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

Dibyendu Ghosh, Somen Das

Ziqiang Mao, Yiguo Ran, Qiao Chen et al.

Accurate quantification of sediment sources is essential for assessing bank erosion, mitigating reservoir sedimentation, and ensuring long-term sustainability. However, estimates for ungaged areas remain uncertain due to systematic monitoring gaps, and modeling efforts often lack reliability because of insufficient sediment records. To address this issue, grain size distributions (GSDs) were analyzed for two sediment cores, approximately 2.7 m in length, collected from the RangDu (RD) and ZhongXian (ZX) areas in the Three Gorges Reservoir (TGR), China. Suspended sediment from the mainstream and primary bank-derived materials from ungaged areas served as end members for quantitative source apportionment. Sedimentation periods were inferred by correlating temporal grain-size variations with precipitation intensity. The results indicate that both cores recorded continuous sedimentation from 2012 to 2022. The contribution of primary bank-derived materials from ungaged areas exhibited significant seasonal and spatial variations, averaging 36 % in the RD core (2012–2019) and 3.6 % in the slow-flow ZX core (2015–2022). Topographic and hydrodynamic conditions facilitated greater deposition of suspended materials in slow-flow areas compared to the main channel. The substantial contribution of bank-derived materials to reservoir sediment systems highlights the critical influence of wet-season rainfall on bank erosion and associated reservoir sediment. Nevertheless, given the current limitations in core sample quantity and temporal coverage, future studies should extend sedimentary conditions and temporal scope of sediment records for better understanding the impacts of precipitation, particularly extreme precipitation events, on bank erosion and reservoir sedimentation processes under global climate change.

Venera Hajdari Llapashtica, Laura Kusari, Lavdim Osmanaj et al.

Kabir Uddin, Sazzad Hossain, Birendra Bajracharya et al.

ABSTRACT In Bangladesh, where floods frequently occur, there is a severe annual risk to community displacement, agriculture, fisheries, livestock, public health, and food security. Extreme flooding events are becoming more common due to a combination of human‐induced climate change, irregular upstream river water flows, increased proportion of sediment distribution on the riverbed, institutional fragility, lack of planning regulations, and changing rainfall patterns. Effective flood management requires precise and timely flood mapping methodologies to adopt disaster risk reduction strategies and enable efficient response efforts. This study presents an approach that facilitates timely flood identification, improving emergency response, evacuation initiatives, relief distribution, and disaster risk reduction. This research introduces a novel methodology for expedited flood inundation mapping, using the August 2022, 2023, and especially the 2024 flood events in the Feni District as the primary case study. The study employs Google Earth Engine (GEE) and Sentinel‐1 synthetic aperture radar (SAR) data to accurately delineate flood inundation regions by utilizing vertical transmit and vertical receive (VV), vertical transmit and horizontal receive (VH), and VV/VH polarization bands. Water bodies characterized by lower backscatter values in VH polarization ranging from −41.15 to −24.06 dB and VV polarization from −31.66 to −15.94 dB were identified as suitable thresholds for flood inundation area delineation. To assess the accuracy of flood map, this study focuses on pixel‐based digital classification and machine learning (ML) techniques separately for flood inundation mapping. The classification accuracy values of 95.60% for the pixel‐based method and 94.40% for the random forest ML model specifically correspond to the 2024 flood event. This study developed a GEE‐based operational methodology by evaluating two innovative techniques designed for rapid flood inundation mapping to support effective flood management and disaster risk reduction efforts.

Desta Jula Bekalo, Amanuel Kumsa Bojer, Taye Girma Debelee et al.

