Floodplain Research Articles

Identifying Temporal Change in Urban Water Bodies Using OpenStreetMap and Landsat Imagery: A Study of Hangzhou City

As one of the most important ecosystems, the water body is losing water during the rapid development of the city. To understand the impacts on water body change during the rapid urbanization period, this study combines data from the OpenStreetMap platform with Landsat 5/Thematic Mapper images to effectively and accurately identify small urban water bodies. The findings indicate that the trained U-net convolutional neural network (U-Net) water body extraction model and loss function combining Focal Loss and Dice Loss adopted in this study demonstrate high precision in identifying water bodies within the main urban area of Hangzhou, with an accuracy rate of 94.3%. Trends of decrease in water areas with a continuous increase in landscape fragmentation, particularly for the plain river network, were observed from 1985 to 2010, indicating a weaker connection between water bodies resulting from rapid urbanization. Large patches of water bodies, such as natural lakes and big rivers, located at divisions at the edge of the city are susceptible to disappearing during the rapid outward expansion. However, due to the limitations and strict control of development, water bodies, referring to as wetland, slender canals, and plain river networks, in the traditional center division of the city, are preserved well. Combined with the random forest classification method and the U-Net water body extraction model, land use changes from 1985 to 2010 are calculated. Reclamation along the Qiantang River accounts for the largest conversion area between water bodies and cultivated land, constituting more than 90% of the total land use change area, followed by the conversion of water bodies into construction land, particularly in the northeast of Xixi Wetland. Notably, the conversion of various land use types within Xixi Wetland into construction land plays a significant role in the rise of the carbon footprint.

Predicting the geospatial distribution of Chinese rice nutrient element in regional scale for the geographical origin—A case study on the traceability of Japonica rice

AbstractEffective geographical origin discrimination of Chinese rice requires a large database of samples to ensure sufficient data for origin verification at a regional scale. In this study, environmental similarity was used to establish a spatial database of rice nutrient element, and then the validity of the database was verified using the back propagation artificial neural networks modeling (BPNN). The spatial distribution model of 14 rice nutrient element (Al, Ba, Ca, Cu, Cr, Fe, K, Mg, Mn, Mo, Na, Ni, Rb, and Zn) on regional scale was built using an environmental similarity method for the first time. Elemental concentrations of 692 samples were used to build a simulated geographical origin prediction model for northeastern (N‐E), middle to lower Yangtze River plain (Y‐R), southwestern (S‐W), and southeastern (S‐E) in China. The results indicated that the performance of the environmental similarity model for these four growing regions was S‐W > N‐E > S‐E > Y‐R based on the lowest ranking root mean square error (RMSE) for each region. For example, the RMSEs of Zn in S‐W, N‐E, S‐E, and Y‐R regions were 2.0, 2.4, 2.7, and 3.7 mg/kg, respectively. A case study on the traceability of Japonica rice was shown that Japonica rice could be discriminated with higher origin accuracy using a simulated database (91.8%) than by the actual database (87.0%) using the BPNN model. This indicates that a simulated rice element database could improve the accuracy of geographical origin discrimination for Chinese rice and potentially be applied to other large national‐scale crop datasets.

A Preliminary Study of Past Geological Disasters in the Trowulan Majapahit Cultural Heritage Area, Mojokerto Regency, East Java

Abstract Numerous sites found buried in the Trowulan Cultural Heritage Area makes the area suspected of being the capital of the Majapahit Kingdom (13-15th century). The condition of the buried site raises an assumption of a past catastrophic event that hit and buried part of Trowulan area, causing the downfall of the Majapahit Kingdom. This assumption is supported by the existence of several books and inscriptions from the Majapahit Kingdom period that record events interpreted as geological disasters. Although there is a lot of evidence, however, what kind of geological disaster that hit the Trowulan area is not known for certain. This study aims to identify what kind geological disasters that buried the Trowulan Capital area based on previous studies and GIS analysis. The results inferred that flash floods and volcanic eruptions contributed to the burial of Trowulan Capital Region, which is supported by the geographical conditions of the capital city of Trowulan where the northern part is a flood plain and the southern part is part of the Jatirejo alluvial fan. Stratigraphic data collection needs to be carried out in the future as supporting evidence to know the detailed sequence of disaster events and the direction of the disaster flow.

