River Bed Elevation Research Articles

Assessing the possible influence of human activities on sediment transport in the Saskatchewan River and its delta

Sediment transport is a complex, multi-dimensional process. With the advancement in computing power and sophistication of computer applications over recent decades, it has become possible to conduct detailed analysis and simulations of soil erosion and sediment transport. The primary objective of this study was to examine and predict the potential influence of human activities on sediment transport. This was achieved by analyzing sediment transport in the Saskatchewan River beneath the E.B. Campbell Dam and in the Saskatchewan River Delta. The Hydrologic Engineering Center's-River Analysis System (HEC-RAS) was deployed to ascertain the sediment transport capacity and estimate erosion, sedimentation, and riverbed changes. Cross-sectional data, flow data, and sediment data were used in conjunction with HEC-RAS. The simulation results reveal that sediment transport below the E.B. Campbell Dam is limited, leading to notable sediment erosion. The selected study area has witnessed significant erosion during high-flow periods, particularly in the event of floods. Between 2012 and 2019, the riverbed elevation at the selected survey site decreased by approximately 0.45 m. The study findings corroborate that the Saskatchewan River and its delta have been impacted by human activities. Potential erosion and deposition below the E.B. Campbell Dam have been simulated for the selected site. The aim is to provide decision-makers or related stakeholders with insight into how dam operations can be adjusted to decrease erosion while sustaining hydrological, ecological, and environmental outcomes from human activities.

Modeling Riverbed Elevation and Bedload Tracer Transport Resting Times Using Fractional Laplace Motion

AbstractRiverbed elevations play a crucial role in sediment transport and flow resistance, making it essential to understand and quantify their effects. This knowledge is vital for various fields, including river engineering and stream ecology. Previous observations have revealed that fluctuations in the bed surface can exhibit both multifractal and monofractal behaviors. Specifically, the probability distribution function (PDF) of elevation increments may transition from Laplace (two‐sided exponential) to Gaussian with increasing scales or consistently remain Gaussian, respectively. These differences at the finest timescale lead to distinct patterns of bedload particle exchange with the bed surface, thereby influencing particle resting times and streamwise transport. In this paper, we utilize the fractional Laplace motion (FLM) model to analyze riverbed elevation series, demonstrating its capability to capture both mono‐ and multi‐fractal behaviors. Our focus is on studying the resting time distribution of bedload particles during downstream transport, with the FLM model primarily parameterized based on the Laplace distribution of increments PDF at the finest timescale. Resting times are extracted from the bed elevation series by identifying pairs of adjacent deposition and entrainment events at the same elevation. We demonstrate that in cases of insufficient data series length, the FLM model robustly estimates the tail exponent of the resting time distribution. Notably, the tail of the exceedance probability distribution of resting times is much heavier for experimental measurements displaying Laplace increments PDF at the finest scale, compared to previous studies observing Gaussian PDF for bed elevation.

Evaluation of Active and Passive UAV-Based Surveying Systems for Eulittoral Zone Mapping

Abstract. The eulittoral zone, which alternates between being exposed and submerged, presents a challenge for high-resolution characterization. Normally, its mapping is divided between low and high water levels, where each calls for a different type of surveying instrument. This leads to inconsistent mapping products, both in accuracy and resolution. Recently, uncrewed airborne vehicle (UAV) based photogrammetry was suggested as an available and low-cost solution. However, relying on a passive sensor, this approach requires adequate environmental conditions, while its ability to map inundated regions is limited. Alternatively, UAV-based topo-bathymetric laser scanners enable the acquisition of both submerged and exposed regions independent of lighting conditions while maintaining the acquisition flexibility. In this paper, we evaluate the applicability of such systems in the eulittoral zone. To do so, both topographic and topo-bathymetric LiDAR sensors were loaded on UAVs to map a coastal region along the river Rhein. The resulting point clouds were compared to UAV-based photogrammetric ones. Aspects such as point spacing, absolute accuracy, and vertical offsets were analysed. To provide operative recommendations, each LiDAR scan was acquired at different flying altitudes, while the photogrammetric point clouds were georeferenced based on different exterior information configurations. To assess the riverbed modelling, we compared the surface model acquired by the topo-bathymetric LiDAR sensor to multibeam echosounder measurements. Our analysis shows that the accuracies of the LiDAR point clouds are hardly affected by flying altitude. The derived riverbed elevation, on the other hand, shows a bias which is linearly related to water depth.

