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

Eleanor Starkey, Mark Davinson, Sophie Liu et al.

ABSTRACT Nature‐based solutions are increasingly recognised for their potential to address multiple sustainable development goals and transform degraded urban areas into liveable spaces. Sustainable drainage systems (SuDS), increasingly considered a sub‐set of these, are widely used to improve urban flood and climate resilience. Although they can enhance water quality, water quantity, biodiversity and amenity when implemented effectively, they often underperform, underdeliver and are designed with a single goal in mind. These complex demands require new ways of working to integrate diverse perspectives into a single scheme or space, such as placemaking, which shapes spaces with local people to enhance connection, meaning and long‐term care. This paper argues for leveraging nature‐based water management to maximise urban resilience and proposes a community‐led framework to ensure that sustainable, multi‐benefit solutions are designed with and for local citizens. We introduce the UK's Defra‐funded ‘SuDS+’ project, which pilots SuDS through a community lens. Based on visioning, prioritisation, co‐design, implementation and legacy, a framework is being tested in County Durham (UK) to ensure community involvement at every stage. This approach expands beyond traditional flood risk management in several ways. We present empirical examples from the community ‘visioning’ and ‘prioritisation’ stages that initiate this placemaking process, then demonstrate how suggestions can be shortlisted using an innovative filtering tool to transform ideas into coherent ‘SuDS+ concepts’. These steps balance flood risk (SuDS) with community (‘+’) needs ahead of the co‐design and implementation phases. We then share a series of reflections and refinements. Our research demonstrates that community members offer a broader range of ideas and are more likely to engage with, understand, support and care for solutions that they co‐design within their neighbourhood. Significant in‐person engagement is crucial as urban flooding is not a top priority for them; jobs, housing, education, accessible spaces and a sense of pride and ownership are. Leveraging these priorities to design multifunctional solutions for (and by) flood risk management could catalyse sustainable urban development and reveal the true potential of nature‐based flood management. Such an approach could transform the water sector by fostering cross‐sector collaborations to generate cost‐effective, high‐quality spatial and socially meaningful solutions. Moving forward, participatory governance, effective partnerships, diverse skills, robust monitoring frameworks and realistic policy updates are required to streamline SuDS delivery, avoid duplication and demonstrate multi‐benefit impacts.

Pritam Kumar, Anurag Sharma

The study aimed to explore three-dimensional turbulent flow properties and bed morphology in a partially vegetated channel with sand bed conditions. Presence of flexible vegetation in the river and its interaction with the flow are of great significance in understanding the momentum and mass transport in the flow. Experiments were conducted in a straight, tilting rectangular flume with staggered emergent vegetation covering half of the channel width. The results show that the presence of vegetation diverts streamwise velocity from the vegetated side to the non-vegetated side. The study reveals that the presence of vegetation leads to an increase in turbulent intensity, turbulent kinetic energy, and Reynolds shear stress at the transition area between the vegetated and non-vegetated sides of the channel. This increase is attributed to higher transverse flow and momentum exchange in the transition area between the vegetated and non-vegetated sides. In the vegetated side, the vegetation serves as an obstruction, reducing turbulent intensity, turbulent kinetic energy, and Reynolds shear stress compared to the transition area between the vegetated and non-vegetated sides. This reduction in turbulence supports the stability of bed materials and promotes sediment deposition. The presence of vegetation significantly alters the secondary current in the channel. Scour depth along the non-vegetated side was higher than the vegetated side, mainly because the flow concentrated in the centre and non-vegetated side of the channel. The investigation determines that the existence of vegetation on the vegetated side effectively protects against bed erosion and sediment transport. Understanding the impact of emergent flexible vegetation on flow properties and sediment transport can inform decisions about vegetation layouts in river ecosystems.

