River Flood Events Research Articles

A comparative study of optical and size properties of dissolved organic matter in the lower Mississippi River and Pearl River

Monthly water samples were collected from the lower Mississippi and Pearl Rivers between January 2009 and August 2011 to investigate the heterogeneity in the dynamic variations of dissolved organic carbon (DOC), colloidal organic carbon, chromophoric and fluorescence dissolved organic matter (CDOM and FDOM), PARAFAC-derived fluorescent components, and other optical properties including spectral slope, specific UV absorbance (SUVA), and fluorescence indices between the two contrasting river systems. The lower Mississippi River exhibits relatively lower concentrations of DOC (306 ± 41 μM C) and CDOM (27.9 ± 5.7 m−1 at 254 nm), featuring lower aromaticity (indicated by SUVA254) and apparent molecular weight (or higher spectral slope) with weak seasonal variability. The Pearl River, in contrast, has elevated levels of DOC (537 ± 212 μM C) and CDOM (66.4 ± 31.4 m−1), characterized by higher aromaticity, higher molecular weight, and significant seasonality, primarily originating from soil-derived allochthonous sources. The abundance of the >1 kDa colloidal DOC was, on average, 58 ± 3 % of the bulk DOC in the lower Mississippi River and 68 ± 6 % in the lower Pearl River. The >1 kDa high-molecular weight DOM (HMW-DOM) consistently had lower spectral slope and biological index (BIX) values, but higher humification index (HIX) values compared to both bulk DOM and low-molecular-weight DOM (LMW-DOM) counterparts. These trends could be representative of other similar large and small rivers. Four PARAFAC-derived fluorescent components (three humic-like and one protein-like) were identified for both rivers. A positive correlation between discharge and terrestrial humic-like fluorescent components indicated their dominant allochthonous sources, while the protein-like component decreased with increasing discharge, consistent with its autochthonic source and a dilution effect during high flow seasons. The occurrence of large flood events during the sampling period contributed to large DOC pulses, with DOM of higher aromaticity and HMW-DOM. This has important implications for coastal ocean ecosystems, which are increasingly impacted by river flooding events under changing climate conditions. Our results also provide an improved understanding of DOM dynamics in two representative rivers and establish a baseline dataset for future studies to assess changes in sources and composition of DOM and their impacts on the coastal ocean in response to climate, hydrological, and anthropogenic influences.

Contaminant mobilization from the vadose zone to groundwater during experimental river flooding events

Natural river flooding events can mobilize contaminants from the vadose zone and lead to increased concentrations in groundwater. Characterizing the mass and transport mechanisms of contaminants released from the vadose zone to groundwater during these recharge events is particularly challenging. Therefore, conducting highly-controlled in-situ experiments that simulate natural flooding events can help increase the knowledge of where contaminants can be stored and how they can move between hydrological compartments. This study specifically targets uranium pollution, which is accompanied by high sulfate levels in the vadose zone and groundwater. Two novel experimental river flooding events were conducted that utilized added non-reactive halides (bromide and iodide) and 2,6-difluorobenzoate tracers. In both experiments, about 8 m3 of traced water from a nearby contaminant-poor river was flooded in a 3-m diameter basin and infiltrated through the vadose zone and into a contaminant-rich unconfined aquifer for an average of 10 days. The aquifer contained 13 temporary wells that were monitored for solute concentration for up to 40 days. The groundwater analysis was conducted for changes in contaminant mass using the Theissen polygon method and for transport mechanisms using temporal moments. The results indicated an increase in uranium (21 and 24%), and sulfate (24 and 25%) contaminant mass transport to groundwater from the vadose zone during both experiments. These findings confirmed that the vadose zone can store and release substantial amounts of contaminants to groundwater during flooding events. Additionally, contaminants were detected earlier than the added tracers, along with higher concentrations. These results suggested that contaminant-rich pore water in the vadose zone was transported ahead of the traced flood waters and into groundwater. During the first flooding event, elevated concentrations of contaminants were sustained, and that chloride behaved similarly. The findings implied that contaminant- and chloride-rich evaporites in the vadose zone were dissolved during the first flooding event. For the second flooding event, the data suggested that the contaminant-rich evaporites continued to dissolve whereas chloride-rich evaporites were previously flushed. Overall, these findings indicated that contaminant-rich pore water and evaporites in the vadose zone can play a significant role in contaminant transport during flooding events.