Urban flash flood prediction modelling using probabilistic and statistical approaches

The development of a detailed strategy to mitigate the negative consequences of any natural calamities depends on accurately identifying sensitive zones where natural hazards frequently happen. In the present investigations, three widely utilized probabilistic approaches viz., frequency ratio (FR), statistical index (SI), and weighting factor (WF) have been utilized for prediction of flsh flood susceptibility zones in the Coochbehar urban and peri-urban area (CUPUA) (area = 26.22 km2). Ten flash flood conditioning factors have been used in this assessment based on previous literatures and experts' opinions. In the FR model, 29.40 % area is observed in the high and very high flood zones, whereas 36.27 % and 31.16 % area is identified in SI and WF model, respectively. The FR model demonstrates that five conditioning factors, viz., topographic position index (TPI), land use and land cover (LULC), normalized difference vegetation index (NDVI), distance to drainage (DtD) and rainfall were highly impacted in flash flood prediction (FFP) analysis; in SI model, LULC is the major influencing parameter, and in WF model LULC, rainfall, NDVI, and distance to road (DtR) are the effective parameters. The success rate curve of the FR, SI and WF models manifest SI model has highest training (AUC=0.903) and prediction (AUC=0.925) accuracy, and FR and WF also have very good accuracy as their AUC values are 0.899 and 0.877 (in success rate curve) and 0.900 and 0.881 (in prediction rate curve). Therefore, the application of probabilistic approaches in this active flash flood-prone region is excellently performed, and the results of this study will help hydrologists, engineers, and water management administrators to control the areas that are extremely susceptible to flash floods and reduce possible damages.

Geophysical Investigation of Bulding Distress in Gashua, Nigeria

Gashua is the Headquarter of Bade local government in Yobe State, it has a population of about 125, 000 according to the 2006 population census. It is a densely populated town located in a flood plain within the Chad Basin. In an attempt to proffer solutions to the prevailing building distress in Gashua and its environs, this study was carried out to accurately characterize the subsurface geology of the area, thereby reducing the incidence of building failure in the area to minimum. In this study, electrical resistivity method was used to determine the causes of building distress and failure in Gashua and its environs. Vertical Electrical Sounding (VES) using Schlumberger array and Electrical Resistivity Tomography (ERT) were adopted for the study. The results of the VES survey showed that the area is composed of five geologic layers which are; the topsoil, clay, sand, sandy-clay, and sand. The ERT results showed that most of the building foundations in the study area were laid within the second layer which is a clay formation. The findings of this study showed that the building distress and failure which are common in the study area were caused by the volumetric changes of the clay formation due to hydrological dynamics. The clay formation absorbs water during the raining season and swells up, and during the dry season it shrinks, this changes in the volume of the clay formation underlying the building foundation in the study area induces a significant mechanical stress on the buildings leading to the formation of cracks, voids, fissures and fracturing of the buildings, which eventually culminate into collapse. In this study, electrical resistivity method of geophysical investigation has demonstrated to be a veritable tool for geotechnical soil evaluation. Based on the findings of this study, geophysical investigation of a proposed site...

