Search Results (89)

Poyang Lake, a large floodplain lake, plays a crucial role in the ecological safety and quality of life in surrounding areas. Over the past decade (2013–2022), amid economic development and environmental changes, the water environment of Poyang Lake has encountered complex challenges. This study evaluated the water quality of Poyang Lake in a recent 10-year span by the water quality index (WQI), trophic level index (TLI) and a newly constructed comprehensive evaluation index, and it analyzed the trend of water quality change under extreme events. Meanwhile, the main factors affecting the water quality of Poyang Lake were analyzed by partial least squares (PLS), a multivariate statistical method that accounts for multicollinearity. The results indicate that: (1) The water quality of Poyang Lake in summer and autumn is slightly worse than that in spring and winter. Each water quality index reflects the distinct states of the water environment in Poyang Lake. (2) Each water quality evaluation index responds differently to influencing factors. (3) Extreme flood and drought events have markedly different impacts on the water environment of Poyang Lake, exhibiting significant spatial heterogeneity. Domestic sewage discharge and total water resources have a relatively great impact on the water environment of Poyang Lake. The results of this study provide important insights for water quality management and policy formulation in Poyang Lake, supporting sustainable regional development. Full article

Effective flood management requires a comprehensive understanding of interactions between multiple flooding sources. This study investigates compound flooding in the Brisbane River Estuary (BRE), Australia, using the MIKE 21 hydrodynamic model to assess the combined effects of tidal and riverine processes on flood extent and water levels. Unlike conventional studies that evaluate these factors separately, this research quantifies the impact of boundary condition variations at the Moreton Bay entrance on flood modelling accuracy. The model was calibrated by adjusting Manning’s n, achieving a Nash–Sutcliffe efficiency (E_ns) ranging from 0.84 to 0.95. Validation results show a 90% agreement between the simulated and observed 2011 flood extent. The findings highlight the critical role of tidal boundary conditions, as their exclusion led to a 0.62 m and 0.12 m reduction in flood levels at Jindalee and Brisbane City gauges, respectively. This study provides valuable insights for improving flood risk assessment, model accuracy, and decision-making in estuarine flood management. Full article

The Pantanal, considered the world’s largest floodplain, exhibits hydrological and ecological dynamics that are intrinsically linked to water inflows from the surrounding highlands. While the impacts of large-scale climatic phenomena and land-use changes on hydrological variables within the Upper Paraguay River Basin (UPRB) are acknowledged, their combined effects remain unknown. Recent reductions in precipitation and river discharge have adversely affected both environmental and socioeconomic aspects of the Cerrado (Brazilian Savannah) and Pantanal biomes in Brazil, raising concerns about the long-term sustainability of these important ecosystems. This study analyzes a 37-year hydrological time series (1986–2023) of rainfall, streamflow, and flooded area in three contributing basins of the Pantanal (Jauru—JB; Taquari—TB; and Miranda—MB), and reveals distinct hydrological trends influenced by different climate systems. Significant decreasing trends in rainfall and streamflow were observed in the northern JB and TB, contrasted by increasing trends in the southern MB. Consequently, a declining trend in downstream flooded areas within the Pantanal floodplain was identified. Long-term memory processes (Hurst phenomena) were identified in the time series of the Pantanal flooded area and also in the Paraguay river stage data. These findings indicate a persistent and aggregated reduction in the Pantanal’s hydrologic variables, adversely affecting its water-dependent ecology and economic activities, such as ranching, fishing, and navigation. This study underscores the necessity of adaptative management strategies to tackle the impacts of water surface loss, increased fire risks, and climate variability in the UPRB. Full article

