Summer Floods Research Articles

ВЛИЯНИЕ ВЕТРОВОГО АПВЕЛЛИНГА И СТОКА РЕКИ АМУР НА ТЕРМОХАЛИННУЮ СТРУКТУРУ ВОД У СЕВЕРО-ВОСТОЧНОГО ПОБЕРЕЖЬЯ ОСТРОВА САХАЛИН

The impact of the wind-driven upwelling and the Amur River discharge on the thermohaline water structure off the northeastern coast of Sakhalin was analyzed using hydrographic data аnd satellite information on the sea surface temperature distribution. The interaction of upwelling water and the coastal current depends on wind conditions and the Amur river runoff. Coastal upwelling develops at relatively low river runoff values (summer low water). The increase in the Amur River discharge during the summer flood enhances the interaction of the upwelling and the coastal buoyancy current. The Amur river runoff flows directly along the shore, which tears cold upwelling water off the coast. The advection of the cold upwelling water from the coast towards the open sea increases with the consecutive alternation of upwelling and downwelling events.

Effects of Low-Frequency Oscillation at Different Latitudes on Summer Precipitation in Flood and Drought Years in Southern China

Based on the daily precipitation data from 753 meteorological stations provided by the National Meteorological Information Center (China) and the daily reanalysis data from NCEP/NCAR and ERA5 during the period from 1980 to 2020, the low-frequency (LF) precipitation characteristics of the typical summer flood and drought years in southern China and their relation to the LF atmospheric circulation at different latitudes are compared and analyzed, and extended-range forecasting signals are given. The results show that: (a) In both flood and drought years, summer precipitation in southern China is controlled by 10–20 day oscillation (quasi-biweekly oscillation, QBWO); (b) LF convection is active in southern China in both flood and drought years, but the convective center is southward in flood years, and the vertical meridional circulation is stronger. The key circulation systems of 500 hPa LF height field in flood and drought years include LF “two ridges and one trough” and LF “+”, “−”, “+” East Asia Pacific (EAP) teleconnection wave train in mid-high latitudes of Eurasia. However, the “two ridges and one trough” in flood years are more westward and meridional than in drought years, and the LF Subtropical High is stronger and more extensive, with more significant westward extension; (c) In flood (drought) years, there is northerly and then westerly (central westerly) dry-cold, northeasterly wet-cold, southwesterly (none), and southeasterly (including southerly across the equator) wet-warm water vapor channels. The sources of dry and wet cold air in flood (drought) years are located near Novaya Zemlya (the eastern West Siberian Plain), the Yellow Sea, and the Bohai Sea (Sea of Japan). Additionally, the sources of wet-warm water vapor include the Arabian Sea, the Bay of Bengal, the western Pacific Ocean, and the sea area of northeastern Australia (the western Pacific Ocean and the northern sea area of Australia); and (d) The LF predictive signals of outgoing longwave radiation (OLR) appear on −11 days, while the signals of the 500 hPa height field are on −9 days. There are both westward and eastward propagation predictive signals in flood years, and only westward spread signals in drought years.

Study of the Relationship between High Mountain Asia Snow Cover and Drought and Flood in the Yangtze River Basin during 1980–2019

High Mountain Asia (HMA), with its high altitude, widely distributed snow and frozen soil, influences the climate of the northern hemisphere and even the world through thermal balance and the water vapor cycle and is also an indicator of global climate change. The influence of HMA snow cover on its surrounding areas has always been a research hotspot. Taking the Yangtze River Basin (YRB) of China as an example, this paper analyzes the relationship between winter snow depth in HMA and drought and flood in spring and summer in the YRB in the recent 40 years by using Singular Value Decomposition (SVD). The results show that the influence of snow cover on drought and flood in spring is inversely different between eastern and western parts of HMA, while the effect in summer is consistent. When the snow depth is larger (smaller) in the east and smaller (larger) in the west in winter, the YRB is drier (wetter) in spring. When the overall snow depth in HMA is larger (smaller) in winter, the northern part of the middle and lower reaches of the YRB is drier (wetter) in summer. The results provide support for understanding the impact of HMA snow cover on the surrounding climate and some important indicators for drought and flood prediction in the YRB.