Fafali R. Ziga‐Abortta

ABSTRACT Flood disasters with cascading characteristics traverse decision‐making levels involving a spectrum of actors. Actors involved in Flood Disaster Risk Management (FDRM) form networks to implement related policies. Utilizing an ideational policy network approach, this study contributes knowledge to the role of material and ideational exchanges in policy networks. Two empirical case‐study research questions are posed: (1) How is Ghana's FDRM policy network structured in relation to information and resource exchange and trust? (2) How does ideational (mis)alignment influence this network? Methodologically, a quantitative Social Network Analysis is combined with qualitative interpretations. Results show that the current policy network primarily facilitates “information and knowledge exchanges” dominated by centralized state agencies reemphasizing traditional conceptualizations of the state as the primary duty bearer of disaster management. The network benefits from influential actors who act as brokers, fostering shared ideas of resolute problem‐solving despite challenges, while maintaining strategic diplomatic ties that enable network endurance. The study reveals complex patterns of ideational alignment and misalignment, where actors' problem definitions do not necessarily correspond with their preferred solutions. Four distinct scenarios emerge: full alignment, partial alignment, partial misalignment, and complete misalignment of shared ideas, demonstrating how material and ideational dimensions interact to shape policy implementation outcomes.

Wendy Sharples, Jiawei Hou, Katayoon Bahramian et al.

ABSTRACT The Hawkesbury‐Nepean valley has a long history of hazardous flooding dating back to when records began, in the 18th century. It is one of the largest coastal basins in the eastern Australian region and supports a large population, agriculture, and industry, as well as being an important environmental asset. Multiple flooding events with differing socioeconomic impacts occurred in the valley between 2020 and 2022, brought about by a rare triple La Niña event—only the third since 1900. In this study, upon examination of the four significant floods in the area, the reasons for the variation in impacts are explored by investigating the climate drivers and antecedent conditions preceding these events, the streamflow during the events, and the hazard footprints themselves. It was found that antecedent landscape conditions exerted a first‐order effect on the hazard footprint's size and thus impact. These results imply that with the current landscape drying trends and projected increase in landscape dryness for this region, the projected increase in extreme rainfall events will not affect the flood hazard footprint of medium‐sized floods. Thus, impacts from flooding will not necessarily increase in severity in this region in the future.

Hui Liang, Ruijing Jiang, Ronghua Liu et al.

Rainfall-induced flash floods often trigger active sediment transport and substantial morphological changes, which in turn affect flood dynamics. Previous numerical studies have mostly overlooked the strong interactions between flow, sediment transport, and morphological evolution, and inevitably their impacts on flash flooding have remained poorly understood. Here a two-dimensional (2D) coupled shallow water hydro-sediment-morphodynamic (SHSM) model is applied to reconstruct an extreme flash flood in the Jiuyuan Gully catchment, Beijing, China, in July 2023. The impacts of sediment transport and morphological change on the flash flood are evaluated by comparing the results of a shallow water hydrodynamic (HD) model and the SHSM model. The SHSM model is shown to outperform the HD model in reproducing the observed maximum water levels, as sediment transport and morphological changes are explicitly taken into account. Bed load sediment prevails, while its transport rate may amount up to 30 kg/(m·s) in the flood conveyance channel and deviate from the transport capacity determined in line with local flows, as sediment entrainment is hindered by the concrete-lined bed. Aggradation in the flood conveyance channel is significant, reaching 3.0 m locally. Accordingly, the water level increases, leading to overbank flooding and extended inundation over the floodplains and adjacent areas. Consequently, flash flooding is exacerbated. The current findings highlight the critical role of morphological change induced by active sediment transport in modifying flash flooding, underscoring the significance of morphological change for practical flood warning and development of effective risk management strategies.

Selina Schaum, Stefanie Stenger‐Wolf, Holger Schüttrumpf et al.

ABSTRACT Temporary structures are important for a rapid recovery phase after extraordinary flood disasters we cannot protect ourselves from. Long‐term temporary structures are particularly relevant when infrastructures are destroyed that require a longer reconstruction phase. In addition, they offer the opportunity of more time to build resilient critical infrastructure (CI). The term “long‐term temporary” is used in the study to emphasize that these temporary solutions are not only used for a short period of time (less than 6 months). On the example of the recovery in the Ahr valley after the 2021 flood, the authors diagnosed the importance of practice examples on long‐term temporaries when ad‐hoc solutions are needed, as well as the long persistence of some of the temporary solutions. A systematic literature analysis was conducted, as limited research in long‐term temporaries exists. We evaluated how many scientific papers on the topic of long‐term temporaries for CI after flood disasters can be identified after a parameter‐oriented literature analysis and which aspects are dealt with. The literature analysis is based on seven search parameter combinations and covers the areas of drinking water supply, power supply, sewage disposal, telecommunications, bridges (transport systems) and gas supply. 138 publications were identified as relevant, with 43 broaching the issue of temporary solutions after flooding. The most common keyword is “critical infrastructure” (CI) with only 3.7%, followed by “flood” with only 3.4%. Most studies on temporary solutions evaluate temporary bridges, followed by drinking water supply. Military engineering plays a key role in providing temporary bridges, which explains the good supply and documentation. The authors analysed temporary structural solutions (long‐term temporaries) based on on‐site observations and the close collaboration with municipalities within the KAHR‐project during the recovery phase of the region. The case study presents some specific long‐term temporary solutions for bridge constructions and flying pipes to temporary drinking water treatment systems and sewage treatment plants. Another key finding is that long‐term temporary structures are very diverse and have varying life spans (shorter for telecommunication and drinking water supply and longer for bridges and sewage disposal) as well as different requirements in technicality and durability (e.g., lower challenges in drinking water supply, higher requirements for bridges). It is therefore important to explore this area in terms of risks and design options, which has a direct impact on flood risk management, as it could make the use of long‐term temporary structures more routine during the emergency management phase.