ABSTRACT Floods are one of nature's most disturbing catastrophes, resulting in infrastructure damage, property devastation, and mortality. In Addis Ababa, flooding has significantly impacted residents and caused millions' worth of property damage in the last decade alone. It is continuously threatening and affecting city residents. This study focused on the spatial modeling of floods and the identification of areas susceptible to flood hazards in the city. Geographic information system (GIS) techniques combined with the information gain ratio (IGR) method were employed in this study. Five major flood hazard factors were identified: elevation, slope, rainfall, drainage density, and distance from drainage channels. The results show that 1.3% (7.1 km2) of the area is highly susceptible to floods, 29.4% (159 km2) is highly susceptible to heavy rains, 56% (302 km2) of the area is moderately susceptible, 12.5% (67.3 km2) of the area has low susceptibility, and less than 1% (4.2 km2) has very low susceptibility. Slope is the most influential factor (42.74%), followed by drainage density (28.21%), distance from drainage channels (18.8%), rainfall (7.69%), and elevation (2.56%). The sub‐cities of Nifas Silk Lafto and Akaki Kality are the most susceptible to flood hazards; areas with steep slopes trigger high runoff during heavy rainy periods and cause flood hazards on gentle slope surfaces. It is recommended that to improve the accuracy of identifying susceptible flood‐hazard locations, flooding simulation should be performed in conjunction with other variables and rainfall data (such as rainfall duration and intensity). Nevertheless, this research provides recommendations to municipal administration decision‐makers regarding strategic management in the prioritization of flood‐hazard zones.

Gabriel Morin, Mathieu Boudreault, Jason Thistlethwaite et al.

ABSTRACT Flood risk management (FRM) involves planning proactively for flooding in high‐risk areas to reduce its impacts on people and property. A key challenge for governments pursuing FRM is to pinpoint assets that are highly economically exposed and vulnerable to flood hazards in order to prioritize them in policy and planning. This paper presents a novel flood risk assessment, making use of a dataset that identifies the location, dwelling type, property characteristics, and potential economic losses of Canadian residential properties. The findings reveal that the average annual costs are $1.4B, but most of the risks are concentrated in high‐risk areas. Data gaps are uncovered that justify replication through local validation studies. The results provide a novel evidence base for specific reforms in Canada's approach to FRM, with a focus on insurance that improves both implementation and effectiveness.

Imogen Hobbs, Valentin Lucet, Jennifer M. Holzer et al.

ABSTRACT Effective social‐ecological fit is considered essential for properly managing social‐ecological systems. Despite this importance, the concept of social‐ecological fit lacks the following: clarity in scope and definition, a practical quantitative method to assess effectiveness, and methods capable of equally assessing the social and ecological factors within the system being managed. To address these knowledge gaps, we reviewed how social‐ecological fit has been conceptualised in the literature and then tested the use of Bayesian Belief networks and analysis to quantitatively assess “fit” using the case of flooding in the North Onslow saltmarsh region of Truro, Nova Scotia. The objective of this study was to assess which decision‐making choices would most likely reduce flood risk, and therefore achieve the best ‘fit’. Drawing from a combination of existing literature and local expert opinion, we identified the relevant factors influencing flood risk in the region, their relationship to each other and their combined relationship to local flood risk. Ice jam frequency, high tide frequency and dyke maintenance were found to have the most influence. The results of this study can be used to inform local flood‐risk‐related decision‐making in Truro and act as a model for quantitatively assessing social‐ecological fit in other risk management settings.

Zihao Tang, Bruce W. Melville, Naresh Singhal et al.

Microbially induced calcite precipitation (MICP) is an emerging method for mitigating scour and erosion. The present study experimentally investigates the efficacy of MICP as a local scour countermeasure for offshore wind turbine monopile foundations under both clear water and live-bed conditions. Bacteria were enriched using activated sludge. Analyses conducted included urease activity monitoring, unconfined compression testing, and examination using scanning electron microscopy. Various depths for the MICP protection elevation were tested in clear water conditions, and the resulting scour topography was mapped using photogrammetry techniques. Investigations were conducted on bedform migration and leading-edge scour upstream of the MICP protection, considering various protection elevations. The results indicated that MICP protection can provide effective scour protection under both clear water and live-bed conditions. Discussions in this study also extend to the erosion and potential collapse of the MICP protection structure. Flow undercut rate were also examined for evaluating potential failure of MICP protection structures, and the elevation of MICP protection has a significant influence on mitigating flow undercutting. Full protection efficiency was observed under clear water conditions when the MICP protection elevation was at the bed level and the flow intensity was relatively low (V/Vc = 0.65), while the highest average protection efficiency (47.73%) among all flow intensities was recorded when the MICP protection elevation was at 0.6D below the bed.

