Pub Date : 2024-09-20DOI: 10.1016/j.ijsrc.2024.08.004
Li He , Hang Yin , Yongkang Wu , Wei Sun , Guoping Zhang
The response of suspended tenuous clay-polysaccharide flocs to hydrodynamic shearing was investigated in the laboratory via particle size analyses to understand the molecular-scale interactions between clay minerals and polysaccharides and their hydrodynamic behavior such as size kinetics, re-flocculation/breakdown, and shear strengths of the hybrid flocs. While the studied suspensions had a fixed clay concentration of 0.4 g/L, an array of other parameters was varied to reflect the complexity of clay-polysaccharide systems, including four types of clay minerals with varying layer charges and swellability (i.e., kaolinite, illite, and sodium- (Na-) and calcium- (Ca-) montmorillonites), two exopolymers of dissimilar polarities (i.e., xanthan and guar), six polysaccharide (P) to clay (C) weight ratios (i.e., P/C = 0, 1, 2, 5, 10, and 20 wt%), and three hydrodynamic shearing rates of 187, 429, and 1,100 1/s (i.e., corresponding to laminar, transitional, and turbulent flows, respectively). Results show that the clay-polysaccharide floc sizes are sensitive to the shear stress and also vary with different clay-polysaccharide systems. Four discrete particle groups were identified by statistical analyses, consisting of primary particle (PP), flocculi (FL), microfloc (MiF), and macrofloc (MaF), which exhibit distinct stabilities to shearing. The MaF is much weaker than MiF and can easily breakdown, as indicated by the decrease in MaF fraction with increasing shearing, while the MiF is the dominant particle group in transitional and turbulent flows. The fractions of PP and FL generally increase with shearing rate. Based on floc survivability in different flow conditions, the MaF's upper and lower bound shear strengths were estimated to be 0.95 and 0.17 Pa, respectively. The strongest MaF with a maximum shear strength of 0.95 Pa is formed in the clay-guar suspensions at a P/C of 10 wt%. Anionic xanthan only forms flocs with kaolinite with little surface charges, but cannot induce clay-polysaccharide flocs for illite and Ca/Na-montmorillonite with negative surface charges due to electrostatic repulsion. In contrast, neutral guar generates flocs with all 4 clay minerals due to the formation of hydrogen bonds, and MaF compounds usually are absent in turbulent flow (except kaolinite with a small fraction of MaF). These results further demonstrate the essential role of polysaccharide's polarity in dictating the flocculation dynamics, and, hence, sediment transport behavior. Practical implications of the findings are discussed in terms of the emerging technological applications of clay-polymer systems as well as the transport and modeling of natural aquatic cohesive sediment in biofilm-bearing waters.
{"title":"Response of tenuous clay-polysaccharide flocs to hydrodynamic shearing","authors":"Li He , Hang Yin , Yongkang Wu , Wei Sun , Guoping Zhang","doi":"10.1016/j.ijsrc.2024.08.004","DOIUrl":"10.1016/j.ijsrc.2024.08.004","url":null,"abstract":"<div><div>The response of suspended tenuous clay-polysaccharide flocs to hydrodynamic shearing was investigated in the laboratory via particle size analyses to understand the molecular-scale interactions between clay minerals and polysaccharides and their hydrodynamic behavior such as size kinetics, re-flocculation/breakdown, and shear strengths of the hybrid flocs. While the studied suspensions had a fixed clay concentration of 0.4 g/L, an array of other parameters was varied to reflect the complexity of clay-polysaccharide systems, including four types of clay minerals with varying layer charges and swellability (i.e., kaolinite, illite, and sodium- (Na-) and calcium- (Ca-) montmorillonites), two exopolymers of dissimilar polarities (i.e., xanthan and guar), six polysaccharide (<em>P</em>) to clay (<em>C</em>) weight ratios (i.e., <em>P</em>/<em>C</em> = 0, 1, 2, 5, 10, and 20 wt%), and three hydrodynamic shearing rates of 187, 429, and 1,100 1/s (i.e., corresponding to laminar, transitional, and turbulent flows, respectively). Results show that the clay-polysaccharide floc sizes are sensitive to the shear stress and also vary with different clay-polysaccharide systems. Four discrete particle groups were identified by statistical analyses, consisting of primary particle (PP), flocculi (FL), microfloc (MiF), and macrofloc (MaF), which exhibit distinct stabilities to shearing. The MaF is much weaker than MiF and can easily breakdown, as indicated by the decrease in MaF fraction with increasing shearing, while the MiF is the dominant particle group in transitional and turbulent flows. The fractions of PP and FL generally increase with shearing rate. Based on floc survivability in different flow conditions, the MaF's upper and lower bound shear strengths were estimated to be 0.95 and 0.17 Pa, respectively. The strongest MaF with a maximum shear strength of 0.95 Pa is formed in the clay-guar suspensions at a <em>P</em>/<em>C</em> of 10 wt%. Anionic xanthan only forms flocs with kaolinite with little surface charges, but cannot induce clay-polysaccharide flocs for illite and Ca/Na-montmorillonite with negative surface charges due to electrostatic repulsion. In contrast, neutral guar generates flocs with all 4 clay minerals due to the formation of hydrogen bonds, and MaF compounds usually are absent in turbulent flow (except kaolinite with a small fraction of MaF). These results further demonstrate the essential role of polysaccharide's polarity in dictating the flocculation dynamics, and, hence, sediment transport behavior. Practical implications of the findings are discussed in terms of the emerging technological applications of clay-polymer systems as well as the transport and modeling of natural aquatic cohesive sediment in biofilm-bearing waters.</div></div>","PeriodicalId":50290,"journal":{"name":"International Journal of Sediment Research","volume":"39 6","pages":"Pages 984-997"},"PeriodicalIF":3.5,"publicationDate":"2024-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142662560","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The ancient city of Phaselis, which is located along gravel, coarse sandy, and sandy beaches, is a popular area visited by thousands of domestic and foreign tourists every year, and has been selected as the study area. Sediment samples collected from 57 different locations in the ancient city of Phaselis were analyzed using an X-ray fluorescence (XRF) spectrometer, and the major, trace, and rare earth element contents of the samples were revealed. The heavy metals arsenic (As), cobalt (Co), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), tin (Sn), stronsium (Sr), and zinc (Zn) were used in the pollution index calculations. Distribution maps revealed that heavy metal concentrations reached higher levels, especially in the eastern part of the study area. Therefore, it is recommended to plant rooted macrophytes that can absorb the heavy metals Cr and Ni and perform phytoremediation of the sediment in the region.