Anwarelsadat Eltayeb Elmahal, Wifag Hassan Mahmoud, Ahmed Abdalla et al.

ABSTRACT Climate change and Land Use Land Cover Change (LULCC) impact on rainfall and runoff is globally evident. However, flash flood impacts on drylands are rarely investigated. A comparable watershed in the dryland of Sudan experienced devastating flash flood impacts for the last four decades (1980s–2020s). The unexpected severity of the 2013 flash flood prompted an investigation into hydrologic and LULCC to determine its cause. We combined spatial cloud computing with hydrological analysis to investigate the relationship between LULCC and peri‐hydrological processes for four decades. The Landsat time series analysis shows significant LULC changes: agricultural and rangelands decreased by over 80%, while urban and barren areas increased by 81% and 31%, respectively. The daily rainfall analysis shows that rainstorms exceeding 40 mm were classified as destructive only under wet antecedent soil moisture conditions (1988, 2009, and 2019). Unexpectedly, the 41 mm rainstorm in 2013 occurred under dry conditions. The respective flood magnitude was 4.6 Mm3 according to the US‐Natural Resources Conservation Service (US‐NRCS). This represents only 14% of the potential runoff under wet conditions (32.3 Mm3) for the same rainstorm. Therefore, the devastating impact of the rainstorm emphasizes the impact of LULCC on flood dynamics in peri‐urban areas of drylands.

Alistair Geddes, Andrew R. Black, Michael Cranston

Abstract Direct messaging involving simultaneous mass transmission of brief text or voice messages to large numbers of recipients has become a frontline method in flood hazard communications. Messages are intended to serve as cues, drawing recipients' attention to changing conditions, yet the actual effectiveness of direct messaging among recipient groups remains under‐examined. This article considers direct messaging within the Floodline public flood warning service in Scotland, implemented by the Scottish Environment Protection Agency (SEPA). Within Floodline, messaging is integrated with alerting and warning information, termed straightforwardly ‘Flood Alerts’ and ‘Flood Warnings’. Collaborating with SEPA, we conducted an online questionnaire survey of registered Floodline direct messaging recipients. In this article, our analysis focusses specifically on responses to three open‐ended questions included in this survey, with an iterative qualitative coding approach employed to interpret themes of meaning from the question responses. This analysis gives a clear indication that recipients value Floodline and direct messaging. However, there are also questions raised over the utility of Flood Alerts and related messaging, which we elaborate in the findings and discussion, along with the scope for adding content, linking to other information, and developing closer relationships. Changes being developed by SEPA align with several of these findings.

Alex Hall

Appalachian History Series Setting the Scene On the South Fork Holston River just southeast of Bristol, Tennessee, the Tennessee Valley Authority built South Holston Dam to curb destructive flooding and to supply hydropower in the mid-twentieth century. The project impounded a long, slender reservoir that reaches about 24 miles into Virginia, and it became the upstream anchor of TVA's Holston River system.

Lijun Dong, Xiaohua Dong, Yaoming Ma et al.