What drives uncertainty surrounding riverine flood risks?

Designing strategies to manage flood risks is complicated by the often large uncertainties surrounding flood risk projections. Uncertainty surrounding riverine flood risks can stem from choices regarding boundary and initial conditions, model structures, and parameters as well as interactions among hazards, exposures, and vulnerabilities. Here we analyze a case study to rank the drivers of uncertainties surrounding riverine flood hazards and risks. Using Sobol' sensitivity analysis with a large number of simulations, we thoroughly explore the interactions among different sources of uncertainty. We find that the projected flood risk is most sensitive to factors associated with flood hazards, rather than exposure and vulnerability: upstream discharge, river bed elevation, channel roughness, and the digital elevation model resolution. Our results highlight the importance of uncertainty quantification in enhancing the reliability of flood models and risk assessments.

LiDAR topo‐bathymetry for riverbed elevation assessment: A review of approaches and performance for hydrodynamic modelling of flood plains

AbstractTopo‐bathymetric LiDAR (TBL) can provide a continuous digital elevation model (DEM) for terrestrial and submerged portions of rivers. This very high horizontal spatial resolution and high vertical accuracy data can be promising for flood plain mapping using hydrodynamic models. Despite the increasing number of papers regarding the use of TBL in fluvial environments, its usefulness for flood mapping remains to be demonstrated. This review of real‐world experiments focusses on three research questions related to the relevance of TBL in hydrodynamic modelling for flood mapping at local and regional scales: (i) Is the accuracy of TBL sufficient? (ii) What environmental and technical conditions can optimise the quality of acquisition? (iii) Is it possible to predict which rivers would be good candidates for TBL acquisition? With a root mean square error (RMSE) of 0.16 m, results from real‐world experiments confirm that TBL provides the required vertical accuracy for hydrodynamic modelling. Our review highlighted that environmental conditions, such as turbidity, overhanging vegetation or riverbed morphology, may prove to be limiting factors in the signal's capacity to reach the riverbed. A few avenues have been identified for considering whether TBL acquisition would be appropriate for a specific river. Thresholds should be determined using geometric or morphological criteria, such as rivers with steep slopes, steep riverbanks, and rivers too narrow or with complex morphologies, to avoid compromising the quality or the extent of the coverage. Based on this review, it appears that TBL acquisition conditions for hydrodynamic modelling for flood mapping should optimise the signal's ability to reach the riverbed. However, further research is needed to determine the percentage of coverage required for the use of TBL as a source of bathymetry in a hydrodynamic model, and whether specific river sections must be covered to ensure model performance for flood mapping.

The analysis of degradation and aggradation of the riverbed: A case study of the Winongo River

The Winongo River, with a soil base, makes it possible to experience sedimentation events. In rivers with groundsill for retaining sediment rate, the flow can occur, grinding sediment (degradation) or aggradation on the riverbed. This study was conducted in Winongo River to see the effect of groundsill on riverbed degradation and aggradation levels. This research was carried out using the MPM, Engelund & Hansen, and Laursen-Copeland equations in HEC-RAS 6.3.1 by dividing Winongo River into 71 points with a spacing of ± 500 m, including nine with groundsills. Based on the effect of the groundsill on the riverbed, the cross sections at its upstream and downstream tend to experience quite different riverbed elevation changes. Conditions in the upstream groundsill tend to experience aggradation while the downstream experiences degradation. The three equations modelling results show that MPM and Engelund & Hansen equations are closer to field conditions than the Laursen-Copeland equation. The use of D50 sediment to model changes in riverbed elevation is more likely to experience degradation because the average grain size of D50 in this study sample was 0.82 mm.

