجنده شامل درصد ضریب تسکین و درصد تغییر جریان برای بیان اثربخشی تعریف شد. درصد تغییرات دبی اوج هیدروگراف روندیابی شده در طول کانال نسبت به دبی اوج هیدروگراف ورودی یا به عبارتی اختلاف بین دبی ورودی و دبی خروجی برای سناریو و به ازای تغییرات طول مسیل، شیب و مقادیر مختلف هیدروگراف ورودی، "شدت روندیابی" نام‌گذاری شد. درصد تغییرات دبی اوج خروجی از سناریوی دوم نسبت به سناریوی اول هم تحت عنوان، درصد تغییر جریان، در نظر گرفته شد.   نتایج و بحث ارزیابی نتایج مدل برای روندیابی هیدروگراف در طول کانال به ازای تغییر متغیرهای مستقل در قالب دو سناریو، کاهش دبی اوج، افزایش زمان پایه هیدروگراف خروجی و زمان تاخیر ناشی از روندیابی را در پی داشت. وجود بندهای اصلاحی، تغییر پارامترهای فوق را دو چندان کرده است. هر چه شیب طولی آبراهه افزایش پیدا می‌­کند، میزان ذخیره در کانال کمتر شده و دبی خروجی و در نتیجه ضریب تسکین (کاهش دبی اوج خروجی نسبت به ورودی)، کاهش می­‌یابد. هر چه حجم جریان ورودی بیشتر باشد، ضریب تسکین کمتر خواهد بود. ضریب تسکین با شیب طولی، رابطه معکوس و با طول کانال، رابطه مستقیم دارد. در صورت اجرای بندهای اصلاحی، هر چه طول کانال بیشتر می‌­شود، به‌علت بیشتر شدن تعداد بندهای اصلاحی، میزان ذخیره در کانال افزایش یافته و کاهش شیب رخ خواهد داد و تغییرات دبی خروجی نسبت به دبی ورودی بیشتر خواهد بود، لذا، ضریب تسکین افزایش می­‌یاید. هدف اصلی این پژوهش، بیان ریاضی اثربخشی بندهای اصلاحی در کاهش دبی اوج هیدورگراف خروجی از مسیل بر اساس شرایط مختلف بود. پس از انجام اجراهای متعدد و بررسی انواع روش‌های مختلف، مشاهده شد که می‌توان اثرات بند اصلاحی بر روی یک آبراهه را به‌صورت اثر یک مخزن خطی به همراه یک تاخیر زمانی در انتهای کانال مدل کرد. به عبارتی، دو تابع مخزن خطی و تابع تاخیر زمانی بر روی متغیرهای وابسته اعمال می‌­شود تا متغیر مستقل به‌دست آید. برای هر زوج هیدورگراف (هیدروگراف خروجی از کانال بدون بند اصلاحی و دارای بند اصلاحی)، مقادیر، به‌ عنوان تابع مخزن خطی و  به‌عنوان تابع تاخیر زمانی برآورد شد. میانگین ضریب ذخیره (K) مخزن خطی برای طول­‌های 1000، 2000 و  3000 متر و برای سه شیب مورد بررسی به‌ترتیب 500، 1100 و 1400 ثانیه برآورد شد. میانگین زمان تاخیر نیز برای سه طول یادشده به‌ترتیب 540، 1750 و 3700 ثانیه، محاسبه شد. هر چه طول کانال بیشتر، شیب کانال کمتر، و دبی ورودی به کانال کمتر باشد، پارامترهای فوق بزرگتر شده و لذا، ضریب تسکین بزرگ‌تر می­‌شود. نتیجه‌گیری در صورتی‌که آبراه‌ه­ای برای احداث بندهای اصلاحی انتخاب شود و هیدروگراف خروجی از آن با استفاده از مدل­‌های تجربی، هیدرولیکی و هیدرولوژیکی در شرایط عدم وجود بندهای اصلاحی در دست باشد، هیدروگراف خروجی از آبراهه برای شرایط وجود سازه­‌های کوچک مقیاس، با اعمال ضرایب ذخیره مخزن خطی و زمان تاخیر به‌دست آمده از این پژوهش، شبیه­‌سازی و اصلاح خواهد شد. به این ترتیب، اثربخشی اجرای بندهای اصلاحی در کنترل سیل در آبراهه یادشده به‌دست خواهد آمد.