Abstract The frequency analysis method is commonly used to calculate design floods. Under the double challenge of the non‐stationary situation under the changing environment and the inadequate length of flood series, developing a new method to integrate the historical extraordinary floods into the non‐stationary frequency analysis is essential. First, the Multi‐Model Ensemble projections of temperature and precipitation based on Global Climate Model outputs were employed to drive the Soil & Water Assessment Tool hydrological model for runoff simulation. Then, the Integrated Time‐Varying Moment (ITVM) model was developed to re‐analyze the design floods based on the Pearson‐III distribution. The calibrated SWAT model can satisfactorily simulate the rainfall‐runoff relationship in the Yalong River basin. The developed ITVM model is effective to conduct the design flood frequency analysis to cope with the problems of insufficient length and non‐stationarity of the flood series. The design flood values of Maidilong station show an obvious increase, with variations of 6.5%–9.4%, 2.9%–12.3%, and 16%–33.7% for SSP1‐2.6, SSP2‐4.5, and SSP5‐8.5, respectively. The significant increase of low frequencies (p = 0.2%, p = 0.1%) floods, especially for SSP5‐8.5 scenario, requires more attention, as the increased floods may exceed the discharge capacity of the reservoir determined at the design stage.

Muhammad Rusdi, Meidi Wani Lestari, Yuvina et al.

Flood is an event of inundation of land, which is usually dry, by water originating from water sources around the land. Binjai City is an area prone to flash floods. This is because in Binjai City there are 5 (five) upstream rivers namely the Bingei river, Mencirim river, Bangkatan river, Diski river and Rambai river. A flood early warning system is a series of systems that function to notify an impending flood disaster. With the existence of a flood early warning system, it can provide information to the community and can reduce victims or losses due to the community's unpreparedness in dealing with flood disasters. This study aims to create a prototype of a river flood early warning system based on the internet of things (IoT). The method used is to design and create a flood early warning system prototype, then perform system testing. The system is designed using the Arduino Mega2560 microcontroller as the system control center, the HC-SR04 ultrasonic sensors and the ESP32-Cam camera module as system input, as well as buzzer, LCD and website as system output. The transmission medium used is wireless via a 4G WiFi Modem connected to the internet. System prototype testing will be carried out in the Bangkatan river area in Binjai City. From the results of the discussion, it was found that the river flood warning system using the HC-SR04 ultrasonic sensor and the ESP32-Cam camera module based on the Internet of Things was successfully designed and implemented in prototype form and worked well. Ultrasonic sensors work well in measuring river water level with an average error percentage of 3.642%. The ESP32-Cam camera module works well in capturing images of river water conditions up to a distance of 200 cm. (9 pt).

M R Mustamin, F Maricar, M P Hatta

Abstract The Nipa-Nipa Regulation Ponds are a flood control building for Makassar City and its surroundings due to the overflow of Tallo River downstream with an operating system to accommodate air. Regulation pond is only able to accommodate part of the peak flood discharge which caused Tallo River to overflow. For this reason, an analysis is carried out on how the influence of the Nipa – Nipa Regulation Pond on flood control of the downstream Tallo River is carried out. The analytical method used is a hydraulic analysis with the help of the HEC-RAS application. Based on the results of the 2D HEC – RAS numerical simulation mapped for the downstream area of Nipa - Nipa Regulation Pond, it is obtained that regulation can reduce surface runoff due to the overflow of the Lower Tallo River for Q2 by 183.97 Ha (35.59 %), Q5 271 .85 Ha (37.19 %), Q10 was 249.35 Ha (28.50 %), Q20 was 291.63 Ha (28.18 %), and Q25 was 300.67 Ha (28.08%). From these results, it can also be seen that the current condition of the Nipa – Nipa Regulation Pond is the most effective way to deal with flooding downstream of Tallo River at the five-year return period (Q5).

Ashleigh Massam, Helen Smith, Valeriya Filipova et al.

Abstract A novel approach to consider local‐scale defence infrastructure in an urban environment, coupled with a broadscale hydraulic model framework, is applied to the capital city of Kuala Lumpur, Malaysia. Broadscale hydraulic modelling frameworks are often able to employ more complex models, but are typically limited to homogenous decision‐making to ensure standardised outputs across large regions. Conversely, small‐scale hydraulic modelling frameworks tend to better integrate local‐scale features but can be computationally expensive to scale up beyond a regional view. Improvements to the broadscale hydraulic model framework through the incorporation of defence systems yield a more accurate representation of fluvial flood risk. This study incorporates defences in Kuala Lumpur, yielding a reduction in our estimates of fluvial flood extent by around 40%. The results of this study are validated against a set of high‐quality observations, demonstrating the capability of the model framework in capturing flood risk in more than 95% of known flood risk zones in the city. Incorporating defence infrastructure using data‐driven decision making and existing functionality in the hydraulic model could be automated in future model builds. This new approach bridges the gap between local‐scale model frameworks and the broadscale, homogenous 2D hydraulic modelling studies.