Path length and sediment transport estimation from DEMs of difference: a signal processing approach

Abstract. The difficulties of measuring bedload transport in gravel-bed rivers have given rise to the morphological method wherein sediment transport can be inferred from changes in riverbed elevation and estimates of the distance traveled by sediment: its path length. Because current methods for estimating path length are time- and labor-intensive, we present a method to estimate a characteristic path length from repeat digital elevation models (DEMs of difference, i.e., DoDs). We propose an automated method to extract the spacing between erosional and depositional sites on the DoD by the application of variational mode decomposition (VMD), a signal processing method, to quantify the spacing as a proxy for path length. We developed this method using flume experiments where bed topography and sediment flux were measured and then applied it to published field data with physical path length measured from tracer measurements. Our sediment transport estimates were not significantly different than the measured sediment flux at lower discharges in the lab. However, we observed an underestimation of sediment flux at the higher discharges in the flume study. We interpret this as a limit of the method in confined settings, where sediment transport becomes decoupled from morphological changes. We also explore how the time between survey acquisitions, the morphological active width relative to the channel width, and DoD thresholding techniques affect the proposed method and the potential issues they pose for the morphological method in general.

The Effectiveness of Ground Sill Structure in Reducing Local Scouring at Cipamingkis River

Cipamingkis River is a subriver of Cibeet river located in Jonggol District, Bogor Regency, West Java Province. On the Cipamingkis river, there is a vital irrigation infrastructure known as the Cipamingkis Dam, which can irrigate approximately 4,591 hectares of rice fields in Bogor Regency and Bekasi Regency. Cipamingkis dam located in Jatinunggal Village, is on the northern slope of the West Java hills which has a relatively steep riverbed slope so that the possibility of degradation of the riverbed is relatively high. slope of the riverbed is relatively steep so that the possibility of riverbed degradation is quite high. riverbed degradation is quite high. In 2020 there were two Ground Sills that had been built upstream of the Cipamingkis weir. The Ground Sill built across the river aims to reduce the current velocity and increase the sediment deposition rate upstream of the Ground Sill so that the slope of the riverbed is relatively gentle and the Cipamingkis Dam does not experience structural failure as has happened before. The effectiveness is determined by comparing the riverbed elevation around the dam structure, before and after years construction of the Ground Sill structure.

PERBANDINGAN ELEVASI DASAR SUNGAI BERDASARKAN HASIL ANALISIS PADA DEM DRONE, DEMNAS dan DEM SRTM

Digital elevation models (DEMs) are essential to accurately predict river cross-section in the watershed. Technological developments of unmanned aerial vehicles (UAVs) or drone has received a lot of attention in various research field to get the latest information from the area, because of its mobility, high resolution, and low cost, so it can be a competitive alternative to produce maps with precise georeferences. However, this has not been tested so far. In this study, We evaluated the accuracy of the DEMs generated from UAV imagery by comparing it to DEMNAS, DEM SRTM, and direct topographic measurements. We performed regression analysis on the river bed elevation of the Kuranji River Padang, where the river bed elevation is the result of the analysis of each DEM. The result found that for river bed elevation of the DEM Drone performed competitively to DEMNAS with the correlation test value (r) were 0,992 and 0.954, respectively. The result of the DEM SRTM analysis has a wider range of data variations than the DEM Drone and DEMNAS.

Modeling probabilistic-based 1D riverbed elevation estimation model due to uncertainties in runoff and sediment-related factors

Abstract This study aims to develop a probabilistic model to quantify the reliability of estimating riverbed elevations due to the uncertainties in the runoff and sediment-related factors (named PM_MBEE_1D); the above uncertainties are quantified by reproducing a considerable number of runoff-related and sediment-related factors via the multivariate Monte Carlo simulation approach. Using a sizeable number of simulated uncertainty factors, the proposed PM_MBEE_1D model is developed by coupling the rainfall–runoff model (SAC-SMA) and 1D sediment transport simulation model (CCHE1D) with the uncertainty/risk analysis advanced first-order second-moment (AFOSM) method as well as the logistic regression analysis. Validated by the historical data in the Jhuosdhuei River watershed, the proposed PM_MBEE_1D model could efficiently and successfully capture the spatial and temporal changes in the estimated riverbed elevations (i.e., scouring and siltation) due to the uncertainties in the river runoff and sediment with a high accuracy (nearly 0.983). Also, using the proposed PM_MBEE_1D model with given runoff and sediment factors under a desired reliability, the probabilistic-based riverbed elevations could accordingly be estimated as a reference to watershed treatment and management plan.