Numerical modelling of pore water pressure response beneath a raft foundation during real river floods

Tall buildings with basement levels are increasingly being built due to need for space in large cities. Frequently, such structures are built involving a raft foundation and diaphragm walls below the water table. In addition, sometimes such buildings are located on floodplains. Therefore, if a river flood event occurs, the building can be exposed to pore water pressure (due to the fluctuation of water table) acting beneath its raft foundation. The generated subpressures will depend on the water table changes with time, and on the way such pressures are transmitted through the ground. Previous works have studied this behavior through laboratory and small-scale tests or numerically; however, many of them have used a constant hydraulic gradient and the water table fluctuations with time have been ignored. In this work, the evolution of pore water pressures with time mobilized beneath a raft foundation of a building built in a floodplain is studied. To do that, full-scale numerical models capable of simulate a river flooding and its corresponding overflow are developed. Such models incorporate data from water table change–time curves recorded during real river floods associated with a set of river regimes. Additionally, the effect of factors such as the soil permeability, the diaphragm wall length, and the soil thicknesses on water pore pressures beneath a raft foundation are also analyzed. Results suggest numerical models developed herein are capable of reproducing pore pressures induced beneath a raft foundation during river flooding. Furthermore, it was found that the above-mentioned factors could impact the percentage of pore water pressure mobilized beneath the raft foundation with respect to the maximum pore water pressure that could be induced during river flooding, and that the principal risk arises in buildings near large catchments where the flow increases over an extended period. Finally, practical implications and recommendations to practitioners are provided.

Assessing downscaling methods to simulate hydrologically relevant weather scenarios from a global atmospheric reanalysis: case study of the upper Rhône River (1902–2009)

Abstract. We assess the ability of two modelling chains to reproduce, over the last century (1902–2009) and from large-scale atmospheric information only, the temporal variations in river discharges, low-flow sequences and flood events observed at different locations of the upper Rhône River catchment, an alpine river straddling France and Switzerland (10 900 km2). The two modelling chains are made up of a downscaling model, either statistical (Sequential Constructive Atmospheric Analogues for Multivariate weather Predictions – SCAMP) or dynamical (Modèle Atmosphérique Régional – MAR), and the Glacier and SnowMelt SOil CONTribution (GSM-SOCONT) model. Both downscaling models, forced by atmospheric information from the global atmospheric reanalysis ERA-20C, provide time series of daily scenarios of precipitation and temperature used as inputs to the hydrological model. With hydrological regimes ranging from highly glaciated ones in its upper part to mixed ones dominated by snow and rain downstream, the upper Rhône River catchment is ideal for evaluating the different downscaling models in contrasting and demanding hydro-meteorological configurations where the interplay between weather variables in both space and time is determinant. Whatever the river sub-basin considered, the simulated discharges are in good agreement with the reference ones, provided that the weather scenarios are bias-corrected. The observed multi-scale variations in discharges (daily, seasonal, and interannual) are reproduced well. The low-frequency hydrological situations, such as annual monthly discharge minima (used as low-flow proxy indicators) and annual daily discharge maxima (used as flood proxy indicators), are reproduced reasonably well. The observed increase in flood activity over the last century is also reproduced rather well. The observed low-flow activity is conversely overestimated, and its variations from one sub-period to another are only partially reproduced. Bias correction is crucial for both precipitation and temperature and for both downscaling models. For the dynamical one, a bias correction is also essential for getting realistic daily temperature lapse rates. Uncorrected scenarios lead to irrelevant hydrological simulations, especially for the sub-basins at high elevation, due mainly to irrelevant snowpack dynamic simulations. The simulations also highlight the difficulty in simulating precipitation dependency on elevation over mountainous areas.

Typhoon and flooding occurrences on Chongming Island, Changjiang Estuary, as revealed by a newly acquired sedimentary record