Technogenic transformation of the Lena River floodplain near Yakutsk and assessment of landscape disturbance

The Tuymaada Valley located in the Yakutsk region represents the most developed region within the Lena River fllodplain. Landscape studies conducted here between 2016 and 2022 revealed a significant level of technogenic transformation: 30.4 % of its sites showed a high and moderate degree of disturbance. The primary driver of landscape development was the transformation of forested areas into meadows due to centuries of grazing in the floodplain. The current trend in evolution involves replacing agricultural stows with residential ones, leading to an increase in mechanical disturbances to the landscape structure. Water protection dams have removed significant areas of the left bank floodplain from the flood zone. Consequently, some of its stows become swamped, while others transform into dry wastelands with low-value steppe meadows. Currently, at the investment justification stage, the issue of providing comprehensive protection for the entire left bank of the Tuymaada valley from the adverse effects of floods and inundations is under consideration. For its continued growth, it is essential to implement not just protective measures but also environmental and improvement measures for both existing and new urban, rural, and economic-technical zones on the developing technogenic terrace.

Geospatial Analysis of Flood Susceptibility in Nigeria’s Vulnerable Coastal States: A Detailed Assessment and Mitigation Strategy Proposal

This study employs advanced geospatial analytical techniques to evaluate the vulnerability of Nigeria’s coastal states and their constituent local government areas to flood hazards, which represent a critical and escalating risk within the coastal hazard paradigm intensified by climate change phenomena. The study’s objective is to utilize geospatial data to delineate and quantify the intensity and distribution of flood susceptibility, thus establishing a foundational framework for developing comprehensive disaster management strategies in response to the challenges posed by climate variability. The research uses satellite imagery and geographic information system (GIS)-based hydrological modeling to delineate regions susceptible to flooding, synthesizing topographical and hydrological data to stratify areas into discrete flood susceptibility categories. The findings indicate that the Delta coastal State of Nigeria contains extensive medium to high-risk flood zones spanning 8304.57 km2. While the Bayelsa coastal State of Nigeria presents critical areas at high to very high flood risk, encompassing 5506.61 km2 at high risk and 1826.88 km2 at very high risk, this highlights the urgent necessity for immediate and strategic mitigation measures. This research highlights the critical importance of geospatial technology in shaping disaster management and enhancing community resilience against increasing flood frequencies. As Nigeria’s coastal regions face escalating flood susceptibility, advanced geospatial methods are vital for assessing and mitigating these climate-induced threats, contributing to climate-resilient planning and aligning with Sustainable Development Goal 13: Climate Action. The study’s geospatial approach delivers precise flood risk evaluations and guides targeted mitigation efforts, marking significant progress in managing coastal hazards in a changing climate.

Assessment of vulnerability to flood risk in the Padma River Basin using hydro-morphometric modeling and flood susceptibility mapping.

An evaluation of flood vulnerability is needed to identify flood risk locations and determine mitigation methods. This research introduces an integrated method combining hydro-morphometric modeling and flood susceptibility mapping to assess Padma River Basin's flood risk. Flood zoning, flooding classes, and resource flood risk were explicitly analyzed in this river basin study. Flood risk was calculated using GIS-based hydro-morphometric modeling. Using Horton's and Strahler's methods, drainage density, stream density, and stream order of the Padma River Basin were determined. The Padma River Basin has five sub-basins: A, B, C, D, and E, with stream densities of 0.53km-2, 0.13km-2, 0.25km-2, 0.30km-2, and 0.28km-2 and drainage densities of 0.63km-1, 0.16km-1, 0.29km-1, 0.35km-1, and 0.33km-1, respectively. Sub-basin A is the most prone to floods due to its high stream and drainage density, whereas B and C are the least susceptible. This study used elevation, TWI, slope, precipitation, NDVI, distance from road, drainage density, distance from river, LU/LC, and soil type to create a flood vulnerability map incorporating GIS and AHP with pair-wise comparison matrix (PCM). The study's flood zoning shows that the northeastern part of this basin is more likely to flood than the southwestern part due to its elevation and high-order streams. Moderate River Flooding, the region's most hazardous flood class, covers 48.19% of the flooding area, including 1078.30 km2 of agricultural land, 94.86 km2 of bare soil, 486.39 km2 of settlements, 586.42 km2 of vegetation cover, and 39.34 km2 of water bodies. The developed hydro-morphometric model, the flood susceptibility map, and the analysis of this data may be utilized to offer long-term advance alarm insight into areas potentially to be invaded by a flood catastrophe, boosting hazard mitigation and planning.