Hydro-morphological alteration and related effects on fish habitat induced by sediment management in a regulated Alpine river

Sediment pulses can cause relevant geomorphological alteration and fine sediment deposition, affecting the entire river ecosystem. Quantifying the impact of these events is becoming increasingly important, as sediment disturbance is predicted to intensify because of growing anthropogenic activity combined to the effects of current climate change. In this paper, the effects of a sediment pulse event on riverbed morphology and, in turn, on fish habitat availability are assessed in a regulated river, located in the southern European Alps. Specifically, four target fish species were selected: marble (Salmo marmoratus) and brown trout (Salmo trutta), grayling (Thymallus thymallus), and bullhead (Cottus gobio). The investigated event was triggered by the effects of localized landslides combined with an uncontrolled sediment release from a hydropower reservoir. A pre-post event integrated approach was applied, involving topographic surveys, fine sediment deposition measurements, and eco-hydraulic modeling. Habitat availability analysis was done using two-dimensional steady-state channel-flow simulation and standard habitat suitability modeling, with univariate suitability curves as biological input. The investigation focused on two river reaches, quite close each other, but characterized by significantly different streamflow patterns, due to the layout of the local hydropower system. The results showed that noticeable riverbed fining occurred at both study reaches after the pulse, with the maximum thickness of the fine sediment deposits up to one meter, and higher amounts of deposition detected in areas wetted at baseflow. Moreover, for both reaches, recovery to the pre-event riverbed grain-size condition occurred in about a year, but with differences related to different streamflow patterns. Pre-post topographic comparison showed that areas of erosion prevailed over areas of deposition, and fine sediment deposition was not systematically associated to the riverbed elevation raise. Simulated habitat availability was affected by both topographic changes and fine sediment deposition, with the latter predominantly impacting juveniles and the most bottom dwelling species, i.e., the bullhead. The study confirms the need for improving the management of the hydro-sedimentary regime of regulated rivers to preserve the habitat of fish species, particularly of those characterized by conservation status already endangered.

Recent intensification of riverbed mining in the Mekong Delta revealed by extensive bathymetric surveying

Large-scale sand extraction has had significant and compounding impacts on the riverine environment of the Vietnamese Mekong Delta (VMD). Yet, effective and targeted implementation of regulations and sustainable management remains hindered by scant data availability, limiting a comprehensive understanding of the delta's sand mining scale and extent. This study assessed recent intensifying patterns of sand mining activities in the VMD mainly based on extensive bathymetric surveys carried out across 800 km2 of the VMD river channel from 2017 to 2022. Our results revealed severe riverbed deepening across the VMD, with the upper reaches of the Hau (Bassac) River experiencing an average incision of 1.4 m from 2017 to 2022, resulting in sediment losses of 127 Mm3. Similarly, the upper reaches of the Tien (Mekong) River and the Co Chien branch showed incisions of 1.3 m and 0.7 m from 2017 to 2020, accompanied by sediment losses of 139 Mm3 and 87 Mm3, respectively. The observed spatial and temporal variability in incisions, along with widespread sand mining pockmarks along the riverbed profiles, provide strong evidence of the significant contribution of sand mining to changes in riverbed morphology. The progressive lowering of riverbed elevation provides further evidence of the recent intensification of sand mining activities. Additionally, field surveys highlighted the proximity of perceived sites of bank collapse to pitted riverbeds, providing reliable indications of sand mining-induced erosion. Ultimately, we intend for this evidence-based assessment of sand mining activities in the VMD to contribute to informed quantitative assessments of sediment budgets and effective implementation of regulatory frameworks for sustainable sand mining in the future.