Serigne Bassirou Diop, Yves Tramblay, Ansoumana Bodian et al.

ABSTRACT Devastating flood events are recurrently impacting West Africa. To mitigate flood impacts and reduce the vulnerability of populations, a better knowledge on the frequency of these events is crucial. The lack of reliable hydrometric datasets has hitherto been a major limitation in flood frequency analysis at the scale of West Africa. Utilising a recently developed African database, we perform a flood frequency analysis on the annual maximum flow (AMF) time series, covering 246 river basins in West Africa, between 1975 and 2018. Generalized extreme value (GEV) and Gumbel probability distributions were compared to fit AMF time series with the L‐moments, Maximum Likelihood (MLE) and Generalized Maximum Likelihood (GMLE) methods. Results indicated that the GEV distribution with the GMLE method provided the best results. Regional envelope curves covering the entire West African region with unprecedented data coverage have been generated for the first‐time providing insights for the estimation in flood quantiles for ungauged basins. The correlation between flood quantiles and watershed properties shows significant correlations with catchment area, groundwater storage, altitude and topographic wetness index. The findings from this study are useful for a better flood risk assessment and the design of hydraulic infrastructures in this region, and are a first step prior to the development of regional approaches to transfer the information from gauged sites to ungauged catchments.

Karl-Erich Lindenschmidt

Gerben J. Koers, Steven A. Forrest, Jitske vanPopering‐Verkerk

Abstract Climatic changes can cause unpredictability in flood regimes that traditional flood risk management (FRM) approaches may struggle with. Therefore, flood resilience is seen as a supplementation to these approaches, putting a larger emphasis on flood acceptance and minimising consequences. An (emergent) group contributing towards flood resilience is civil society. This paper examines how civil society contributions can be furthered and guided in the Netherlands as well as exploring potential limitations in doing so. To achieve this, England is used as a good practice example due to a more developed and defined role for civil society being present here. Data were collected on both actual (England and the Netherlands) and potential (The Netherlands) civil society contributions. These were compared to identify potential avenues for Dutch civil society contributions to flood resilience that can be further investigated. The research shows that the most promising avenues are improving advocacy from citizens, improving local flood awareness and developing relationships between FRM authorities and existing citizen groups that can be harnessed and mobilised to support flood resilience. Additionally, the research also provides insights into potential limitations for transferring resilience approaches from one context to another beyond the cases discussed in this publication.

Kai Gao, Zhiyong Yang, Xichao Gao et al.

Abstract 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.

Aakanchya Budhathoki, Tomohiro Tanaka, Yasuto Tachikawa

Abstract Rice is a major agricultural crop in Thailand, while paddy fields near river lines are exposed to high flood risk. This study assesses rice exposure and economic flood risk under future climate in the Lower Chao Phraya River Basin, Thailand. To encompass various flood events, this study estimates the frequency of rice economic damage by employing a large ensemble climate projection dataset based on database for Policy Decision making for Future climate change (d4PDF). Results show that, in the 4‐K warmer climate, the 100‐year exposed cultivation area and duration will increase approximately by 1.2–1.4 and 1.1–1.2 times, respectively. Decreased rice production is evaluated as monetary damage through several fragility curves. The economic damage by the 2011 flooding is estimated as 11.25 billion Thai Baht, while the estimation varies from the fragility curves employed. In the 4 K warmer climate, regardless of the fragility curves, 100‐year rice damage is projected to increase by 1.2–1.4 times. The 2011 flooding is larger than all 3000‐year simulations in the past climate, whereas extreme events in the 4 K warmer climate showed higher damage than the 2011 flooding, indicating that agricultural damage corresponding to the 2011 flooding may occur more frequently in the future climate.