Typhoon-induced storms surges and river flooding events represent two types of natural disasters that affect a wide range, occurring with high frequency and causing serious societal losses. Due to the limited duration of instrumental records, there is an inadequate understanding of the patterns and mechanisms underlying the variations in typhoons and floods. The interpretation of sedimentary records aptly compensates for these deficiencies in terms of the temporal scale, becoming a crucial medium for extending the temporal span of typhoon and flood records. Previous studies in this field have primarily focused on the identification of single types of extreme events. The Changjiang Estuary, particularly Chongming Island, is significantly affected by both typhoons and river floods, making it an excellent area for synchronous comparative studies of these two types of extreme events. Based on the analysis of a core sample, ZP02, collected from Chongming Island, in terms of chronological, sedimentological, and geochemical characteristics, specific tracing fingerprints for event deposits from typhoon and flood events are established. Sediments from typhoon events generally exhibit erosive contact surfaces, coarser grain sizes, and a tendency to become finer upwards, often featuring layers mixed with coarse sand and shell fragments. In contrast, flood event deposits vary in grain size, either coarser or finer, with abrupt contact surfaces compared to normal sediment layers, and are predominantly brownish-yellow in color. The fingerprint tracing results indicate that the typhoon event layers are characterized by high values in principal component 2 (PC2) of the elements, Zr/Fe and Sr/Fe ratios, with low values in principal component 1 (PC1) the elements and Ti/Ca ratio. Flood event deposits are marked by high values in PC1 and Ti/Ca ratio, low values in PC2 and Sr/Fe ratio, and an increase in Zr/Fe ratio in coarser flood layers but no significant change in finer layers. Based on these fingerprints, 19 layers of typhoon and the same number of flood events were identified in core ZP02, which correspond well with documentary records. The establishment of tracing fingerprints for typhoon and flood event deposits provides methodological support for the identification and interpretation of various extreme event deposits.

Influence of the Atlantic inflow on trace metal enrichments in sediments and particulate matter of the NW Alboran Sea (SW Mediterranean)

Trace metal contents and fluxes in downward particulate matter and dated sediment cores of the NW Alboran Sea are analysed in this study with the aim of assessing the role of the Atlantic inflow on their transport. Increases in Zn, Cu and Pb were detected in downward particulate matter collected by sediment traps after river flooding events and after the Aznalcollar mining spill. Their arrival coincided within the recently estimated time range for river particles discharged into the Gulf of Cádiz to reach the Alboran Sea, indicating that their transfer is enhanced during events of increased river inputs of contaminated particulate matter. This also suggests that the effects of potential tailing dam failures in the Gulf of Cádiz watersheds could reach the Alboran Sea. These trace metals also increased in the sediment cores from the continental rise since the second half of the 19th century, suggesting that contaminated particles have been continuously transferred towards the Mediterranean Sea since that time, when mining concessions and production increased in the SW Iberian Pyrite Belt.

Quick-Response Model for Pre- and Post-Disaster Evacuation and Aid Distribution: The Case of the Tula River Flood Event

Background: In the context of humanitarian logistics, efficiently evacuating people from disaster-stricken areas is a complex challenge. This study focuses on the Tula River region in Hidalgo, Mexico, exploring the evacuation and support of individuals in temporary shelters. Despite the fact that the topic has been addressed in the literature, it is necessary to have quick response methods that can be used by decision-makers to adapt and utilize existing spaces as temporary shelters, in addition to knowing how to evacuate people. Methods: Addressing this void, a methodology to minimize evacuation and aid distribution costs is introduced. Leveraging existing algorithms, particularly Integer Linear Programming, the model determines shelter activation and utilizes the Vehicle Routing Problem to assess aid delivery strategies. Results: The research identifies optimal evacuation routes from 13 affected areas to 34 shelters and analyzes aid distribution costs under various demand scenarios: original, increased, and decreased by 10%, based on the number of transport units allocated and Google Maps distances. It also evaluates the costs associated with humanitarian aid distribution under varying collection strategies, involving state and municipal governments. Conclusion: This approach provides a decision-making foundation and can be adapted for similar analyses in other communities during extreme events.

Risk analysis of debris and non-debris flow in the Cisokan river flood event

Cisokan River is one of the main inflow rivers of Cirata Reservoir aside from Citarum River. Cisokan River is the second largest contributor to Cirata inflow after Citarum River. In May of 2023 Cisokan River experienced instances of flash flood disasters that submerged houses in Cianjur Regency, one of the affected villages is Ciranjang Village. Several news outlets reported that this flood also left debris and mud in the affected areas, which indicated that the flood was debris flow. This study conducts the risk analysis resulting from debris and non-debris flow with the changes in river cross-section due to sedimentation. In this study, modeling was carried out employing a Digital Elevation Model (DEM) map and utilizing the Hec-RAS software. One focus of the modeling was on simulating the Newtonian (non-debris) and non-Newtonian (debris), comparing the results and analyzing the risk from both. The result showed that the non-Newtonian flow’s flood inundated area is larger than the Newtonian flow’s, which means the high flood risk area of debris flow is 12.5% larger than the non-debris flow’s high flood risk area.