Calibrating a hydrodynamic model using water surface elevation determined from ICESat-2 derived cross-section and Sentinel-2 retrieved sub-pixel river width

Accurate observations of river water surface elevation (WSE) are critical for hydrodynamic (HD) model calibration in poorly gauged regions. This study presents a new river WSE retrieval approach that combines ICESat-2 derived cross-sections and Sentinel-2 observed sub-pixel river widths to achieve an effective HD model calibration. The unknown channel Manning coefficient, river bed elevation and cross-sectional shape in the HD model are calibrated simultaneously through a Bayesian optimization algorithm. The complete workflow is implemented in a flood-prone reach in Yiluo River basin. Results show that the WSE retrieved by the new approach has a higher spatiotemporal resolution in narrower rivers than that of Sentinel-3 altimetry derived WSE, and the root-mean-square error (RMSE) varies from 0.25 to 0.59 m against in-situ WSE. The HD model calibrated by WSE retrieved by the new approach simulates the WSE with RMSE of 0.36 m and the flood extent with critical success index (CSI) of 0.60 in validation, outperforming the results of the HD model calibrated by Sentinel-3 altimetry derived WSE, with corresponding results of 0.49 m and 0.58, respectively. Additional case studies in the Maqu and Lingkou reaches further demonstrate the applicability of the WSE retrieval approach proposed in this study for HD model calibration in different types of rivers. This study highlights the potential of the proposed WSE retrieval approach in HD model calibration to improve flood forecasting in poorly gauged regions.

Pengaruh Groundsill Pada Degradasi dan Agradasi Dasar Sungai Winongo (Studi Kasus Simulasi Dengan Sedimen D50)

One of the rivers in Yogyakarta with sand as its riverbed material is the Winongo River, which has a high potential for riverbed degradation or agradation. Upstream and downstream of the groundsill construction, respectively, can experience degradation and agradation of sediment transport. In this research, the effectiveness of the MPM, Engelund Hansen, and Laursen Copeland equations on HEC-RAS 6.3.1 is examined in terms of determining the level of overall degradation and agradation of the Winongo River bed. The discharge data used in modeling is in the form of secondary data taken from the 2021 DPUPESDM using two discharge conditions, namely wet discharge (Feb-Mar) and dry discharge (August-Sept). There are 796 cross sections along the river's 41.3 kilometer length, 9 of which are groundsill structures. For all equations, d50 serves as the grain diameter. Based on the results of the simulation, the upstream groundsill frequently agradation while the downstream groundsill tends to degradation. The MPM and Engelund Hansen equations are closer to actual field survey than the Laursen Copeland equation, according to the simulation using the three equations. The nine groundsills on the Winongo River still have the potential to harm the river bank by collapsing the downstream portion of the structure because the condition of degradation in the downstream groundsill is more prevalent than aggradation in the upstream groundsill. Due to the average d50 grain size, it is more likely that models used to predict changes in river bed elevation may degrade

Laboratory studies of the temporal evolution process of the riparian groundwater flow system related to rainfall

Comprehensive investigations of the riparian groundwater flow system response to rainfall based on laboratory experiments and numerical simulation are presented and discussed. The 1D sand column experiment results showed that the capillary fringe of the sand sample was 25 cm, and the supporting capillary water height was about 65 cm. The 2D sandbox was constructed to investigate the changes of hydraulic heads and groundwater flow system in the hypothetical riparian zone under different initial water tables and rainfall intensities. When the initial water table was shallow, a small amount of rainfall infiltration resulted in a rapid and large rise of the water table due to the effect of capillary fringe. When the initial water table was equal to the riverbed elevation, groundwater flow pattern changed once after the rainfall infiltration. In the early rainfall period, a groundwater divide and two opposite local flow systems occurred; one flowed to the upslope unsaturated zone (counter directional local flow system), the other flowed to the river (codirectional local flow system). As the rain continued, the groundwater divide kept moving to the upslope and finally disappeared by forming a stable codirectional regional flow system. When the initial water table was lower than the riverbed, groundwater flow pattern was more complex and changed twice. At the beginning, all the rainfall infiltration recharged the thick unsaturated zone and there was only a counter directional regional flow system. When the water table rose to the riverbed, a groundwater divide and two opposite local flow systems were formed. The groundwater divide was moving to the upland and finally formed a steady codirectional regional flow system. More fine characterization of hydrological variation in a short-time scale in the riparian zone is necessary in the future.