Analysis dam failure and flood inundation mapping: a case study of Manbaa-Al-Ghozlan dam, Biskra, Algeria

Floods in all their form are considered a real threat to many regions of the world. There are various types of floods, including those caused by the collapse of dams, which must be predicted to mitigate their effects. One of the non-structural solutions for flood mitigation and control is drawing the dam failure hazard map using effective and accurate flood models, which are essential for flood disaster prevention and mitigation. The study aims at the delineation of the flood plain area caused by Manbaa-Al-Ghozlan dam failure in the city of Biskra (About 40 km downstream the dam) and the surrounding communities (the village of El Outaya). Two scenarios were considered and simulated using the HEC-RAS 2D (River Analysis System) software, the first one is related to the sudden collapse of the dam and the second linked to under-evaluations of the projected flood of the dam spillway. The results of the first scenario confirmed that there are no risks threatening the city of Biskra taking into account the water depth which reached 5 meters in the city of El Outaya. Conversely, the water depth varying between 16m and 40m in the city of El Outaya and can exceed 16 meters in the city of Biskra for the second scenario, and this performs as a great danger for the zone. This simulation allowed designing the dam failure hazards map, which showed the areas threatened by flood waves, and consequently required a plan of security measures to moderate as much as possible the consequences of a dam collapse.

Drought-Stressed Apple Tree Grafted onto Different Rootstocks in a Coastal Sandy Soil: Link between Fast Chlorophyll a Fluorescence and Production Yield

Domesticated apple is a drought-sensitive species that spread from continental to Mediterranean temperate regions, where it can particularly experience prolonged water stress. One strategy to improve drought resistance in apple is engrafting on selected rootstocks. This study explores the potential of fast chlorophyll a fluorescence for the comparison of rootstock sensitivity to drought, looking for significant correlations with fruit productivity. The experiment was conducted in a field located in the coastal Po River Plain, Northern Italy, characterized by a loamy sandy soil, particularly prone to drought (86% sand). Mature plants of apple cv. Superchief® Sandidge engrafted on three different rootstocks (CIVP21pbr, MM106, M26) were monitored throughout the summer of 2021 and compared between irrigated and non-irrigated parcels, and at the end of the season, fruit production was evaluated. Despite soil water tension only reaching −13 kPa, the non-irrigated plants experienced a small but consistent loss of Photosystem II (PSII) activity and a lesser capacity of light energy conservation in the photosynthetic electron transport chain. The fruit weight correlated with PSII photochemical indexes recorded during early drought, particularly FV/FM and PIABS; a correlation emerged between fruit number per plant and median values of electron transport parameters, including PITOT. Although all rootstocks underwent a 40% loss of productivity, the fluorescence parameters revealed a graded susceptibility to drought, M26 > CIVP21pbr > MM106, which matched well with the plant vigour. The least drought-sensitive MM106 produced less numerous but heavier fruits than the other two rootstocks.

Floodplain carbon dioxide emissions strongly exceed those of the main river stem: A case study of the Ob River, western Siberia