Riparian vegetation reduces the conveyance capacity and increases the likelihood of floods. Studies that consider vegetation in flow modeling rely on unmanned aerial vehicle (UAV) data, which restrict the covered area. In contrast, this study explores advances in remote sensing and machine learning techniques to obtain vegetation data for an entire river by relying solely on satellite data, superior to UAVs in terms of spatial coverage, temporal frequency, and cost effectiveness. This study proposes a machine learning method to obtain key vegetation parameters at a resolution of 10 m. The goal was to evaluate the applicability of remotely sensed vegetation data using the proposed method on a dynamic roughness distributed runoff model in the Abukuma River to assess the effect of vegetation on the typhoon Hagibis flood (12 October 2019). Two machine learning models were trained to obtain vegetation height and density using different satellite sources, and the parameters were mapped in the river floodplains with 10 m resolution based on Sentinel-2 imagery. The vegetation parameters were successfully estimated, with the vegetation height overestimated in the urban areas, particularly in the downstream part of the river, then integrated into a dynamic roughness calculation routine and patched into the RRI model. The simulations with and without vegetation were also compared. The machine learning models for density and height obtained fair results, with an R² of 0.62 and 0.55, respectively, and a slight overestimation of height. The results showed a considerable increase in water depth (up to 17.7% at the Fushiguro station) and a decrease in discharge (28.1% at the Tateyama station) when vegetation was considered. Full article

Iraq faces significant challenges in sustainable water resource management, due to intensive agriculture and climate change. Modern irrigation leads to depleted natural springs and abandoned traditional canal systems, creating a nexus between climate, water availability, agriculture, and cultural heritage. This work unveils this nexus holistically, from the regional to the local scale, and by considering all the components of the nexus. This is achieved by combining five decades (1974–2024) of satellite data—including declassified HEXAGON KH-9, Copernicus Sentinel-1/2/3, COSMO-SkyMed radar, and PlanetScope’s Dove optical imagery—and on-the-ground observations (photographic and drone surveying). The observed landscape changes are categorised as “proxies” to infer the presence of the given land processes that they correlate to. The whole of southern Iraq is afflicted by dust storms and intense evapotranspiration; new areas are desertifying and thus becoming local sources of dust in the southwest of the Euphrates floodplain and close to the boundary with the western desert. The most severe transformations happened around springs between Najaf Sea and Hammar Lake, where centre-pivot and herringbone irrigation systems fed by pumped groundwater have densified. While several instances of run-off and discharge highlight the loss of water in the western side of the study area, ~5 km² wide clusters of crops in the eastern side suffer from water scarcity and are abandoned. Here, new industrial activities and modern infrastructure have already damaged tens of archaeological sites. Future monitoring based on the identified proxies could help to assess improvements or deterioration, in light of mitigation measures. Full article

As the largest inland river in China, the Tarim River’s flood events significantly influence its riverbed formation. This paper took the Alar to Xinquman section of the Tarim River as the study area. The study area’s digital elevation model of the river was constructed using historical Google images and Copernicus DEM 30. Six different flood events were selected, corresponding to flood events with varying sediment loads, flood volumes, and peak flow volumes. The MIKE 21 software was used to simulate and investigate the response of the riverbed shape to different flood events. The experimental findings indicate that the sand content constitutes a pivotal factor in the formation of the riverbed during flood events. Flood sediment load goes through stages linked to changes in riverbed erosion and deposition. The combination of high peak flow and bed-forming flow after the peak effectively shapes the central channel’s morphology. The fourth type of flood event had the highest sediment transport coefficient Φ among the six types of floods and caused the most significant scouring effect on the riverbed under low sediment load conditions. Full article

The concept of Landscape Sensitivity is now more topical than ever, given the intense stresses associated with increasing hydrogeological instability because of strong anthropic pressures and extreme climatic events. One of the environments most affected by anthropogenic stresses and catastrophic weather events is undoubtedly the river environment. Studies conducted in the river plains of the Marche region in Italy, starting from the second half of the last century till today, have shown that the deepening of the riverbed is of a maximum of 10 m in the main river channels. Subsequently, these incisions were amplified by the massive impermeabilization of the floodplains and by works in the riverbeds, built to prevent erosion. In the basins of Chienti and Potenza Rivers, the downcutting was about 4–8 m, compatible with the averages of the Marche region rivers for the same period. These deepenings were subsequently amplified, starting in the mid-1980s, with the construction of sewage treatment plants near the main watercourses. In many cases, erosion phenomena, both lateral and vertical, have been observed, sometimes triggering landslide movements in the proximal banks. The analyses made it possible to highlight that this imbalance in river dynamics is due to the convergence of physical processes, such as the increase in discharge, and chemical processes that produce alteration of clay minerals related to surfactants and other chemical pollutants. This study represents a first attempt to highlight a little-known issue that could influence river sustainability of areas subject to significant anthropic pressures. Full article