محسن آرمین, حمیده زاهدی خواه, ملیحه مزین

مقدمه بندهای اصلاحی، سازه‌‌های ساده و نسبتاً کم هزینه هستند که به‌دلیل عدم نیاز به مصالح و تکنولوژی خاص، به‌طور گسترده‌‌ای جهت کنترل رسوب در حوزه‌‌های آبخیز مورد استفاده قرار می‌‌گیرند. این نوع بندها بیش‌‌ترین حجم عملیات اصلاحی آبخیزداری را در ایران به خود اختصاص می‌‌دهند. لذا، با توجه به فراوانی احداث و در نتیجه هزینه ساخت، بررسی عملکرد آنها در حوزه‌‌های آبخیز جهت شناسایی نقاط قوت و ضعف آنها ضروری است. ارزیابی تله‌‌اندازی رسوب بندهای اصلاحی و انتخاب درست شاخص‌های اثرگذار بر عملکرد رسوب‌‌گیری آنها هدف اصلی این پژوهش است.   مواد و روش‌‌ها در این پژوهش، ارزیابی بندهای اصلاحی از منظر عملکرد رسوب‌‌گیری در حوزه آبخیز نهضت آباد در شهرستان کهگیلویه مورد بررسی قرار گرفته است. بدین منظور بعد از تعیین شاخص‌های مرتبط با حجم رسوبات نهشته شده در پشت 11 بند اصلاحی منتخب و محاسبه حجم آنها، میزان رسوب‌‌گیری ابتدا اندازه‌‌گیری و سپس با محاسبه سه ضریب تله‌‌اندازی رسوب متفاوت برآورده شده است. درنهایت، هم با محاسبه نسبت تحویل رسوب، تولید رسوب اندازه‌‌گیری شده و برآورده شده به تلفات خاک معادل آن در سطح زیرحوضه‌‌های بالادست بندهای اصلاحی تبدیل شد.     نتایج و بحث نتایج نشان داد که میزان تولید رسوب ویژه اندازه‌‌گیری شده در زیرحوضه‌‌های بالادست بندهای اصلاحی از 0.001 تا 1.80 و به طور میانگین 0.13 تن در هکتار در سال است. با در نظر گرفتن نسبت تحویل رسوب که از 18 تا 51 درصد برای بندهای اصلاحی منتخب متغیر بوده، این میزان تولید رسوب معادل 0.01 تا 2.1 و به‌طور میانگین 0.3 تن در هکتار در سال تلفات خاک در سطح زیرحوضه‌‌های بالادست بندهای اصلاحی است که در مقایسه با اعداد و ارقام ارائه شده برای متوسط تلفات خاک در اغلب حوزه‌‌های آبخیز ایران عدد بسیار کمی است. با در نظر گرفتن ضرایب مختلف تله‌‌اندازی رسوب، مقادیر میانگین برآورد شده تولید رسوب ویژه برای زیرحوضه‌‌های بالادست بندهای اصلاحی 2.88، 7.46 و 0.87 تن در هکتار در سال متغیر است که این میزان رسوبات به‌ترتیب معادل 9.41، 30.5، 3.49 تن در هکتار در سال تلفات خاک است که در مقایسه با میزان متوسط تلفات خاک حوزه‌‌های آبخیز ایران، اعداد معقول‌‌تر و منطقی‌‌تری به‌نظر می‌‌آیند.   نتیجه‌‌گیری با توجه به عوامل مؤثر بر ضریب تله‌‌انداری رسوب، می‌‌توان گفت که اگر بندهای اصلاحی در نقطه‌‌ای از آبراهه احداث شوند که نسبت ظرفیت ذخیره مخزن بند به مساحت زیرحوزه آبخیز بالادست بندها بیشتر باشد، ضریب تله‌‌اندازی رسوب در بندها افزایش یافته که به لحاظ کارایی رسوب‌‌گیری مطلوب‌‌تر است. با بررسی مقدار ضرایب تله‌‌اندازی رسوب در بندهای اصلاحی مورد بررسی در حوزه آبخیز نهضت آباد که نسبتاً کم هستند، می‌‌توان گفت که یکی از دلایل کم بودن ضرایب، کاهش نسبت ظرفیت ذخیره مخزن بند به مساحت حوزه آبخیز بالادست آنها است. لذا، چنانچه اصول علمی در انتخاب صحیح پارامترهای مؤثر بر رسوب‌‌گیری بندهای اصلاحی رعایت نشود، اجرای چنین پروژه‌‌هایی اثربخشی لازم و کافی را ندارد، ضمن اینکه رسوب اندازه‌‌گیری شده در این بندها و تلفات خاک معادل آن مبنایی برای اجرای سایر اقدامات آبخیزداری در حوزه‌‌های آبخیز است و چنانچه دقیق نباشد، می‌‌تواند منجر به عدم اثر بخشی این اقدامات و محاسبات نادرست شود.