The importance of floodplains in carbon (C) evasion from the lotic systems is especially important in continental plains of low runoff such as the organic-rich Western Siberian Lowland (WSL). To quantify the relative importance of the floodplain compared to main stem CO2 emissions, we monitored a large region of the Ob River’s middle course (permafrost-free zone) over 3 months from spring to summer. We calculated seasonal water coverage using remote sensing, GIS and hydrologically-based approaches and measured CO2 emissions using floating chambers. There was a strongly pronounced seasonality in the water area’s extent of the floodplain with water covering > 40 % of land during the ∼ 30 days of the most intensive spring flood (May – June) and subsequently declining to ≤ 10 % during summer (July-August). Maximal CO2 emissions were recorded in most shallow water bodies of the floodplain, notably in temporary flooded fens and birch forests. The CO2 emissions during the study period ranged from 0.2 ± 0.2 to 0.9 ± 0.2 g Cm−2 d-1 for the floodplain and 0.03 ± 0.34 g C m−2 d-1 for the Ob’s main channel.CO2 emissions from the floodplain were ∼ 163 ± 20 t C per km for the river’s main stem during the 95 day study period. The partial contributions of temporary flooded zones, main stem, and permanent lakes / secondary channels to total emissions (1820 km² area) were 70, 16, and 14 %, respectively. Over spring and summer seasons, contributions from flooded zones ranged from 43 to 99 % of total CO2 emissions from water surfaces of the Ob River’s middle course. Extrapolation of obtained results to the entire territory of the Ob River floodplain indicates that not accounting for the floodplain emissions may sizably—up to an order of magnitude—underestimate the CO2 emissions from riverine systems in Western Siberia during open water period. Future work on the Ob River floodplain in the permafrost-bearing zone should be prioritized and would allow adequate upscaling of C emission from this environmentally important territory.

A Pore-Scale Phase Field Model for CO2-Fluid-Basalt Interactions.

Basalt is a suitable target area for CO2 storage. Clarifying the evolution of the pore structure during CO2-fluid-basalt interactions is a crucial element in the preparation of a CO2 geologic storage operation. In this study, a pore-scale phase field model is proposed to simulate the CO2-fluid-basalt interaction process of Snake River Plain basalt. Our model is suitable for complex multimineral natural rocks, and the initial mineral distribution before the reaction can be completely based on a real 3D rock image without the need to simplify the mineral geometry. The simulation results demonstrate that after 120 days of dissolution-precipitation reaction, the volume of secondary minerals (3.75%) exceeds that of dissolved minerals (2.01%), leading to a reduction in porosity by 1.74%. The pore structure of the basalt changes significantly, and the connectivity is obviously reduced. The effects of temperature and pressure on the reaction rate were examined to guide site selection for CO2 sequestration. The results show that increasing temperature and pressure can accelerate the reaction rate, but the impact of pressure on the reaction rate is negligible compared to the significant influence of temperature. Therefore, an area with a high geothermal gradient is conducive to geological sequestration.

A novel voting ensemble model empowered by metaheuristic feature selection for accurate flash flood susceptibility mapping

This study addresses the challenges of flash flood susceptibility mapping in Yemen’s Qaa’Jahran Basin, characterized by complex terrain and limited hydro-meteorological data. To enhance predictive accuracy, we integrate metaheuristic feature selection with ensemble learning models. Initially, fifteen flash flood variables were retrieved using Geographic Information System (GIS) based remote sensing, setting the stage for a novel feature selection algorithm. Then, the Memo Search Algorithm (MSA), a metaheuristic approach is proposed to efficiently reduce feature space. Through comprehensive comparisons with established algorithms such as the Artificial Bee Colony (ABC) and Gray Wolf Optimizer (GWO), MSA refined the selection, identifying 'elevation’ and 'distance to streams’ as optimal factors. Statistical validations using the Friedman and Wilcoxon signed-rank tests confirmed the significant superiority of MSA over competing algorithms. Ensemble classifiers (bagging, boosting, stacking) were then applied to the reduced feature space. Comprehensive evaluation revealed the boosting ensemble with MSA outperformed traditional techniques reaching 98.75% accuracy, 0.9896 Area Under the Curve (AUC), and 98.95% the harmonic mean of the precision and recall (F1-score). Precision in identifying high-risk flash flood zones was underlined via spatial prediction, confirming the integrated framework’s ability to significantly improve forecast accuracy. The findings aid disaster management with powerful geographic mapping in data-poor regions. The proposed framework is adaptable globally for flash flood-prone areas with similar constraints. As climate change is expected to increase extreme rainfall events, communities globally will need robust data-driven methodologies for flash flood susceptibility mapping. The Key recommendations of the current study include investigating hybrid feature selection methods to better enhance predictive inputs and analyzing transferability across hydro-climatic zones.