Radium Isotopes and Nutrients in Razdolnaya River Estuary (Amur Bay, the Sea of Japan) in the Period of Summer Flood

Radium Isotopes and Nutrients in Razdolnaya River Estuary (Amur Bay, the Sea of Japan) in the Period of Summer Flood

Assessing landscape fragmentation in a desert-oasis region of Northwest China: patterns, driving forces, and policy implications for future land consolidation.

Landscape fragmentation is considered a serious threat to eco-environmental integrity and socioeconomic development. Although many studies have focused on landscape fragmentation resulting from agricultural production and urbanization, landscape fragmentation from the aspects of patterns, driving forces, and the policy perspective of ecosystems has rarely been investigated. Oases, as a unique landscape, face severe fragmentation in arid and semiarid regions. This study applied a combination of approaches, including remote sensing image interpretations, landscape fragmentation metrics, and community surveys, to analyze patterns and their driving forces, as well as the policy implications for future land consolidation, in the Hotan oasis of Northwest China from the space and time perspectives. Results show that the frequent occurrence of summer flood events changes the patch number, density, size, and splitting degree of oasis-desert ecotone vegetation. The socioeconomic factors including total population and irrigation area are more important driving forces on oasis landscape fragmentation, compared with natural factors such as temperature and precipitation. Rural expansion, road and canal system developments caused by population growth, and the rising number of households increase oasis landscape fragmentation. Rapid economic development, such as agricultural expansion and urbanization, has imposed the intensification of landscape fragmentation. Fragmentation reaches peak when agricultural development makes up 40-50% of study area. Rural residential reconstruction and farmland transfer policies facilitate the intensive utilization of land toward oasis fragmentation solutions, but many factors, such as landholders' household characteristics and living conditions, are partly responsible for the challenges in land consolidation. This study also demonstrates that intense human activities pose a great threat for land consolidation and sustainable development of oasis landscape.

Moisture sources of heavy precipitation in Central Europe in synoptic situations with Vb-cyclones

During the past century, several extreme summer floods in Central Europe were associated with so-called Vb-cyclones propagating from the Mediterranean Sea north-eastward to Central Europe. The processes intensifying the precipitation in synoptic situations with Vb-cyclones in the Danube, Elbe, and Odra catchments are only partially understood. Our study aims to investigate these processes with Lagrangian moisture-source diagnostics for 16 selected Vb-events. Moreover, we analyse the characteristics of typical moisture source regions during 1107 Vb-events from 1901 to 2010 based on ERA-20C reanalysis dynamically downscaled with COSMO-CLM+NEMO. We observe moisture contributions by various source regions highlighting the complex dynamical interplay of different air masses leading to moisture convergence in synoptic situations with Vb-cyclones. Overall, up to 80% of the precipitation originates from the European continent, indicating the importance of continental moisture recycling, especially within the respective river catchment. Other major moisture uptake regions are the North Sea, the Baltic Sea, the North Atlantic, and for a few events the Black Sea. Remarkably, anomalies in these oceanic source regions show no connection to precipitation amounts in synoptic situations with Vb-cyclones. In contrast, the Vb-cyclones with the highest precipitation are associated with anomalously high evaporation in the Mediterranean Sea, even though the Mediterranean Sea is only a minor moisture source region on average. Interestingly, the evaporation anomalies are not connected with sea-surface temperature but with wind-speed anomalies (Spearman’s rank correlation coefficient Rapprox 0.7, significant with p<0.01) indicating mainly dynamically driven evaporation. The particular role of the Mediterranean Sea hints towards possible importance of Mediterranean moisture for the early-stage intensification of Vb-cyclones and the pre-moistening of the continental uptake regions upstream of the target catchments.

Spatiotemporal dynamics of dissolved organic carbon in a subtropical wetland and their implications for methane emissions