Design of water level detection monitoring system using fusion sensor based on Internet of Things (IoT)

River flooding is a condition when the water in a river overflows and exceeds its normal capacity, thereby flooding the surrounding area. This flood disaster has been a known problem for a long time and causes great damage in the affected areas. Flood events inRivers are influenced by many factors, such as climate change, rapid urbanization, inappropriate land use, ineffective water management patterns, as well as uncontrolled addition of hard soil surfaces. Flood conditions in rivers involve complex processes and are influenced by various factors components, such as rainfall, water flow, topography, vegetation, and many other factors. Therefore, this research is very urgent because it can help reduce the negative impacts of flooding, increase public safety, become a basis for decision making, save costs and resources and make a positive contribution to technological development. This study aims to create a prototype of a flood early warning system. The system is based on a wireless sensor network whose interconnections are connected by a star topology. Every node is a combination of several sensors (sensor fusion) that are related to detecting floods, such as: height sensors, water flow speed sensors and rainfall intensity sensors. Design of hardware (hardware) and software (software) will be done. A classification mechanism based on Fuzzy Logic will be used to estimate flood conditions based on existing data. Flood estimation will determine the time and distance of flood events that will occur. Several experiments in the laboratory will be carried out to determine the performance of the designed system.

Challenges in the attribution of river flood events

AbstractAdvances in the field of extreme event attribution allow to estimate how anthropogenic global warming affects the odds of individual climate disasters, such as river floods. Extreme event attribution typically uses precipitation as proxy for flooding. However, hydrological processes and antecedent conditions make the relation between precipitation and floods highly nonlinear. In addition, hydrology acknowledges that changes in floods can be strongly driven by changes in land‐cover and by other human interventions in the hydrological system, such as irrigation and construction of dams. These drivers can either amplify, dampen or outweigh the effect of climate change on local flood occurrence. Neglecting these processes and drivers can lead to incorrect flood attribution. Including flooding explicitly, that is, using data and models of hydrology and hydrodynamics that can represent the relevant hydrological processes, will lead to more robust event attribution, and will account for the role of other drivers beyond climate change. Existing attempts are incomplete. We argue that the existing probabilistic framework for extreme event attribution can be extended to explicitly include floods for near‐natural cases, where flood occurrence was unlikely to be influenced by land‐cover change and human hydrological interventions. However, for the many cases where this assumption is not valid, a multi‐driver framework for conditional event attribution needs to be established. Explicit flood attribution will have to grapple with uncertainties from lack of observations and compounding from the many processes involved. Further, it requires collaboration between climatologists and hydrologists, and promises to better address the needs of flood risk management.This article is categorized under: Paleoclimates and Current Trends > Modern Climate Change Paleoclimates and Current Trends > Detection and Attribution Assessing Impacts of Climate Change > Observed Impacts of Climate Change

Backwater Effects in Rivers and Lakes: Case Study of Dongping Lake in China

In the context of global climate change, the frequency of watershed flooding events resulting from extreme rainfall has significantly increased. Especially at river or lake confluences, the presence of backwater effects greatly amplifies the flood risk. To investigate the influence of backwater effects on the hydraulic characteristics of rivers and lakes, this study focuses on the Dongping Lake in China. An enhanced two-dimensional hydrodynamic model was employed to simulate and analyze three different degrees of backwater effects. The results indicate that, compared to the working conditions without the backwater effect, the highest lake water level increased by 1.0 m and 0.1 m under severe and moderate backwater effect conditions, respectively. The total outflow flood volume decreased by 30.1% and 2.3%, respectively. The demolition time for the Jinshan Dam needs to be advanced by 12.5 h and 10.0 h, respectively, and the inundation area in the western region expanded by 2.73% and 0.32%. Additionally, the average inundation depth increased by 0.93 m and 0.08 m, respectively. These results provide valuable data support for the safe operation of Dongping Lake, the formulation of flood defense strategies, and, likewise, offer valuable insights into the risk management of flood events in other rivers and lakes with backwater effects.