Knowledge of river bathymetry is crucial for accurately simulating river flows and floodplain inundation. However, field data are scarce, and the depth and shape of the river channels cannot be systematically observed via remote sensing. Therefore, an efficient methodology is necessary to define effective river bathymetry. This research reconstructs the bathymetry from existing global digital elevation models (DEMs) and water surface elevation observations with minimum human intervention. The methodology can be considered a 1D geometric inverse problem, and it can potentially be used in gauged or ungauged basins worldwide. Nine global DEMs and two sources of water surface elevation (in situ and remotely sensed) were analyzed across two study areas. Results highlighted the importance of preprocessing cross-sections to align with water surface elevations, significantly improving discharge estimates. Among the techniques tested, one that combines the slope-break concept with the principles of mass conservation consistently provided robust discharge estimates for the different DEMs, achieving good performance in both study areas. Copernicus and FABDEM emerged as the most reliable DEMs for accurately representing river geometry. Overall, the proposed methodology offers a scalable and efficient solution for cross-section reconstruction, supporting global hydraulic modeling in data-scarce regions. Full article

Despite significant advancements in flood forecasting using machine learning (ML) algorithms, recent events have revealed hydrological behaviors deviating from historical model development trends. The record-breaking 2019 flood in the Ottawa River basin, which exceeded the 100-year flood threshold, underscores the escalating impact of climate change on hydrological extremes. These unprecedented events highlight the limitations of traditional ML models, which rely heavily on historical data and often struggle to predict extreme floods that lack representation in past records. This calls for integrating more comprehensive datasets and innovative approaches to enhance model robustness and adaptability to changing climatic conditions. This study introduces the Next-Gen Group Method of Data Handling (Next-Gen GMDH), an innovative ML model leveraging second- and third-order polynomials to address the limitations of traditional ML models in predicting extreme flood events. Using HEC-RAS simulations, a synthetic dataset of river flow discharges was created, covering a wide range of potential future floods with return periods of up to 10,000 years, to enhance the accuracy and generalization of flood predictions under evolving climatic conditions. The Next-Gen GMDH addresses the complexity and limitations of standard GMDH by incorporating non-adjacent connections and optimizing intermediate layers, significantly reducing computational overhead while enhancing performance. The Gen GMDH demonstrated improved stability and tighter clustering of predictions, particularly for extreme flood scenarios. Testing results revealed exceptional predictive accuracy, with Mean Absolute Percentage Error (MAPE) values of 4.72% for channel width, 1.80% for channel depth, and 0.06% for water surface elevation. These results vastly outperformed the standard GMDH, which yielded MAPE values of 25.00%, 8.30%, and 0.11%, respectively. Additionally, computational complexity was reduced by approximately 40%, with a 33.88% decrease in the Akaike Information Criterion (AIC) for channel width and an impressive 581.82% improvement for channel depth. This methodology integrates hydrodynamic modeling with advanced ML, providing a robust framework for accurate flood prediction and adaptive floodplain management in a changing climate. Full article

This study focuses on the analysis of sediment core retrieved from the deepest part (25 m) of Pirovac Bay. A long sedimentary sequence (7.45 m) supplemented by a shorter sediment core (1.45 m) from a shallower part of the bay was analyzed for sedimentological, mineralogical, geochemical, and micropaleontological (ostracod) parameters. The sediment thickness above the underlying karst paleorelief (karstic bedrock) is up to 12 m. Sediments recorded a transition from a freshwater to a marine environment starting from post-Neapolitan Yellow Tuff tephra sedimentation. First, the floodplain developed in Pirovac Bay, with intermittent pools and ponds, followed by wetland environment. The formation of a shallow freshwater paleolake during the Middle Holocene at 10 cal kyr BP was enabled by the rising sea level and high freshwater input from the karstified underground from the adjacent Lake Vrana (Biograd na Moru). The onset of marine intrusions through the karstified underground is evident with formation of a brackish lake in the Pirovac Bay basin. Marine transgression and flooding of the bay occurred at 7.3 cal kyr BP, evidenced by the geochemical and ostracod parameters, providing crucial insights into the dynamics of coastal inundation under past climate change. Intriguingly, freshwater ostracod species were still present in the marine sediments, brought into the bay from Lake Vrana through surficial canal Prosika and groundwater discharge (numerous estavelles) along the northeastern shores of the bay, proving their mutual influence. This submerged Holocene freshwater paleolake, reported here for the first time, underlines the sensitivity of coastal karst systems to the rise in sea level and serves to stress how important understanding of these processes is for effective management in coastal zone and climate change adaptation strategies. The findings provided evidence supporting the existence of coastal marine basins as freshwater lakes prior to being flooded by seawater as a consequence of the Holocene post-glacial sea level rise. Full article