سعید چوپانی, پیمان رضائی, محمدرضا غریب رضا

مقدمهرودخانه­‌ها، سامانه­‌های بسیار تغییر­پذیر و یکی از مهمترین اکوسیستم­‌های آبی هستند که نقش مهمی در زندگی بشر و سایر موجودات زنده دارند و به سادگی تحت ­تاثیر آلودگی قرار می‌­گیرند. به­‌طور کلى، غلظت فلزات سنگین در رسوبات چندین برابر بدنه‌­هاى آبى است و فلزات سنگین در طى فرایندهاى طبیعى، تخریب و تجزیه نمی‌­شوند. بنابراین، فلزات سنگین می­‌توانند در رسوبات ذخیره شده و به مدت طولانى در آن باقى بمانند. به همین دلیل، رسوبات سطحى یکى از مخازن اصلى فلزات سنگین و سایر آلاینده­‌ها محسوب می­‌شوند. رودخانه کارون نیز از این آلودگی­‌ها مصون نمانده است و پساب­‌های بسیاری از صنایع فلزی، پتروشیمی و نفت، سلولزی و غذایی، فاضلاب­‌های خانگی، بیمارستانی و کشاورزی به این محیط آبی تخلیه می­‌شود. از سویی، این رودخانه تامین کننده آب برای این صنایع و منبع آب آشامیدنی برای شهرستان­‌هایی مانند اهواز، خرمشهر و آبادان است. ماهی­‌های این رودخانه بزرگ، یکی از منابع اصلی تغذیه مردم منطقه هستند که در نتیجه حضور آلاینده‌­ها به­‌خصوص عناصر بالقوه سمناک در کارون، می­‌تواند باعث آلودگی رسوب، آب و مواد غذایی شوند و چرخه حیات این رودخانه بزرگ را مورد آسیب قرار دهند. با توجه به گستردگی کمی و تنوع فعالیت‌­های انسانی در دشت خوزستان و ورود انواع پساب­‌ها و فاضلاب­‌ها به رودخانه کارون، بررسی آلودگی­‌ها، آلاینده­‌ها و سطوح مخاطرات ضرورتی اجتناب­‌ناپذیر است. لذا، این پژوهش با هدف تعیین میزان غنی­‌شدگی عناصر، تعیین خطر اکولوژیکی و مخاطره آمیز بودن آلودگی­‌ها در مقایسه با استانداردهای کیفیت رسوبات در رودخانه کارون در بازه ویس تا ابتدای شهر اهواز با استفاده از داده‌­های ژئوشیمیایی و تحلیل‌­های آماری انجام شده است.مواد و روش‌­هابه­‌منظور ارزیابی آلودگی رسوبات بستر رودخانه کارون، تعداد 22 نمونه با یک دستگاه شناور (قایق) از عمق صفر تا 10 سانتی­‌متری و بر مبنای روش­‌های رایج در زمین­‌شناسی رسوبی از رسوبات ریزدانه برداشت شد. سپس نمونه­‌ها در آزمایشگاه آب و خاک پژوهشکده حفاظت خاک و آبخیزداری، برای آزمون دانه‌­بندی و تعیین غلظت عناصر فلزی سمی آماده­‌سازی شدند. در نهایت، به­‌منظور بررسی وضعیت آلودگی رسوبات، غلظت­‌های به‌دست آمده با مقادیر استاندارد شاخص کیفیت رسوب (ISQGs)، سطح اثر شدید (SEL)، سطح اثرات احتمالی (PEL) و مقادیر پایه جهانی مقایسه شد.نتایج و بحثبر اساس نتایج به‌دست آمده از دانه‌بندی، رسوبات بستر رودخانه در بیشتر ایستگاه‌‎ها دارای بافت دانه­ ریز و از نوع گل، ماسه گلی و گل ماسه‌­ای و به‌طور میانگین، دارای 0.62 درصد ماده آلی هستند. نتایج سطح آلودگی نیز نشان داد که غلظت عناصر سمی آرسنیک (As)، نیکل (Ni) و کروم (Cr)، دارای مقادیری فراتر از مقادیر استاندارد ISQGs و PEL هستند. بر اساس مقایسه بین معیارهای کیفیت رسوب با استانداردها، رودخانه کارون در بازه مورد مطالعه دارای رسوباتی پاک از منظر عناصر Cd و Pb است. نتایج محاسبه عامل غنی­‌شدگی نشان داد که عنصر Zn، غنی‌­شدگی متوسط تا قابل توجه دارد. غنی­‌شدگی Cu، Ni و Cr در محدوده آلودگی متوسط قرار داشت. شبه فلز As، در محدوده غنی­‌شدگی کم تا متوسط