2021 UK floods: event summaries and reflections from the Flood Forecasting Centre

Abstract Flooding in 2021 has highlighted the increased risk to national resilience. This is against a backdrop of the UK climate projected to become more extreme over the next few decades. This paper considers the notable river and surface water flood events within England and Wales during 2021 and examines the performance of the Flood Forecasting Centre in highlighting the flood risk to our customers. We reflect on team debriefs as well as feedback and surveys from our customers. We distil our learnings and make connections with improvements in our underpinning science, forecasting tools, products and services. Finally, we highlight challenges associated with surface water flooding and suggest how we may collectively start to overcome these.

Participatory development of storymaps to visualize the spatiotemporal dynamics and impacts of extreme flood events for disaster preparedness

Floods are one of the costliest natural hazards in Switzerland and worldwide. Therefore, society is confronted with questions about protecting people and assets from flood risks. Key instruments are protective measures, land use regulations, spatial planning, and the interventions by civil protection units if flood magnitudes exceed the protection standards. Both prevention and preparedness require risk awareness from professionals, politicians, and the public. Risk awareness is generally high after an event and low after a period without major events. However, the rarity of extreme flood events limits learning from flood events. The training of intervention forces who should manage flood events with magnitudes beyond hitherto observed flood events requires a comprehensive description and visualization of the flood processes and their impacts. To address this, together with stakeholders and civil protection and intervention planning experts, we co-developed a new way to visualize the spatiotemporal dynamics of extreme flood events and thereby communicate their impacts using dynamical flood storymaps. We selected physically plausible precipitation scenarios from reforecasts to develop storylines of extreme river flood events and their socioeconomic impacts in Switzerland. The co-development process revealed which information is relevant to potential users and how it must be presented. It is shown that storylines of extreme events presented as storymaps are a valuable tool to communicate scientific results in a way that allows practitioners to gain relevant information for their work. Therefore, we built an interactive online tool (www.flooddynamics.ch), enabling the user to analyze the spatiotemporal unfolding of flood events in Switzerland from the start of precipitation to the recession of the flood. The visualization includes maps of inundated areas at hourly timesteps and the related impacts in terms of affected persons, buildings, roads, and infrastructure. Such a temporally explicit (dynamic) representation of extreme events in storymaps, in contrast to static hazard maps, which are commonly used today, is favorable for emergency intervention planning and training and thus for awareness creation and better disaster preparedness.

Fluvial Delivery and Wave Resuspension of Sediment in a Sheltered, Urbanized Pacific Northwest Estuary

The sequence and timing of sediment delivery and redistribution in coastal systems is important for shoreline stability, ecosystem services, and remediation planning. In temperate estuaries, understanding the role of fluvial sediment delivery and dispersal relative to wind and wave remobilization processes is particularly important to address the fate of contaminants, many of which adsorb to fine particles, and to assess changes in coastal systems under projected changes in climate. Here we present an integrated analysis of observations at multiple timescales to evaluate sediment dynamics and the sedimentary coupling between fluvial and oceanographic processes within Bellingham Bay, Washington, USA, an urban estuary. Time-series data of currents, waves, and turbidity at four moorings along with geochemical data from grab samples and cores of seabed sediment from across the bay are contrasted with the dynamics of the Nooksack River, its fluvial sediment source. Even during large (5-yr return interval) river-flood events, water-column suspended-sediment concentration (SSC) near the bed on the outer delta topset was not correlated with Nooksack River runoff and was instead closely correlated with local wind-wave height. In contrast, near-surface SSC was strongly correlated with fluvial discharge, suggesting intense water-column suspended-sediment stratification during flood events. Grain-size and geochemical (7\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{7}$$\\end{document}Be and excess 210\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{210}$$\\end{document}Pb) results from seabed-sediment samples and historical bathymetric measurements of the subaqueous Nooksack River delta reveal spatial gradients of fluvial and wave influence and sediment-accumulation rates. Analysis of historical bathymetric surveys of the Nooksack River delta combined with the geochemical data reveal that about 75% of the fluvial sediment load can be accounted for in the Bellingham Bay receiving system. Studies of this type in urbanized coastal settings can help address ecological and geological questions regarding the risks from contaminants associated with fine-grained sediment, predict longer-term delta morphological evolution, and inform managers planning future coastal restoration efforts

Comparative Grain Size Analysis of Modern Flood Sediments Based on Graphic and Moment Methods in the Lower Yellow River (Huang He), China