Morphological changes analysis using 3D bathymetric surveys in Chilia Branch - Bystroe Channel bifurcation area

The Bystroe Channel project with transboundary environmental impact in the Danube Delta, area of great ecological significance that has already a strong anthropic footprint, requires close monitoring of water quality parameters in order to determine their tendencies and their impact on the ecosystem components. Riverbed bathymetry surveys using multibeam echo-sounders are of high interest due to the data resolution and coverage capabilities that surpass the single-beam methods. Two riverbed elevation datasets, recorded in consecutive years, have been used to carry out morphological comparative analysis for the area where Chilia branch bifurcates in Bystroe Channel and Old Stambul. The analysis has been performed both on the bathymetry grids as a whole and on 3 longitudinal and 9 transversal river sections, the morphological changes values being in majority included in [-0.5 m;+0.5 m], with a minimum of -2.4 m and a maximum of 2.2 m, showing the bifurcation influence on the erosion/deposition processes results.

Towards an AI-based early warning system for bridge scour

ABSTRACT Scour is the number one cause of bridge failure in many parts of the world. Considering the lack of reliability in existing empirical equations for scour depth estimation and the complexity and uncertainty of scour as a physical phenomenon, it is essential to develop more reliable solutions for scour risk assessment. This study introduces a novel AI approach for early forecast of scour based on real-time monitoring data obtained from sonar and stage sensors installed at bridge piers. Long-short Term Memory networks (LSTMs), a prominent Deep Learning algorithm successfully used for time-series forecasting in other fields, were developed and trained using river stage and bed elevation readings for more than 11 years, obtained from Alaska scour monitoring programme. The capability of the AI models in scour prediction is shown for three case-study bridges. Results show that LSTMs can capture the temporal and seasonal patterns of both flow and river bed variations around bridge piers, through cycles of scour and filling and can provide reasonable predictions of upcoming scour depth as early as seven days in advance. It is expected that the proposed solution can be implemented by transportation authorities for development of emerging AI-based early warning systems, enabling superior bridge scour management.

Discrete Analysis of Local Scour Morphology of Bridge Piers Affected by Sediment Storage Dam

In order to solve the prediction and protection problems of local pier scour with a downstream sediment storage dam on non-uniform sand riverbeds in mountainous areas, the Xi’an Chanhe Bridge in China was taken as the research object. Through comprehensive physical model experiments, the influence of sediment storage dam layout on the surrounding water flow and local scour morphology around bridge piers was studied. The relationship between boundary conditions and local scour pit morphology was studied using a discrete analysis model. The research results showed that the inflow rate Q was the most significant factor affecting local scour, and local scour generally developed rapidly within 0.5–1.0 h and then gradually reached a dynamic equilibrium. The maximum depth was located within 0.25B in front of the pier relative to the pier width , and the impact range of local scour behind the pier was [5B, 10B] . The recommended layout of a sediment storage dam has a distance between pier and dam L of [8B,11B] and a dam crest elevation Z higher than that of the original riverbed elevation at the bridge pier, which is [0.4B, 0.5B]. An improved calculation formula for the local scour depth of bridge piers is proposed and verified through experimental measurements to provide a reference for the design and protection of bridge piers with a downstream sediment storage dam.Q

A surface and ground‐water integrated investigation of streamflow drying up in semi‐arid regions