و دو عنصر Cd و Pb، دارای غنی‌­شدگی کم هستند. میانگین غنی­‌شدگی عناصر به‌­ترتیب Zn>Ni>Cu>Cr>As>Pb>Cd است. بر اساس طبقه­‌بندی ژانگ و لیو، Cr، Ni، Zn، Cu و As، دارای منشا انسان‌­زاد و Pb و Cd منشا زمین­‌زاد دارند. در انتها، نتایج به‌دست آمده از شاخص خطر نشان داد که مقادیر شاخص خطر برای همه نمونه‌­ها در محدوده خطر کم (RI<150) قرار دارد. بررسی و تحلیل آماری بر روی نمونه‌­ها نشان داد که ارتباط معنی‌­دار مثبتی میانCr ، Ni، Cu و AS با رس وجود دارد. پس ذرات رس حامل اصلی عناصر Cr، Ni، Cu و As هستند. ضریب همبستگی بالا بین عناصر نشان از منبع مشترک، وابستگی متقابل و رفتار یکسان در طول حمل و نقل دارد.نتیجه‌گیریپژوهش حاضر منجر به شناخت کافی از وضعیت ژئوشیمیایی و هرگونه تغییر از شرایط طبیعی و آشکارسازی غنی‌شدگی موضعی و موضوعی سطح آلودگی­‌ها برای آبزیان و بهره­‌برداران به‌­ویژه حوزه کشاورزی و چرخه غذایی در رودخانه کارون در بازه ویس تا شهر اهواز شده است. نتایج عامل غنی­‌شدگی، آلودگی کم تا زیاد را برای عناصر انتخابی نشان دادند. مقادیر خطر بالقوه اکولوژیکی کلیه عناصر انتخابی به­‌جز As در نمونه 21، در محدوده خطر کم قرار دارند و AS در نمونه شماره 21 ( ساحل شرقی کیان پارس) در محدوده خطر متوسط قرار دارد. مقادیر شاخص خطر برای همه نمونه‌­ها در محدوده خطر کم قرار دارد. بر اساس مقایسه معیارهای کیفیت رسوب با استانداردها، رودخانه کارون دارای رسوباتی پاک از منظر عناصر Cd و Pb در بازه مورد مطالعه است. به‌طوری‌ که 100 درصد نمونه‌­ها غلظتی کمتر از ISQG دارند. میانگین غلظت شبه فلز سمی As، زیر کمینه سطح آلودگی ISQG است. Cr با 27 درصد و Ni با 100 درصد، دارای غلظتی فراتر از سطح آلودگی PEL و کلیه مقادیر به‌دست آمده برای عناصر Cr و Ni دارای غلظتی فراتر از غلظت کمینه سطح آلودگی ISQG است. بدین ترتیب، احتمال بروز مسمومیت برای آبزیان و بهره‌­برداری آب به‌وسیله عناصر سمی Ni و Cr وجود دارد. مقایسه غلظت عناصر با استاندارد­ها نشان داد که در ایستگاه­‌های شماره هفت (زیردست پرورش ماهی شیبان)، 21 (ساحل شرقی کیان پارس) و 10 (فاضلاب کورش)، عناصر Cr و Ni دارای غلظتی فراتر از سطح آلودگی PEL داشته و As  بیشتر از حداقل سطح ISQG بوده است و آلوده­‌ترین ایستگاه­‌ها در بازه مورد مطالعه هستند. به‌طوری ‌که در ایستگاه شماره هفت، حداکثر غنی­‌شدگی Cr و As هم اتفاق افتاده است. تحلیل خوشه‌­بندی عناصر نشان داد که مواد آلی حامل اصلی عنصر Cu و Zn و ذرات رس، حامل اصلی عناصر Ni و Cr هستند. همچنین، در مورد عناصر Cu و As نیز ذرات رس نقش اصلی را ایفا می­‌کنند. اما فلز سمی Pb، هیچ­گونه رابطه معنی‌داری با عناصر دیگر و همچنین مواد آلی و ذرات رس نشان نداده است. در نتیجه عنصر Pb دارای منشا متفاوتی نسبت به عناصر Cu، Zn، Cr، Ni و As است. نتایج تحلیل مولفه اصلی، ضمن تایید ضریب همبستگی و تحلیل‌ خوشه‌ای، در تایید عامل غنی‌­شدگی نشان داد که Cu، Zn، Cr، Ni و As منشا انسان­‌زاد دارند و عناصر Pb و Cd دارای منشا زمین­‌زاد هستند. این مطالعه سهم مهمی در تعیین منشا، آلودگی و خطر اکولوژیکی عناصر بالقوه سمناک دارد و می‌­تواند در شناخت منابع آلاینده و کنترل آلاینده‌­ها کمک کند.