Grain size analysis of flood sediments is a key method for understanding the sedimentary environments of rivers worldwide; however, there is limited knowledge of how to effectively reflect the sedimentary environment of lower Yellow River (Huang He) flood events using grain size parameters. In this study, two widely used grain size analysis methods, the graphic method (GM) and moment method (MM), were compared, and their applicability to flood sediment analysis in the lower Yellow River was evaluated. Modern flood sediments (n = 143) in the lower Yellow River featured a fine-grained texture and were classified as silty sand (4.95 ≤ Φ ≤ 5.03) characterized by an inadequate sorting ability. The grain size distribution patterns obtained using the GM and MM revealed positive and extremely positive deviations with sharp and flat peaks, respectively. A strong correlation (0.6966 ≤ R2 ≤ 0.9961) was observed between the mean grain size and the sorting coefficient obtained using the GM and MM. Thus, both methods were deemed suitable and could be used interchangeably. Our results indicate that the MM should be applied to assess skewness because it provided comprehensive information regarding flood sediments in the lower Yellow River, whereas the GM is recommended for kurtosis analysis, as it highlighted the primary sedimentary dynamics during flood events. Methods must be selected based on the sedimentary environment when analyzing grain size parameters.

Understanding Drivers of Salinity and Temperature Dynamics in Barataria Estuary, Louisiana

AbstractBarataria Estuary is an economically and ecologically important estuary in coastal Louisiana, USA. Due to rapid wetland loss, extreme Mississippi River flood and drought events (e.g., the flood of 2019 and the drought of 2022), devastating storm events (e.g., Hurricane Ida in 2021), eustatic sea‐level rise (SLR), high subsidence rates, and human activities, temporal and spatial variability of salinity and temperature in the estuary is highly complex. This study comprehensively investigates environmental drivers that govern salinity and temperature dynamics, as well as the effects of a proposed large‐scale, land‐building diversion of Mississippi River water. A three‐dimensional (3D), process‐based hydrodynamic, salinity and temperature transport model system is formulated and implemented. Three different modeling domains are set up for nested computations. The model system is validated for the year 2018 against measurements of water level, salinity, and temperature. A series of numerical experiments are then carried out to quantitatively examine impacts of various environmental drivers, as well as nearshore density stratification and local baroclinic forcing. The drivers include wind, rainfall, freshwater point‐source diversion, SLR, and Mississippi River discharge. Interestingly, the analysis shows that the proposed Mid‐Barataria diversion and rainfall can cause a reduction of annual salinity up to 14 and 10 ppt, respectively. Neglecting the effect of nearshore density stratification could underestimate salinity by up to 9 ppt. The well‐mixed estuary can be adequately modeled using depth‐averaged models. However, to adequately capture proper salinity and temperature stratification, it is necessary to use 3D models for the coastal regional domain.

Hotspots of microplastic accumulation at the land-sea transition and their spatial heterogeneity: The Po River prodelta (Adriatic Sea)

Deltas are the locus of river-borne sediment accumulation, however, their role in sequestering plastic pollutants is still overlooked. By combining geomorphological, sedimentological, and geochemical analyses, which include time-lapse multibeam bathymetry, sediment provenance, and μFT-IR analyses, we investigate the fate of plastic particles after a river flood event providing an unprecedented documentation of the spatial distribution of sediment as well as of microplastics (MPs), including particles fibers, and phthalates (PAEs) abundances in the subaqueous delta. Overall sediments are characterized by an average of 139.7 ± 80 MPs/kg d.w., but display spatial heterogeneity of sediment and MPs accumulation: MPs are absent within the active sandy delta lobe, reflecting dilution by clastic sediment (ca. 1.3 Mm3) and sediment bypass. The highest MP concentration (625 MPs/kg d.w.) occurs in the distal reaches of the active lobe where flow energy dissipates. In addition to MPs, cellulosic fibers are relevant (of up to 3800 fibers/kg d.w.) in all the analyzed sediment samples, and dominate (94 %) with respect to synthetic polymers.Statistically significant differences in the relative concentration of fiber fragments ≤0.5 mm in size were highlighted between the active delta lobe and the migrating bedforms in the prodelta. Fibers were found to slightly follow a power law size distribution coherent with a one-dimensional fragmentation model and thus indicating the absence of a size dependent selection mechanism during burial. Multivariate statistical analysis suggests traveling distance and bottom-transport regime as the most relevant factors controlling particle distribution. Our findings suggest that subaqueous prodelta should be considered hot spots for the accumulation of MPs and associated pollutants, albeit the strong lateral heterogeneity in their abundances reflects changes in the relative influence of fluvial and marine processes.