Wetlands represent about one-third of the global soil organic carbon storage and are the largest natural source of atmospheric methane, a powerful greenhouse gas. Understanding the factors that influence the carbon dynamics in wetlands, and their influence on methane emission, is therefore important. Dissolved organic carbon (DOC) is a major form of carbon export from wetlands and plays an essential role in the aquatic carbon cycling process. However, constraints on spatial and temporal dynamics of DOC in vertical peat layers and their relationship to wetland methane emissions are still rare. Here we investigated spatiotemporal changes in porewater DOC concentration and optical properties (SUVA254, E2/E3, E4/E6) in surface (0–10 cm) and deep (20–30 cm, 50–60 cm, 100–110 cm) peat layers in a subtropical wetland complex, central China, with the aim to explore DOC dynamics and their relationship to methane emissions from wetlands. DOC dynamics and environmental controls were investigated in the context of high-resolution environmental monitoring, including air temperature, rainfall, water table depth, water chemistry, and methane emissions. DOC of surface peat layers generally had higher concentrations, higher aromaticity, lower humification, and greater temporal variations compared to deeper peat layers. During summer floods and high water table conditions, DOC concentrations in the surface peat increased significantly, whilst DOC exports from rivers and lakes also increased synchronously. In contrast, DOC concentrations and spectral properties of deep peat layers remained constant across the sampling months and water table fluctuations. Methane emissions were positively correlated with air temperature and DOC concentration in the porewater of surface peat layers, and negatively correlated with water table depth. Our results suggest that DOC concentration in the porewater of surface peat layers may also have affected the flux of methane emission from wetlands.

The Status of the Riparian Forests in the Naryn Valley of Kyrgyzstan: Conservation and Sustainable Development

Conservation and restoration of riparian forests are important for strengthening river banks and preserving biodiversity as well as for mitigating impacts of climate change. Increasing temperature and climate variability, flooding and drought, alteration of the intensity of precipitation and melting glaciers in high mountain areas affect the physical condition of natural resources as well as natural hazards. Climate change might cause larger and potentially hazardous summer floods. The temporary storage of floodwaters in the floodplain areas reduces the flood risk downstream. In this paper, the current state of natural resources and the benefits of mountain floodplain forests is investigated. The satellite imagery was used to study the landscape changes for mapping the investigation areas. The assessment of changes is necessary for the further development of restorative plan for floodplain rivers. The results provide information on options for management and provide assistance to the local authorities engaged in the integrated management of natural resources.

Should I stay or should I go: Hydrologic characteristics and body size influence fish emigration from the floodplain following an atypical summer flood

AbstractFloods play an important role in regulating ecological patterns and processes in river–floodplain ecosystems. Yet, the hydrologic connectivity between many river–floodplain ecosystems has been severed by anthropogenic activities that have markedly altered these ecological processes. Superimposed over anthropogenic reductions in river–floodplain connectivity, climate change is also shifting flood characteristics to produce more intense, unpredictable floods. To more efficiently manage river–floodplain ecosystems, additional research characterising the ecological consequences of unpredictable floods on fish movements is required. In this study, we used a modified fyke net to characterise the patterns and identify the important drivers of lateral movements of fish emigrating from the floodplain during contraction of a high‐magnitude, late‐summer flood in the Fourche LaFave River, Arkansas, in 2007. We captured approximately 43,200 fish emigrating from the floodplain over an 8‐day period, representing 38 distinct species from 12 families. We related fish‐emigration patterns to different stages of flood contraction and linked species‐specific emigration to water‐level fluctuations and associated changes in floodplain habitat availability and quality. We also show that some species exhibit body‐size emigration patterns, where larger individuals emigrated from the floodplain earlier than smaller individuals. To meet conservation goals for maintaining healthy riverine ecosystems and the biodiversity they support, it will be necessary to continue characterising and identifying the ecological consequences of shifting flood characteristics within river–floodplain ecosystems.

Nonstationary streamflow effects on backwater flood management of the Atchafalaya Basin, USA

A non-stationary increasing streamflow trend has been observed on the Mississippi River and other major river basins around the world. The current study analyzed the non-stationary streamflow effects (NSFEs) on flood management in backwater areas adjacent to the Atchafalaya Basin floodway in Louisiana, USA. A continuous simulation hydrology model coupled with a quasi-two-dimensional hydrodynamic model of the basin floodway and surrounding regions was used to develop over 180 simulation scenarios by superimposing local flood events (early summer 2014 and late summer 2016) against 90-years’ worth of daily Atchafalaya River streamflow hydrographs. The NSFE on the Atchafalaya River induced substantial reductions in the performance of major flood regulating structures with seasonal effects based on the annual flood cycle. Capacity reductions at the structures were demonstrated to trigger a cascade of effects in ostensibly protected backwater areas including amplification of erosion potential near the levee and within tidal passes during early summer floods. Increases in mean and peak flood levels on the order of 15–20 cm during local storm events were shown to extend as far as 20 km away from the floodway protection levee during both early and late summer local flooding scenarios. Low-lying areas closest to the levee were adversely affected during both the high (early summer) and low flow (late summer) periods of the annual discharge cycle. The approach and findings of this study are relevant for risk management in river basins around the world affected by NSFEs.