Olukemi Iyabode Lawanson, David Proverbs, Ridwan Lanre Ibrahim

Abstract The impacts of flooding on socioeconomic outcomes have become a global concern for governments, policymakers, and international organizations alike. The situation is particularly challenging in developing nations where poor communities are more vulnerable to the impacts of flooding. Consequently, this study investigated the impact of flooding on poor communities and poverty levels in Africa with particular reference to the Makoko community in Lagos State, South‐West Region of Nigeria. A survey design was employed with the collection of data through an environmental structured audio interview questionnaire (ESAIQ). Three Hundred and Fifty‐Eight participants located in the core six district areas of the community took part in the research. The impacts of flooding were found to be negative and a significant impediment to community development. Flooding was found to aggravate poverty levels and negatively impact educational status and community development. This study recommends more community‐based approaches to help raise awareness and support the co‐development of interventions that can help improve resilience.

Ashik Iqbal, M. Shahjahan Mondal, William Veerbeek et al.

Abstract Open‐source, satellite‐based digital elevation models (DEMs) are widely used for flood modeling. However, studies on effectiveness of these DEMs in depicting local‐level flood processes are limited. This study generated a high‐resolution digital terrain model (DTM) based on unmanned aerial vehicle (UAV) photogrammetry and used in a two‐dimensional (2D) hydrodynamic model (HEC‐RAS) to simulate the flood processes in a floodplain environment of the Jamuna River in northern Bangladesh. The effectiveness of a few satellite‐based DEMs was also compared with this DTM by using the DEMs in the same hydrodynamic model. Field data for two flood seasons were collected to develop the model. The results indicate that the 2D model with UAV‐based DTM provides the flood parameters, such as flood arrival time, depth, duration and extent, better than those from the satellite‐based DEMs. Of the open‐source DEMs, the FABDEM and the WorldDEM™ have the least errors and provide better results compared to the SRTM30, ALOS PALSAR, and ASTER DEMs. The UAV technique with ground control points and field measurements for the tree‐canopy and water areas is very useful in generating a fit‐for‐purpose DTM. The findings of this study would be useful for terrain generation and DEM selection for local‐level flood modeling elsewhere.

Rafael Silva Araújo, Miho Ohara, Mamoru Miyamoto et al.

Abstract Disasters worldwide tend to affect the poorest more severely and increase inequality. Brazil is one of the countries with high income‐inequality rates and has unplanned urbanization issues and an extensive disaster risk profile with little knowledge on how those disasters affect people's welfare. Thus, disasters often hit the poorest hardest, increasing the country's income inequality and poverty rates. This study proposes a method to assess the impact of floods on households spatially based on their income levels by conducting flood analysis and income analysis. The method is applied to the Itapocu River basin (IRB) located in Santa Catarina State, Brazil. The flood is assessed by conducting rainfall analysis and hydrological simulation and generating flood inundation maps. The income is evaluated using downloaded 2010 census data and a dasymetric approach. Flood and income information is combined to analyze flood‐impacted households by income level and flood return period. The results confirm the initial assumption that flood events in the IRB are more likely to affect the lowest‐income households rather than the highest‐income levels, thus, increasing the income inequality.

Lianhui Wu, Yoshimitsu Tajima, Hiroshi Sanuki et al.

Abstract Many urban flood models employ coarse grids to reduce the computational cost of real‐time forecasting. Such a coarse grid, however, may result in poor predictions of the discharge rate of surface water because of difficulties in representing the detailed features of drainage facilities. In the present study, an urban flood model that consists of a one‐dimensional (1D) river flow model, a two‐dimensional (2D) ground surface flow model, and a 1D sewer network model was developed. A coarse grid is used for the 2D ground surface flow model, and the tail networks of the sewer systems are neglected to reduce computational cost. A novel approach is proposed for determining the integrated water discharge from the ground surface to the trunk sewer network to retain the accuracy of a simplified coarse‐grid system. Numerical experiments were performed to evaluate the performance of the proposed method. Measured water levels at manholes were employed to examine the accuracy of the model. The results show that this approach significantly improves the accuracy of the simulated water level in a sewer network with enhanced computational efficiency.

Andreas Paul Zischg