HYDROLOGICAL REGIME OF THE IKVA RIVER (SOUTHERN BUG BASIN)

This article reveals the issue of a detailed study of the hydrological regime of small plain rivers in the presence of data from regular observations. The Ikva River, the object of our study, belongs to the Southern Bug basin and is its small tributary, on which a hydrological indicators monitoring station has been operating since 1939. Since 1955, a continuous series of observations has been available, which allowed us to carry out a detailed analysis and description of the main hydrological characteristics – levels (H, cm) and water flows (Q, m3/s), to evaluate their fluctuations in time, cyclicity and the relationship Q= f(H). The construction of the corresponding graphs confirmed that the Ikva River is characterized by cyclic flow fluctuations, and since 1965 we have already observed two complete cycles of fluctuations in water level lasting about 30 years. At the moment (2022), the flow indicators record the minimum of the low-water phase of the second cycle, so we can expect an increase in the flow in the near future and the transition to a new cycle. We have also determined that the amplitude of water level fluctuations of the Ikva River at the post in the village of Stara Sinyava over many years is 60 cm, and varies from a minimum of 75 cm (1957) to 135 cm (1981), that is, a little more than 0.5 meters in total. This agrees quite well with the literature data and estimates of other authors, considering the plain nature and small size of this object. The long-term course of the water levels of the Ikva River is characterized by a slight increase, while the long-term fluctuations of the average water flow at this station also do not have a large amplitude: from 0.66 m3/s (2020) to 3.64 m3/s (1979) i.e. 2.98 m3/s. At the same time, the general trend line for multi-year cost fluctuations shows, on the contrary, a tendency to decrease them. Therefore, we can state that the graphs of multi-year costs and levels are not synchronous, which is evidence of the manifestation of vertical channel deformations in the area of the post. As the water level increases, the decrease in water consumption is a direct sign of siltation of the riverbed in this area and the raising of the bottom level due to accumulative processes over a long period. The largest amplitudes are characterized by the parameters of the maximum runoff, that is, the amplitudes of the maximum levels (∆Нmax = 168 cm) and maximum flows (∆Qmax = 92.9 m3/s), which is not surprising, because we are talking about the characteristics of the period of floods and inundations, which are always marked by significant fluctuations in time. An interesting fact, identified for us for the first time, is that the characteristics of the minimum flow of the closed period of the channel are characterized by higher amplitudes than the characteristics of the open period. Therefore, the summer low water is more pronounced than the winter low water, which means that in the warm period (summer), the lack of precipitation more clearly provokes a decrease in water levels and flows in the channel system than during the winter period. The reason can be both winter thaws and the specifics of the groundwater regime. Key words: hydrological regime; water level; water flows; hydrological cycle; low water phase; high water phase; relationship Q=f(H).

Predicting the Impact of Climate Change on the Future Distribution of Paederus fuscipes Curtis, 1826, in China Based on the MaxEnt Model.

Paederus fuscipes Curtis, 1826, belongs to the Coleoptera order, Staphylinidae family, and Paederus genus (Fabricius, 1775). It has a wide distribution and strong invasive and environmental adaptation capabilities. As a predatory natural enemy of agricultural and forestry pests, understanding its suitable habitat is crucial for the control of other pests. This study, for the first time, uses the MaxEnt model and ArcGIS software, combining known distribution information of P. fuscipes and climate environmental factors to predict the current and future suitable habitat distribution of this insect. The key environmental variables affecting the distribution of P. fuscipes have been identified as mean diurnal range (mean of monthly (max temp-min temp)) (bio2), isothermality (Bio2/Bio7) (*100) (bio3), minimum temperature of the coldest month (bio6), temperature annual range (bio5-bio6) (bio7), mean temperature of the driest quarter (bio9), mean temperature of the coldest quarter (bio11), precipitation of the wettest month (bio13), precipitation of the driest month (bio14), and precipitation seasonality (coefficient of variation) (bio15). The highly suitable areas for P. fuscipes in China are mainly distributed in the hilly regions of Shandong, the North China Plain, and the middle and lower reaches of the Yangtze River Plain, with a total suitable area of 118.96 × 104 km2, accounting for 12.35% of China's total area. According to future climate change scenarios, it is predicted that the area of highly and lowly suitable regions will significantly decrease, while moderately suitable regions will increase (except for the 2090s, SSP2-4.5 scenario). These research findings provide important theoretical support for pest control and ecological conservation applications.