Hydrological alteration and biodiversity change along the river network caused by anthropogenic activities and climate variability

BackgroundPopulation growth and intensified human activities in conjunction with climate variability continue to affect the hydrologic cycle, aquatic and terrestrial flora and fauna. In this regard, understanding interactions among ecosystem functions, impacts of anthropogenic interventions and those of climate variability is vital for projecting future ecosystem responses to human activities and climate forcing. The objectives of this study are to determine the ecological flow state via eco-flow index based on discharge hydrograph, to model the ecological diversity through the Shannon diversity index, and to assess the degree of hydrologic alteration using indicators of hydrologic alteration and range of variability approach in six hydrometric stations along the Zayandeh-Rud River in central Iran. The river drains into Gavkhuni Marsh. Also, the streamflow-induced potential changes for Capoeta damascina (a cyprinid fish species of the genus Capoeta), Petroleuciscus esfahani (a small cyprinid fish) and Aphanius isfahanensis (a Cyprinodontid fish) are evaluated. The outcome is expected to assist managers with understanding the effects of anthropogenic activities and climate variability on Gavkhuni aquatic ecosystems so that management options that enhance species resilience and adaptability are outlined.ResultsHuman activities, a primary factor influencing the natural flow regime, caused a significant increase in the minimum flow, July to March streamflow, low pulse number, and the number of reversals in most studied stations. On the contrary, some other hydrologic indices declined in value. Reservoir impoundment, the most prominent factor among human interventions, resulted in an overall alteration degree of 74.8% in streamflow. Climate variability impacted the natural flow regime in the range of low degree hydrologic alteration (27.3%). In addition, the biodiversity of the study basin, as modeled by the Shannon diversity index, had strong relevance to the annual eco-surplus and was more sensitive to summer floods and autumn hydrological droughts than other factors.ConclusionsThis study corroborates the effectiveness of scenario-based hydrological modeling framework in evaluating the impacts of climate variability and human activities imposed on natural flow metrics. Additionally, the recently introduced eco-flow metrics based on discharge hydrographs and the Shannon diversity index based on indicators of hydrological alteration may be adopted in basins lacking ecological data. These two indices can effectively identify the most prominent factors in hydrological alteration and biodiversity change through a river network and may provide scientific decision-making support for water resource management in the study area.

A New Kind of Salvage: The Emergency Container of Cologne

ABSTRACT The Cologne Emergency Association of Archives and Libraries’ roll on/ off container represents an innovative approach to salvaging collections affected by disasters. Designed in close cooperation with the Cologne Fire Brigade, the container provides both workstations for documentation, cleaning and preparing for freezing along with storage for most required materials and equipment. This allows for on-site salvage and processing of objects to begin almost immediately in all weathers upon the delivery of the container. This article details the project’s background and conception, a description of the container’s features and its intended use. The final section covers the container’s first salvage operation in the town of Stolberg, Germany in the wake the terrible floods in summer 2021 and the future developments planned.

Characterizing the 2020 Summer Floods in South China and Effects on Croplands

Characterizing the 2020 Summer Floods in South China and Effects on Croplands

Исследование берегоукрепительных сооружений на р. Куме в Ставропольском крае

Purpose: substantiation of the required width of a stable channel while carrying out bank protection works on the Kuma river near the town Zelenokumsk Stavropol Territory. The analysis of the river feeding conditions in the design area is carried out, the main reasons for the erosion-accumulative processes of the Kuma river in the central part of Zelenokumsk, Stavropol Territory are considered. Materials and methods. The considered basin of the Kuma river is located in two natural zones – the foothills of the North Caucasus and the steppes of the Ciscaucasia, that affects the stable groundwater feed and the flood regime in the warm season due to heavy rainfall. Spring flood is not observed here due to the gradual snow melting along the high-altitude zones, therefore, there is a gradual transition from the winter runoff low period to the high-water-flood period. As a result of double feeding, the originality of the water regime of the Kuma basin rivers is formed, in which spring floods, multi-peak summer floods and a stable autumn-winter low-water period are combined. Results. The width of the stable channel was checked by Altunin's recommendations, and the fastening options based on the available morphometric characteristics were assigned. Conclusions. The gabion structure has an excellent quality of stability, that is, the structure can help the plant fixation or the vegetation reproduction within the structural frame. Root growth actually helps the structure to become more stable. Consequently, the operation process of such structures improves the ecosystem. Besides, the gabion construction regulates the environment in terms of climate and humidity. A good design can effectively regulate the velocity of the flowing water, increasing the roughness, thus minimizing the probability of flooding.