Antonis Skouloudis, Walter Leal Filho, Panagiotis Vouros et al.

Abstract Floods signify one of the most common, widespread and destructive natural perils, affecting approximately 250 million people and causing billions in losses on an annual basis. Such high impact – low probability environmental perturbations can cause abrupt changes and disruption to business entities in flood‐prone areas in terms of asset damages, operational interruptions and increased costs which result in loss of capital and labour, declining revenue and growth. It is therefore critical for businesses to identify such risks and, ultimately, to effectively build their resilience to such physical challenges. Small and medium‐sized enterprises (SMEs) in particular are more ill‐prepared to face flooding compared to large companies. Understanding the ability of SMEs to become more resilient to floods is crucial as they account for 99% of all enterprises, constitute the major employer and contributor of the total value‐added of the private sector. In this study, a composite index of factors linked to the resilience capacity of SMEs to flooding is proposed and tested. A sample of Greek SMEs located in three flood‐prone areas (n = 391) was administered a structured questionnaire pertaining to cognitive, managerial and contextual factors that affect the ability to prepare, withstand and recover from flooding events. Through the proposed index, a bottom‐up, self‐assessment, approach is set forth that could assist in standardising such assessments with an overarching aim of reducing the vulnerability of SMEs to floods. This is achieved by examining critical internal and external parameters affecting SMEs' resilience capacity which is particularly important taking into account the limited resources these enterprises tend to have at their disposal and that they can generate single points of failure in dense supply chain networks.