Seasonal changes, sea level rise, and global warming make flood events more frequent, which necessitates watershed management and efficient use of water resources. In this context, understanding the hydrodynamic behavior of basins is critical for the development of flood prevention strategies. The contributions of hydrological and hydraulic modeling techniques in this process are among the key determinants of sustainable water resources management. The Filyos Sub-Basin, located in the Western Black Sea Basin, stands out as one of the regions where flood risk assessment is a priority, as it has two important floodplains. This study aims to analyze the flood risk in the Filyos River Sub-Basin with hydraulic modeling methods, and to determine the Manning roughness coefficient. In the study, the parameters affecting the roughness of the river bed were analyzed using the Cowan method, and the effects of vegetation on river bed resistance were evaluated in the laboratory environment. Flood simulations were carried out for four different flow rates (Q₁₀₀₀, Q₅₀₀, Q₁₀₀ and Q₅₀) using the HEC-RAS model, and the performance of flood protection structures were analyzed. The findings show that a significant portion of the existing protection structures are unable to meet the potential flood flows, which can cause serious damage to residential and agricultural areas. In basins with limited historical discharge data, such as the Filyos River, these findings provide important contributions to sustainable water resources management and regional planning processes. The results of the study serve as a reference for flood risk assessment, not only for the Filyos River Basin, but also for other basins with similar hydrodynamic characteristics. It is envisaged that future research, supported by larger data sets, can improve the accuracy of flood simulations. Furthermore, the Cowan method and HEC-RAS model used in this study are expected to contribute to strategic planning and engineering solutions to minimize flood risk in other watershed management projects. In future studies, we plan to further develop methodological approaches for determining the roughness coefficient, and to address applications to increase the effectiveness of flood protection structures. Full article

This study addresses the limitations of and the common challenges faced by one-dimensional river-routing methods in hydrological models, including the National Water Model (NWM), in accurately representing coastal regions. We developed a two-way coupling between the NWM and the Semi-implicit Cross-scale Hydroscience Integrated System Model (SCHISM). The approach demonstrated improvements in modeling coastal river dynamics, particularly during extreme events like Hurricane Matthew. The coupled model successfully captured tidal influences, storm surge effects, and complex river–river interactions that the standalone NWM missed. The approach revealed more accurate representations of peak discharge timing and magnitude as well as water storage and release in coastal floodplains. However, we also identified challenges in reconciling variable representations between hydrological and hydraulic models. This work not only enhances the understanding of coastal–riverine interactions but also provides valuable insights for the development of next-generation hydrological models. The improved modeling capabilities have implications for flood forecasting, coastal management, and climate change adaptation in vulnerable coastal areas. Full article

The Arabian Desert is characterised by very low rainfall and high evaporation, yet over 210 springs are on its northeastern edge in central Iraq along the Abu Jir lineament, which represents the western depositional margin of a foreland basin infilled by the floodplain sediments of the Tigris and Euphrates Rivers; there is little evidence of faulting. The springs discharge from gently east-dipping Paleocene–Eocene limestones, either where groundwater flowpaths intersect the ground surface or where groundwater flow is forced to the surface by confining aquitards. Calculated annual recharge to the aquifer system across the Arabian Desert plateau (130–500 million m³) is significant, largely due to rapid infiltration through karst dolines, such that karst porosity is the primary enabler of groundwater recharge. The recharge is enough to maintain flow at the Abu Jir springs, but active management of groundwater extraction for agriculture is required for their long-term sustainability. The hydrochemistry of the springs is determined by evaporation, rainfall composition (high SO₄ concentrations are due to the dissolution of wind-blown gypsum in rainfall), and plant uptake of Ca and K (despite the sparse vegetation). Limestone dissolution has relatively little impact; many of the springs are undersaturated with respect to calcite and lack tufa/travertine deposits. The springs at Hit-Kubaysa contain tar and high levels of H₂S that probably seeped upwards along subvertical faults from underlying oil reservoirs; this is the only location along the Abu Jir lineament where deep-seated faults penetrate to the surface. The presence of hydrocarbons reduces the Hit-Kubaysa spring water and converts the dissolved SO₄ to H₂S. Full article