Species diversity, spatial distribution and protection strategies of wintering waterbirds after extreme summer flood in Lake Poyang

鄱阳湖是我国最大的淡水湖，也是具有国际意义的候鸟越冬地. 近年来，鄱阳湖水文情势异常使得候鸟越冬环境更加复杂. 本文以2020年鄱阳湖出现夏季极端水位为背景，基于2019和2020年鄱阳湖越冬水鸟同步调查数据，探讨了夏季极端水位对越冬水鸟丰富度和空间分布的影响. 研究结果表明：夏季极端水位条件下鄱阳湖越冬水鸟的总数量、群落结构和优势物种组成相对稳定，水鸟数量由597307只下降至572358只，主要是鸭科、鸥科、鹳科、鸬鹚科和鹮科鸟类数量明显下降；食块茎、食种子和食鱼集团水鸟数量均有所下降. 水鸟的整体空间分布格局变化不大，主要栖息地仍为鄱阳湖保护区和上饶湿地的碟形湖及人控湖汊，越冬水鸟向人工湿地扩散加剧. 2019年在人工湿地主要记录到灰鹤926只、白鹤3只；2020年则记录到白鹤2215只、灰鹤7294只、白头鹤88只、白枕鹤378只、豆雁550只、鸿雁3100只、灰雁3200只和小天鹅1543只. 2020年冬季人工湿地中的越冬水鸟数量比2019年增加显著. 鄱阳湖夏季极端水位导致沉水植物群落崩溃，造成植食性水鸟在天然湿地中的越冬食物短缺，从而导致种群空间分布格局出现明显变化，这也是鹤类和雁类水鸟前往人工湿地觅食的主要原因. 因此，在夏季洪水频发的背景下加强人工湿地管理，是当前解决越冬水鸟天然湿地食物资源短缺的重要措施.;Lake Poyang is the largest freshwater lake in China and has been an important wintering ground for migratory birds. In recent years, the abnormal hydrological regime of Lake Poyang deteriorated the quality of this wintering ground for migratory birds. In summer of 2020, Lake Poyang experienced extreme water level, which maybe affect the waterbird community structure and waterbird distribution. We compared the wintering waterbird species diversity, abundance and spatial distribution between winter of 2019 and 2020 to understand the impact of extreme water level on wintering waterbirds. The results showed that the total number, community structure and dominant species composition of wintering waterbirds were relatively stable after extreme summer water level. The total number of waterbirds decreased from 597307 to 572358, among which the number of Anatidae, Laridae, Ciconiidae, Phalacrocoracidae and Threskiornithidae obviously decreased. The abundances of tuber eaters, seed eaters and fish eaters were declined. The overall spatial distribution pattern of waterbirds showed little change. Waterbirds mainly inhabited the sub-lakes and controlled lake branches in the Lake Poyang National Nature Reserve and Shangrao wetland. However, waterbirds spread more severely from Lake Poyang nature wetlands to artificial wetlands nearby Lake Poyang. In 2019, 926 common cranes and 3 Siberian cranes were recorded in rice paddies and lotus ponds; In 2020, 2215 Siberian cranes, 7294 common cranes, 88 hooded cranes, 378 white-napped cranes, 550 bean geese, 3100 swan geese, 3200 greylag geese and 1543 tundra swans occurred in these artificial wetlands. The wintering waterbirds in artificial wetlands in winter of 2020 was significantly more abundant than that in winter of 2019. The extreme water level in summer led to the collapse of submerged plant community, resulting in the shortage of wintering food for herbivorous waterbirds in the natural wetlands, which drove cranes and geese dispersed into the artificial wetlands. Therefore, it is necessary to strengthen the management of artificial wetlands under the condition of frequently higher flood in Lake Poyang for wintering waterbirds conservation.