حمزه سعیدیان, حمیدرضا مرادی

با تعیین آستانه شروع رواناب و فرسایش به‌وسیله شبیه‌­ساز باران می­توان با سرعت و دقت بیشتر و هزینه کمتر مقدار بارانی را که سبب وقوع رواناب در شرایط مختلف می­‌شود، مشخص کرد. پس از تعیین آستانه شروع رواناب و فرسایش در هر منطقه با استفاده از روش­‌های بیولوژیک و عملیات مختلف می­‌توان از تبدیل رواناب به سیلاب جلوگیری کرد. در این تحقیق، با توجه با این‌که شروع آستانه رواناب و فرسایش هم‌زمان اتفاق می­‌افتد و به اشتباه فقط اصطلاح شروع آستانه رواناب را در تحقیقات مختلف به‌کار می‌­برند و کمتر به اصطلاح شروع آستانه فرسایش پرداخته می­‌شود، به‌منظور تعیین مهم‌ترین عوامل موثر در شروع آستانه هم‌زمان رواناب و فرسایش کاربری­‌های مختلف نهشته­‌های سازند­های آغاجاری و گچساران، بخشی از حوزه آبخیز مرغا و کوه گچ شهرستان ایذه با مساحت 1609 و 1202 هکتار انتخاب شد. این تحقیق به‌منظور تعیین رابطه بین آستانه شروع رواناب و فرسایش به­‌وسیله شبیه‌ساز باران با برخی خصوصیات فیزیکی و شیمیایی خاک مانند درصد ماسه خیلی ریز، شن، رس، سیلت، اسیدیته، هدایت الکتریکی، رطوبت، کربنات کلسیم و ماده آلی در کاربری‌های مختلف سازند­های آغاجاری و گچساران انجام شد. سپس، نمونه‌برداری زمان آستانه شروع رواناب و فرسایش در 13 نقطه و با سه بار تکرار در سازندهای آغاجاری و گچساران در شدت­‌های مختلف بارش 0.75، 1 و 1.25 میلی‌متر در دقیقه در سه کاربری مرتع، منطقه مسکونی و اراضی کشاورزی به کمک دستگاه شبیه‌ساز باران انجام شد. به‌منظور انجام تحلیل­‌های آماری از نرم‌افزار SPSS و EXCEL استفاده شد. مهم‌ترین عوامل موثر در آستانه شروع رواناب و فرسایش به کمک رگرسیون چند متغیره شناسایی شدند. به­‌طور کلی، در سازند گچساران در هر سه کاربری بیشترین نقش را در افزایش زمان شروع رواناب و فرسایش، رس و کربنات کلسیم از خود نشان دادند و بیشترین نقش را در کاهش زمان شروع رواناب و فرسایش در سازند گچساران، ماسه خیلی ریز و رطوبت از خود نشان دادند. ولی در سازند آغاجاری در هر سه کاربری بیشترین نقش را در افزایش زمان شروع رواناب و فرسایش، رس و ماده آلی از خود نشان دادند و بیشترین نقش را در کاهش زمان شروع رواناب و فرسایش در سازند آغاجاری، ماسه خیلی ریز و شن و شوری خاک از خود نشان دادند.

Patrick Ken Kalonde, Blessings Chiepa, Alick Chisale Austin et al.

Ali Mohajervatan, Nahid Tavakoli, Hamidreza Khankeh et al.

Abstract One of the most essential purposes of the health system is to ensure that people affected by various disastrous events, such as floods, have access timely to basic health services. Therefore, enhancing the preparedness and response plans for such events should be a national priority. Because of the complexity and devastating impacts of floods on public health, it is a crucial to understand the various aspects of flood experience in the country. The experiences of managers and operational staff from various units of the Iranian health system are a valuable source for understanding flood complexities. These experiences were explored using 19 semi‐structured interviews with people who had firsthand experience of this phenomenon. Based on the results, in order to provide a flood response plan, it is necessary to adhere to the principles and foundations that can meet the needs arising from the flood. Our study showed that the health system's response to flooding can be divided into two categories: initial and specific functions. A comprehensive response requires an initial function to prevent flood impacts, and specific functions are needed to prevent and treat flood‐related diseases. These results could form the basis for the health system's response to future floods.

Mojgansadat Azimi, Abolfazl Sharifian, Vahideh Riazinia et al.

Abstract Flood disaster is considered a significant natural hazard due to their devastating effects. The 2019 flood in Northern Iran drastically affected the lives of Indigenous Turkmen pastoralists. This work assesses the vulnerability of the pastoral families living in flood regions. We used the Geographical Information System, Multi‐Criteria Decision Analysis, and semi‐structured interviews to analyze the flood vulnerable areas. Initially, we interviewed 20 individuals and then formulated a questionnaire completed by 69 pastoralists in rangelands affected by floods in Golestan province. Result showed that 91% of the participants thought road networks and 76% thought livestock were the most affected components of the rangeland ecosystems in the 2019 flood. Moreover, we found supplementary feeding, watering costs, and forage quantity to be the most affected items in the economy of pastoral families. The main rangeland degrading factors were overgrazing, climate change, drought, and water shortages. The main reasons for overgrazing were the high prices of supplementary feeding, low forage productivity of the rangelands, and financial difficulties of pastoralists. We indicated that pastoral communities in the semi‐arid rangeland of Northern Golestan were highly vulnerable to flood. Hence, proper management of rangelands and building pastoral family resilience requires the attention of nature conservationists and management organizations at the national level.

Jingchun Fan, Brett D. Hambly, Yanqing Sun et al.