Dissolved organic carbon dynamics and fluxes in Mississippi-Atchafalaya deltaic system impacted by an extreme flood event and hurricanes: a multi-satellite approach using Sentinel-2/3 and Landsat-8/9 data

Transport of riverine and wetland-derived dissolved organic carbon (DOC) spanning tidal wetlands, estuaries, and continental shelf waters functionally connects terrestrial and aquatic carbon reservoirs, yet the magnitude and ecological significance of this variable and its spatiotemporal linkage remains uncertain for coastal deltaic regions, such as Mississippi River Delta Plain, which includes Mississippi (MR) and Atchafalaya (AR) rivers and estuaries with vast expanses of wetlands and coastal forests. We examined DOC dynamics and fluxes in this large river-dominated wetland-estuarine system for the period between 2019 and 2021 that included an extreme river flood event in 2019, two major hurricanes (Barry in 2019 and Ida in 2021), and cold front passage using an improved adaptive quasi-analytical algorithm (QAA-AD) applied to multi-satellite sensors (Sentinel 3A/B OLCI, Landsat-8/OLI and Sentinel-2A/B MSI) with varying spectral and spatial (10/30/300 m) resolutions. The DOC estimates from multi-satellite sensors in combination with water fluxes were used to assess DOC fluxes from two large rivers (MR and AR) and small channels across the delta plain. Overall, this system delivered a total of 6.7 Tg C yr-1(1 Tg = 1012g) into the estuarine zone and the northern Gulf of Mexico (nGoM) during 2019. High DOC fluxes from the AR (1.3 Tg C yr-1) and MR (4.5 Tg C yr-1) were associated with the extreme flood event in 2019. Hurricanes that occurred in the study period also contributed to the wetland and estuarine DOC fluxes into continental shelf waters; for example, the passage of Hurricane Barry in July 2019, delivered over a 3-day period ~1.33 ×109g DOC from Barataria Basin into the nGoM. Sentinel 2-MSI land and water classification revealed that Hurricane Ida eroded a total of 1.34×108m2of marshes in middle Barataria Basin, converting those habitats into open water with 3.0 m inundation depth and high DOC concentrations (16.4 mg L-1), a potentially large DOC source to the coastal waters. Overall, storms and flood events are major sources of DOC flux that facilitate transport of upstream carbon as well as transformation of carbon in the wetlands, through the conversion of vegetated wetland to open water.

Exploring the links between flood events and the COVID-19 infection cases in Romania in the new multi-hazard-prone era.

The occurrence of flood events amid the COVID-19 pandemic represents a prominent part of the emerging multi-hazard landscape, as floods are one of the most frequent and destructive natural hazards. This spatial and temporal overlap of hydrological and epidemiological hazards translates into compounded negative effects, causing a shift in the hazard management paradigm, in which hazard interaction takes centre stage. This paper calls into question whether the river flood events that occurred during the COVID-19 pandemic in Romania and the way that they were managed had an impact on the infection with the SARS-CoV-2 virus at county scale. To this end, hazard management data concerning the flood events that were severe enough to impose the evacuation of the population were corroborated with COVID-19 confirmed cases data. A definite link between the flood events and the dynamics of COVID-19 cases registered in the selected counties is difficult to identify, but the analysis shows that all flood events were followed by various size increases in the COVID-19 confirmed cases at the end of the incubation time range. The findings are critically interpreted by providing viral load and social-related contexts, allowing a proper understanding of the interactions between concurrent hazards.

Human disturbances dominated the unprecedentedly high frequency of Yellow River flood over the last millennium.

A warming climate may increase flood hazard through boosting the global hydrological cycle. However, human impact through modifications to the river and its catchment is not well quantified. Here, we show a 12,000-year-long record of Yellow River flood events by synthesizing sedimentary and documentary data of levee overtops and breaches. Our result reveals that flood events in the Yellow River basin became almost an order of magnitude more frequent during the last millennium than the middle Holocene and 81±6% of the increased flood frequency can be ascribed to anthropogenic disturbances. Our findings not only shed light on the long-term dynamics of flood hazards in this world's most sediment-laden river but also inform policy of sustainable management of large rivers under anthropogenic stress elsewhere.