Количественные характеристики зообентоса бассейна озера Удыль (заказник «Удыль», Хабаровский край)

The article reports the results of the study on zoobenthos in the wetlands of Lake Udyl and its 12 tributaries (the Lower Amur, Udyl Nature Reserve) during the 2021 summer flood. Except for the Bichi River, benthic communities of the rivers and streams in the Lake Udyl basin were studied for the first time. The study found that the composition, structure and quantitative characteristics of the bottom communities of Udyl Lake and the Bichi salmon river differed from the previous results obtained in the 1930s–1940s and the 1990s. The results revealed a rich taxonomic composition of invertebrates (19 groups), low values of density and biomass in the water bodies of the reserve. The zoobenthos was dominated by amphibiotic insects (57% of the total density and 43% of the total biomass). We established that oligochaetes and chironomids in the Udyl Lake basin differed in the highest quantitative indicators. The quality of water was determined using classical (GW, TBI, IB, ND/Nex, NCh/Nex) and modified (IPM, TBIM) bioindicative indices and metrics. The results show that, in general, the ecosystem of Lake Udyl and the watercourses flowing into it is in a relatively satisfactory condition.

ميكانزمات واحتمالات نشأة الفيضانات المتطرفة بالمناطق الجافة (سهل تزنيت - المغرب)

يشهد تردد وعنف الظواهر الهيدرولوجية والمناخية المتطرفة التي تؤدي إلى حدوث فيضانات غامرة. يهدف هذا البحث إلى دراسة الخصوصيات والميكانزيمات المتحكمة في نشأة الفيضانات التي شهدها الحوض النهري لواد أودودو (إقليم تزنيت – المغرب الجنوب الغربي) وإجراء تحليل ترددي للأحداث الهيدرولوجية المتطرفة المرتبطة بالفيضانات من أجل تقدير فترة عودة حدوثها، فضلا عن تشخيص العوامل الطبيعية بمجال الدراسة وفهم الآليات الطبيعية وعلاقتها بنشأة الفيضانات، تعتمد الخطوات المنهجية مقاربتين: مقاربة تاريخية وأخرى إحصائية. تقوم الأولى على دراسة 8 حالات فيضانات عرفتها سافلة الحوض (المجال الحضري لمدينة تزنيت وجماعة أكلو)، وتحديد وتصنيف الأحياء والدواوير المهددة بالفيضانات من خلال الشهادات والمعاينات المباشرة للساكنة المجاورة. أما الثانية فركزت على تحليل ترددات الأحداث الهيدرومناخية القصوى (frequency analysis of hydroclimatic extreme events) لتصنيفها وتحديد خطورتها وفترة عودة وقوعها. يتضح من خلال تحليل النتائج المتحصل عليها، وجود ترابط دائم بين عتبات الفيضانات وقوة التساقطات المطرية وتركزها في الزمان والمكان، مما يعطيها سلوكا فجائيا شبيها بالفيضانات الصيفية والخريفية. مكنت هذه الدراسة من تحديد المناطق المهددة بالفيضانات وتصنيفها حسب درجة الخطورة، عبر العمل الكرطوغرافي بهدف توجيه تدخلات الفاعلين في الميدان. فقد مكن تحليل قيم الصبيب باستخدام نموذج تحليل الترددات واحتمالات حدوث الأحداث الهيدرومناخية الشديدة (فيضانات) وكذلك حساب قيم الصبيب اللحظي التي توافق فترات العودة من 2، 5، 10، 20، 50 و100 سنة. فالأحداث الهيدرولوجية ثنائية وخماسية الحول تتوافق مع تدفقات لصبيب لحظي من 120 إلى 331 متر3/ ثانية، في حين ان الحالات الاستثنائية والاستثنائية جدا، لها فترة عودة تزيد عن 50 و100 سنة وتتوافق مع تدفقات لصبيب لحظي من 912 إلى 1035 متر3/ ثانية.