Influence of tundra fire severity on vegetation recovery in the Northwest Territories

Anthropogenic climate change has driven an increase in the frequency, size, and severity of fires at high latitudes. Recent research shows that increasing fire severity in the subarctic is altering the trajectories of forest succession, but to date, research on the effect of fire severity on tundra succession has been limited. In this study, we investigated short-term recovery of shrub tundra communities following fire in the Tuktoyaktuk Coastal Plain and Anderson River Plain ecoregions of the Northwest Territories. To understand the effects of fire severity, we documented vegetation and permafrost recovery within moderately burned, severely burned, and unburned portions of six tundra fires that burned in 2012. We found that vegetation structure at moderately and severely burnt sites recovered rapidly toward pre-fire levels, but that differences in community composition, characterized by a decrease in shrub and lichen cover as well as an increase in abundance of ruderals and graminoids, persisted at severely burned sites. The persistence of thermal changes and increased thaw depth indicate that while biotic recovery can occur promptly, severe fire may have long-term impacts on belowground conditions.

Experimental and numerical study of unsteady flows in a compound open channel

Unsteady flows are investigated in a compound open-channel flume, consisting of a Main Channel (MC) and an adjacent Flood Plain (FP). Two types of inflow hydrographs are studied, i.e., a discharge hydrograph with, at any time: a slightly unbalanced inflow partition between MC and FP (Case I); and a noticeably unbalanced inflow partition (Case II). Ensemble averages of the time-varying discharges, water depths and velocities are estimated based on 100 successive runs. The main focus of the experimental study is on assessing (i) the time-varying lateral discharge and depth-averaged Reynolds stress at the MC/FP interface, and (ii) the influence of the inflow partition on the downstream flow parameters. The experimental flows are then simulated using a 1D (one-dimensional) code that was adapted to implement the 1D+ Independent Sub-sections Model (ISM) (Proust et al. in Water Resour Res 45:1–16, 2009). The numerical study aims at validating the ISM under unsteady flow conditions, using classical 1D simulations as benchmark. It is experimentally found that 90 successive runs are required to get convergence of the ensemble averages of sub-section discharges and flow depth, while interfacial velocity is not fully converged after 100 runs. The influence of the inflow partition on the downstream parameters is felt along the whole flume. The ISM simulations are closer to the measurements than the classical 1D simulations. The ISM can accurately predict the time-varying flow depths and interfacial lateral discharge, and can approximate the interfacial Reynolds stresses.