Chuanying Hou, Y. Yi, Jie Song et al.

Abstract The Yellow River (YR) is famous for its high sediment concentration. The Xiaolangdi dam (XLD), the most downstream dam on the mainstream of the YR, plays an integral role in siltation mitigation, flood defence, agriculture, and hydropower generation. To alleviate siltation of the Xiaolangdi Reservoir (XLDR) and riverbed uplift of the lower reaches of the YR and strengthen flood control safety downstream, the XLDR began to implement water-sediment regulation in 2002. Water-sediment regulation (WSR) has significantly changed the hydrological processes, erosion and deposition, and sediment transport in the downstream channel, and the downstream water environmental conditions have also changed. In this study, 10 sections in the Lower Yellow River (LYR, from the XLDR to the Lijin section) and 4 sections in the soft floodplain area were sampled in the field to analyse their surface sediment grain size composition and nutrient content. At the same time, data on the average annual median particle sizes (D50) of channel sediments and suspended particles in 7 typical sections in the LYR from 2004 to 2015 were statistically analysed. The results show that the channel sediment grain size in the LYR decreased along the river course, and the D50 ranged from 0.20 mm in the HYK section to 0.08 mm in the LJ section. Moreover the D50 of the suspended sediment was less than 0.05 mm. The D50 of the channel and suspended sediment were both ranked as follows: non-flood season > flood season > WSR period. After WSR, fine silt particles with diameters of 0.01–0.05 mm were deposited on the soft floodplain. The channel sediment size was mainly coarse particles with diameters of 0.05–0.20 mm due to channel erosion. The suspension of fine silt particles due to flood scouring led to the total organic carbon (TOC) and total nitrogen (TN) absorbed in the particles to also be resuspended in the water. As a result, the TOC and TN contents in the channel sediments decreased by approximately 40% after WSR.

Sim M. Reaney

Abstract A wide range of nature‐based solutions for flood hazard management work by storing and slowing flow within catchments, and therefore, there is a need to identify the optimal locations for implementing these solutions. This paper presents a relative scoring‐based mapping of the likely locations that contribute to the flood peak. Targeting flow reduction and attenuating mitigation actions in these locations can be an effective way to reduce flood damages at impact points downstream. The presented tool, SCIMAP‐Flood, uses information on land cover, hydrological connectivity, flood generating rainfall patterns and hydrological travel time distributions to impacted communities to find the potential source areas of flood waters. The importance of each location in the catchment is weighted based on its contribution to the flood hazard at each of the downstream impact points. In the example application, SCIMAP‐Flood is applied at a 5‐m grid resolution for the River Eden catchment, Cumbria, England, to provide sub‐field scale information at the landscape extent. Therefore, the tool can identify sub‐catchments where more detailed work can test different mitigation measures.

Anna E. Sikorska‐Senoner

Abstract Hydrologic models are often employed in flood risk studies to simulate possible hydrologic responses. They are, however, linked with uncertainty that is commonly represented with uncertainty intervals constructed based on a simulation ensemble. This work adapts an alternative clustering‐based approach to first, learn about hydrological responses in the frequency space, and second, select an optimal number of clusters and corresponding representative parameters sets for a hydrologic model. Each cluster is described with three parameter sets, which enable percentile and prediction intervals to be constructed. Based on a small Swiss catchment with 10,000 years of daily pseudo‐discharge simulations, it was found that clustering the ensemble of 1000 members into 5–7 groups is optimal to derive reliable flood prediction intervals in the frequency space. This lowers the computational costs of using a hydrological model by 98%. The developed approach is suitable for probabilistic flood risk analysis with current or future climate conditions to assess hydrologic changes.