Flood Detection Using Multiple Chinese Satellite Datasets during 2020 China Summer Floods

Multiple source satellite datasets, including the Gaofen (GF) series and Zhuhai-1 hyperspectral, are provided to detect and monitor the floods. Considering the complexity of land cover changes within the flooded areas and the different characteristics of the multi-source remote sensing dataset, we proposed a new coarse-to-fine framework for detecting floods at a large scale. Firstly, the coarse results of the water body were generated by the binary segmentation of GF-3 SAR, the water indexes of GF-1/6 multispectral, and Zhuhai-1 hyperspectral images. Secondly, the fine results were achieved by the deep neural networks with noisy-label learning. More specifically, the Unet with the T-revision is adopted as the noisy label learning method. The results demonstrated the reliability and accuracy of water mapping retrieved by the noisy learning method. Finally, the differences in flooding patterns in different regions were also revealed. We presented examples of Poyang Lake to show the results of our framework. The rapid and robust flood monitoring method proposed is of great practical significance to the dynamic monitoring of flood situations and the quantitative assessment of flood disasters based on multiple Chinese satellite datasets.

Nitrogen isotope constraint on the zonation of multiple transformations between dissolved and particulate organic nitrogen in the Changjiang plume

Information on the sources and transformations of particulate organic N (PN) and dissolved organic N (DON) at the coastal interface remains insufficient due to technological difficulties and complicated features of intensive physical mixing and rapid biological activities. Here, we investigated the spatial distribution of concentrations and isotopic compositions of PN and DON in the Changjiang plume during the summer flood period. In average, DON and PN accounted for 25.6 ± 12.1% and 8.1 ± 9.1% (n = 55), respectively, of the total N pool, with the remaining N primarily in the form of nitrate (NO3−). Mean δ15N values were the lowest for DON (−0.1 ± 2.7‰, n = 58) and slightly higher for PN (2.0 ± 1.6‰, n = 101), and the highest for NO3− (6.5 ± 2.2‰, n = 67), suggesting multiple transformations had occurred to differentiate isotopic characteristics among the three N pools. By applying a conservative mixing model, we found DON deficits (−3.5 ± 3.7 μmol L−1, n = 43) and negative shift in δ15NDON (−3.6 ± 2.2‰, n = 43) in the Changjiang plume, revealing nonconservative DON behaviors. In the offshore surface plume where Chlorophyll a was high, the most likely cause is the DON uptake by phytoplankton with a strong inverse isotope effect (around −40‰). This DON assimilation by phytoplankton contributed to ~16 ± 12% of the PN production, with the remaining supported by NO3− assimilation, producing an overall isotope effect of 4–9‰. However, in waters near the river mouth and at the bottom of the offshore plume where total suspended matter concentrations were high (>5 mg L−1), the DON deficit was most likely induced by the selective adsorption of 15N enriched moieties of DON onto particulate surfaces (with an isotope effect of −20‰ to −5‰). Unlike dissolved organic carbon to behave conservatively in most estuaries, our results show that active transformations had occurred between the DON and PN pools in the Changjiang plume.

Disaster Flood Scenario: Case Study of the Uh River at Lekárovce (Slovakia)

The occurrence of extreme floods in several river basins of the countries of Central and Eastern Europe over the last thirty years has drawn the attention of the public (as well as the competent authorities) to the problems of flood protection. Although the development and operational use of non-structural measures (such as flood forecasting and warning systems), represents one of the effective flood protection measures, the structural means (flood protection, levees, flood control reservoirs) are of great importance, too. Especially in the upper parts of the river basin, where the time between the detection of the causes of the flood (heavy rainfall) and its consequence (flood) is short and does not affect the effective protective activity (e.g. evacuation). Over the last 30 years, flood protections have been built along the Uh River (Slovakia, Ukraine) to protect the environment from floods. These dams adversely affected the storage capacity of water in the basin. This resulted in flood flows increase on the lower sections of the Uh River in Slovakia. These facts need to be demonstrated by the need to evaluate the proposed design values for those sections. The study presents an analysis of the long-term flood regime of the river Uh in the section Uzhhorod (Ukraine) - Lekárovce (Slovakia). The first part analyses the trend changes in the time series of maximum annual discharge Qmax in the stations Lekárovce and Uzhhorod on the basis of the observed Qmax data in these profiles (period 1931-2019). These Qmax series were subsequently used to estimate the maximum T-year discharge at the Lekárovce station for the changed conditions of the Uzhhorod - Lekárovce section. Using these derived data and the observed form of the summer flood hydrograph from July 1980, a 100-year flood scenario was developed for the Uh River in Lekárovce. The achieved results indicate a further increase in flood risk in Lekárovce.