China experiences frequent heavy rainfall and flooding events, which have particularly increased in recent years. As flood storage zones (FDZs) play an important role in reducing disaster losses, their ecological restoration has been receiving widespread attention. Hongze Lake is an important flood discharge area in the Huaihe River Basin of China. Previous studies have preliminarily analyzed the protection of vegetation zones in the FDZ of this lake, but the future growth trend of typical vegetation in the area has not been considered as a basis for the precise protection of vegetation diversity and introductory cultivation of suitable species in the area. Taking the FDZ of Hongze Lake as an example, this study investigated the change trend of the suitability of typical vegetation species in the Hongze Lake FDZ based on future climate change and the distribution pattern of the suitable areas. To this end, the distribution of potentially suitable habitats of 20 typical vegetation species in the 2040s was predicted under the SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5 climate scenarios using the latest Coupled Model Intercomparison Project CMIP6. The predicted distribution was compared with the current distribution of potentially suitable habitats. The results showed that the model integrating high-performance random forest, generalized linear model, boosted tree model, flexible discriminant analysis model, and generalized additive model had significantly higher TSS and AUC values than the individual models, and could effectively improve model accuracy. The high sensitivity of these 20 typical vegetation species to temperature and rainfall related factors reflects the climatic characteristics of the study area at the junction of subtropical monsoon climate and temperate monsoon climate. Under future climate scenarios, with reference to the current scenario of the 20 typical species, the suitability for Nelumbo nucifera Gaertn decreased, that for Iris pseudacorus L. increased in the western part of the study area but decreased in the eastern wetland and floodplain, and the suitability of the remaining 18 species increased. This study identified the trend of potential suitable habitat distribution and the shift in the suitability of various typical vegetation species in the floodplain of Hongze Lake. The findings are important for the future enhancement of vegetation habitat conservation and suitable planting in the study area, and have implications for the restoration and conservation of vegetation diversity in most typical floodplain areas. Full article

At the end of the Pleniglacial and the first half of the Late Glacial period, approximately between 18 and 14 ka BP, rivers of the central and southern parts of the East European Plain had channels up to 10 times as large as the present day channels of the same rivers. These ancient channels, called large meandering palaeochannels, are widespread in river floodplains and low terraces. The hydrological regime of these large rivers is of great interest in terms of the palaeoclimatology of the late Marine Isotope Stage 2 (MIS 2). In this study, we aimed at quantitative estimation of maximum flood discharges of rivers in the Dnepr, Don and Volga basins in the late MIS 2. To approach this, we used massive measurements of the morphometric characteristics of large palaeochannels on topographic maps and remote sensing data—palaeochannel width, meander wavelength and their relationships with river flow parameters. The runoff depth of the maximum flood, which corresponds to the maximum depth of daily snow thaw during the snowmelt period, was obtained for unit basins with an area of <1000 km². The mean value for the southern megaslope of the East European Plain was 44.2 mm/day (6 times the modern value), with 46 mm/day for the Volga River (5.5 times), 45 mm/day (6.3 times) for the Don River and 39 mm/day (8 times the modern value) for the Dnepr River basins. In general, the Dnepr basin was drier than the Don and Volga basins, which corresponds well to the modern distribution of humidity. At the same time, the westernmost part of the Dnepr River basin was relatively wet in the past, and the decrease in humidity from the past to the modern situation was greater there than in the eastern and central regions. The obtained results contradict the prevailing ideas, based mainly on climatic modeling and palynological data, that the climate of Europe was cold and dry during MIS 2. The reason is that palaeoclimatic reconstructions were made predominantly for the LGM epoch (23–20 ka BP). On the East European Plain, the interval 18–14 ka BP is rather poorly studied. Our results of paleoclimatological and palaeohydrological reconstructions showed that the Late Pleniglacial and the first half of the Late Glacial period was characterized by a dramatic increase in precipitation and river discharge relative to the present day. Full article