I. Echeverribar, P. Vallés, J. Mairal et al.

The vast majority of reservoirs, although built for irrigation and water supply purposes, are also used as regulation tools during floods in river basins. Thus, the selection of the most suitable model when facing the simulation of a flood wave in a combination of river reach and reservoir is not direct and frequently some analysis of the proper system of equations and the number of solved flow velocity components is needed. In this work, a stretch of the Ebro River (Spain), which is the biggest river in Spain, is simulated solving the Shallow Water Equations (SWE). The simulation model covers the area of river between the city of Zaragoza and the Mequinenza dam. The domain encompasses 721.92 km2 with 221 km of river bed, of which the last 75 km belong to the Mequinenza reservoir. The results obtained from a one-dimensional (1D) model are validated comparing with those provided by a two-dimensional (2D) model based on the same numerical scheme and with measurements. The 1D modelling loses the detail of the floodplain, but nevertheless the computational consumption is much lower compared to the 2D model with a permissible loss of accuracy. Additionally, the particular nature of this reservoir might turn the 1D model into a more suitable option. An alternative technique is applied in order to model the reservoir globally by means of a volume balance (0D) model, coupled to the 1D model of the river (1D-0D model). The results obtained are similar to those provided by the full 1D model with an improvement on computational time. Finally, an automatic regulation is implemented by means of a Proportional-Integral-Derivative (PID) algorithm and tested in both the full 1D model and the 1D-0D model. The results show that the coupled model behaves correctly even when controlled by the automatic algorithm.

Keisuke Yoshida, Kimihisa Nagata, S. Maeno et al.

Abstract This paper describes application of airborne LiDAR bathymetry (ALB) with near-infrared and green pulsed lasers for gathering distributed vegetation conditions and topo-bathymetric data for rivers. For the lower Asahi River of Okayama Prefecture in Japan, the ALB data validity was verified using field observation data. This study also examined the applicability of ALB data for numerical simulations of the lower Asahi River flooding in early July 2018 in Japan, comparing simulated and observed data. Results demonstrated that the methodology for this study works well for parameterization of distributed vegetation on a reach scale. This study also applied numerical tests to investigate the effects of vegetation establishment on flood control plans for the lower Asahi River using parameters validated for flood flow simulations. Results demonstrate that the predicted water level markedly exceeds the high water level because of thick vegetation presently established along few-kilometer-long upstream sections of the targeted river reach. Therefore, we conclude that the present findings can support cost-effective management tasks for vegetated rivers.

Yan Liu, Xinyu Lu, Yuanzhi Yao et al.

Abstract Mapping flood risk zone is an essential task in the arid region for sustainable water resources management. Due to the lack of hydrological and meteorological information and disaster event inventory in Xinjiang, China, storm flood disaster (SFD) risk zoning is an effective technique in investigating the potential impact of SFD. In this study, the statistics about natural, social, and risk related to SFD are collated. With the help of the compiled inventory data, a disaster risk assessment model for storm flood is proposed for the Xinjiang region based on the random forest (RF) algorithm. Randomly selected negative and positive samples from the historical SFD locations are composed of five different total samples. The overall prediction accuracy of the five sample groups attained 83.48%, indicating that the proposed RF model can well capture the spatial distribution of SFD in Xinjiang. It should also be noted that the spatial heterogeneity and complexity of SFD had a significant effect on its spatial distribution in Xinjiang. There are spatial distribution characteristics of lowland plains and high plateaus; the main mountainous regions, plains in the middle‐lower reaches of major rivers, and areas surrounding major lakes are prone to flooding. The variable importance RF indicates that the disaster risk is mainly affected by the following factors, including hazard factors, catastrophic intensity, population density, as well as economic development in the affected area. Besides, latitude, longitude, agricultural acreage, road density, distance from rivers, and the maximum monthly precipitation account for most of the increase in storm flooding disasters, and they are the main triggering point for SFD in Xinjiang. The proposed model provides some insight into the disaster in the mountainous region, and gives useful guidance for the national macro‐control of flood prevention and disaster reduction.