Вплив геологічних структур на характер русел правобережних приток річки Дністер

The proposed study aims to determine the influence of geological structures on the features of the channels of the largest right-bank tributaries of the Dniester River - the Stryi, Bystrytsia, and Limnytsia rivers. For this purpose, we conducted zoning of the river based on morphometric and hydrological characteristics. Three parts were identified: mountainous, pre-mountainous area and plain area, which differ significantly in channel properties, their changes over time, and deformation processes. Objective. Based on remote sensing images of various resolutions, the use of historical maps over time, and specialized maps, to investigate the nature of the channels of the right-bank tributaries of the Dniester: Stryi, Limnytsia, and Bystrytsia, from their sources to the estuarine part where they flow into the Dniester River, depending on the geological and lithological features of the surface. The main research methods involve the transformation of various materials from remote sensing, historical, and special maps for the purpose of studying specific phenomena of river processes. The methodology involves the preparation of input materials, including historical topographic maps, geological maps, satellite images, maps and images georeferencing, satellite image processing, river channel vectorization, analysis of river channels depending on geological structures. Results. Considering the morphology, valley width, manifestation, and development of channel processes, the Stryi, Bystrytsia, and Limnytsia rivers were categorized into three sections: mountainous, pre-mountainous and plain area with developed accumulative forms. In the mountainous section, all three rivers have single channels, while in the pre-mountainous section, multichannel patterns are observed, which have decreased from the 19th to the 21st century in terms of the width of multichannelity and the number of channels. This indicates a decrease in the flow modulus. For the plain sections of channels with undeveloped accumulative forms, a clear tendency towards dependence of channel type on structural-lithological features is traced. Originality. The paper has established the dependence of channel processes of right-bank tributaries of the Dniester River on geological and sedimentological structures of the Skole Beskids and Subcarpathian Depression. Practical significance. The results of monitoring channel processes need to be considered in addressing a range of tasks, including the construction of hydraulic structures, designing power transmission networks at river crossings, developing gas pipelines, determining flood zones, assessing the consequences of erosion after floods, land reclamation, establishing water protection zones, managing recreational and border lands, and establishing interstate borders along rivers.

Developing a Fluvial and Pluvial Stochastic Flood Model of Southeast Asia

AbstractFlood event set generation, as employed in catastrophe risk models, relies on gauge information that is not available in data‐scarce regions. To overcome this limitation, we develop a stochastic fluvial and pluvial flood model of Southeast Asia, using freely and globally available discharge data from the global hydrological model GloFAS and rainfall from the ERA5 reanalysis. We use a conditional multivariate statistical model to produce a synthetic catalog of 10,000 years of flood events. We calculate the flood population exposure associated with each flood event using freely available population data from WorldPop and generate exposure probability exceedance curves. We validate the population exposure curves against observed flood disaster data from EM‐DAT, showing that our methodology provides exposure estimates that are in line with historical observations. We find that there is a 1% probability that more than 30 million people will be exposed to flooding in a given year according to our event set. This number is roughly half the population living in the 100‐year return period flood zone of Fathom's hazard maps, suggesting most studies based on static flood maps overestimate exposure. This analysis provides significant progress over previous non‐stochastic studies which are only able to compute total or average exposure within a given floodplain area and demonstrates that a reanalysis‐based stochastic flood model can be designed to generate reliable estimates of population exposure probability exceedance. This study is a step toward a fully global catastrophe model for floods capable of providing exposure and loss estimates worldwide.

Long-Term Response of Floodplain Meadow Normalized Difference Vegetation Index to Hydro-Climate and Grazing Pressure: Tamir River Plains, Mongolia

The greenery of floodplain meadows in arid regions, such as Mongolia, is influenced by climate, hydrology, and land use. In this study, we analyzed the NDVI (Normalized Difference Vegetation Index) of two floodplain meadows located along the South Tamir and Tamir Rivers using LANDSAT images. Our goal was to observe NDVI spatial changes, variations, and mean values in mid-August every six years from 1991 to 2015 and to identify the factors driving these differences. To achieve this, we conducted variance analysis to identify changes in NDVI and implemented Principal Component Analysis to determine the influence of hydro-meteorological factors and grazing intensity. Our findings indicate a significant decrease in greenness, as measured by pixel-scale NDVI, during the late summer period. This decrease was consistently observed, except for a series of harsh winters that followed relatively dry summers, resulting in a disastrous event called dzud, which led to the death of livestock. The decrease in NDVI was amplified by lower precipitation in June, higher temperatures and wind speed in July, and increased precipitation in August, along with a higher frequency of days with convective rain. Our findings have important implications for managing grazing in Mongolia’s grasslands, promoting sustainable land use, and mitigating sandstorms. The variance and average values of NDVI at the pixel level can serve as reliable markers of sustainable pasture management in areas where other vegetation measures are limited.