AbstractGroundwater exploitations in semi‐arid regions result in significant declines of groundwater levels and streamflow and even trigger seasonal streamflow drying up, which may bring adverse impacts on riparian ecosystems. It is critical to explore future streamflow changes caused by variable climate scenarios and groundwater exploitation intensities; however, a comprehensive assessment of the streamflow drying up frequency remains lacking. Furthermore, the thresholds of controlling factors beyond which streamflow drying up occurs have rarely been explored. Here we develop an integrated surface water‐groundwater model for the Taoer River Basin (TRB), a typical semi‐arid watershed in northeast China. We apply the model to multiple future scenarios to reveal the frequency of potential streamflow drying up and explore the thresholds of controlling factors of streamflow drying up based on a decision tree method. We find that the groundwater level in the lower region of the TRB (LTRB) is hard to recover to the riverbed elevation and the streamflow drying up frequency is still high unless the groundwater exploitation is reduced by 50%. However, this leads to a competition between the ecological and economic objectives. Our results also show that the streamflow drying up frequency in the LTRB is very sensitive to the upstream water inflow that can be regulated through the reservoir operation or inter‐basin water diversion, indicating the importance of a basin scale strategic management. The findings of this paper can help policy makers sustainably exploit water resources in semi‐arid regions.

Preliminary study on the mechanism underlying the ecological isolation of Oncomelania hupensis populations in Changde City

To investigate ecological isolation between Oncomelania hupensis snail populations in hilly regions and marshland and lake regions in Yuanjiang valley, Changde City, Hunan Province, and to unravel its underlying mechanisms. Taoyuan County, Shimen County, Linli County and Lixian County in Changde City were selected as snail sampling sites in hilly regions, and Lixian County, Jinshi City, West Lake Administration District, Hanshou County and Dingcheng District were selected as snail sampling sites in marshland and lake areas. Cytochrome C oxidase 1 (cox 1) gene was amplified in snail samples and sequenced. The genetic sequences of O. hupensis snails were aligned using the software MEGA 11, and the haplotypes of O. hupensis snails were determined using the software DNASP 5.10.01. The phylogenetic tree was generated using Bayesian inference with the software MrBayes 3.2, and analysis of molecular variance (AMOVA) was performed to analyze the source of genetic divergence and estimate the genetic divergence index (FST) among snail populations with the software Arlequin 3.5.2.2. The genetic barrier among 11 O. hupensis snail populations was estimated using the Monmonier algorithm of adegenet toolkit in R package. The settings with "land in winter and water in summer" in the Yuanjian River section were divided into two categories according to the upstream and downstream, and the areas with "land in winter and water in summer" in the upstream and downstream were transformed into raster data, and then loaded into the software Fragstats 4 for analysis of landscape indicators. The trends in changes of digital elevation were extracted from the Yuanjiang River section based on the digital elevation model, and made three-dimensional visualization using the R package. The mitochondrial cox 1 gene were amplified in 165 O. hupensis snais from 11 sampling sites and sequenced, and a total of 152 valid gene sequences were obtained, with 46 haplotypes or 9 populations determined. No haplotype was shared in snails between Taoyuan County and Dingcheng District and Hanshou County along the downstream of the Yuanjiang River. The total area of settings with "land in winter and water in summer" was 617.66 hm2 in the upsteram of the Yuanjiang River, which consisted of 473 patches, with each patch measuring 1.31 hm2, the largest area index of 0.735 2, the landscape division index of 0.999 9, and the landscape shape index of 45.293 7. The total area of settings with "land in winter and water in summer" was 9 956.92 hm2 in the downstream of the Yuanjiang River, which consisted of 771 patches, with each patch measuring 12.91 hm2, the largest area index of 97.839 9, the landscape division index of 0.042 7, and the landscape shape index of 7.249 6. The area of settings with "land in winter and water in summer" was much larger in the downstream than that in the upstream of the Yuanjiang River, and the stronger landscape connectivity and non-remarkable alteration of riverbed elevation provided suitable habitats for snail breeding. The hydrological and environmental characteristics of the upstream of the Yuanjiang River restrain the breeding and spread of O. hupensis, resulting in ecological isolation between Oncomelania hupensis in Taoyuan County and those in the downstream of Yuanjiang River.