法塞里斯古城位于砾石滩、粗沙滩和沙滩沿岸,是每年有成千上万国内外游客到访的热门地区,因此被选为研究区域。研究人员使用 X 射线荧光光谱仪(XRF)对从法塞利斯古城 57 个不同地点采集的沉积物样本进行了分析,揭示了样本中主要元素、痕量元素和稀土元素的含量。重金属砷(As)、钴(Co)、铬(Cr)、铜(Cu)、镍(Ni)、铅(Pb)、锡(Sn)、锶(Sr)和锌(Zn)被用于污染指数计算。分布图显示,重金属浓度达到较高水平,尤其是在研究区域的东部。因此,建议在该地区种植能吸收重金属铬和镍的根系大型植物,对沉积物进行植物修复。
{"title":"Source identification of heavy metal contamination in beach sediments of the ancient city of Phaselis in Antalya, Türkiye","authors":"Ozge Ozer Atakoglu , Emirhan Berberoglu , Fusun Yalcin , Serife Gokaydin , Ebru Akkopru , Mustafa Gurhan Yalcin","doi":"10.1016/j.ijsrc.2024.09.003","DOIUrl":"10.1016/j.ijsrc.2024.09.003","url":null,"abstract":"<div><div>The ancient city of Phaselis, which is located along gravel, coarse sandy, and sandy beaches, is a popular area visited by thousands of domestic and foreign tourists every year, and has been selected as the study area. Sediment samples collected from 57 different locations in the ancient city of Phaselis were analyzed using an X-ray fluorescence (XRF) spectrometer, and the major, trace, and rare earth element contents of the samples were revealed. The heavy metals arsenic (As), cobalt (Co), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), tin (Sn), stronsium (Sr), and zinc (Zn) were used in the pollution index calculations. Distribution maps revealed that heavy metal concentrations reached higher levels, especially in the eastern part of the study area. Therefore, it is recommended to plant rooted macrophytes that can absorb the heavy metals Cr and Ni and perform phytoremediation of the sediment in the region.</div></div>","PeriodicalId":50290,"journal":{"name":"International Journal of Sediment Research","volume":"39 6","pages":"Pages 942-959"},"PeriodicalIF":3.5,"publicationDate":"2024-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142662600","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-06DOI: 10.1016/j.ijsrc.2024.09.001
Enqi Yang , Qingzheng Wang , Zepeng Zhang , Wenyan Shao , Haiping Luo , Xiong Xiao , Fei Ni , Jimin Mi , Xiazhong Sun , Qingyu Guan
Heavy metals can easily accumulate in soil and river sediment due to their non-degradability, which seriously endangers the balance of the ecosystem and human health. Thus, research on heavy metals in soil-river composite ecosystems has great significance for risk mitigation. As a seasonal river in a semi-arid region (Yuzhong county) in northwest China, the Wanchuan River supports nearly 500,000 people, but has been polluted by the heavy metals from industrial wastes and sewage discharges. To protect precious water resources and soil ecosystems, it is urgent to do heavy metal research in the Wanchuan River basin. Towards this end, the current study collected samples of soil and river sediment in this basin, and analyzed the distribution characteristics, health risks, and pollution sources of heavy metals, based on the pollution index evaluation method, health risk assessment, a geostatistical model, and the positive matrix factorization (PMF) model. The research results show that the contents of heavy metals in soil and river sediment were equivalent. However, contamination levels of heavy metals in stream sediment fell below that in soil. The results from the PMF model pointed out that natural sources contributed remarkably to the contents of heavy metals in soil, while industrial sources had the highest contribution to the contents of heavy metals in river sediment. According to the health risk assessment, among all selected metals, Cr brought about the highest carcinogenic risk, while As generated the highest non-carcinogenic risk. Source-oriented health risk assessment showed that natural sources (37%) and agricultural sources (50%), respectively, contributed most to the non-carcinogenic risks and carcinogenic risks induced by soil metals. Industrial sources contributed most both to the non-carcinogenic risks (46%) and carcinogenic risks (37%) induced by river sediment metals. The current research may offer theoretical bases for heavy metal pollution treatment in the soil-river continuum.
{"title":"Source-oriented health risk assessment of heavy metals in a soil-river continuum in northwest China","authors":"Enqi Yang , Qingzheng Wang , Zepeng Zhang , Wenyan Shao , Haiping Luo , Xiong Xiao , Fei Ni , Jimin Mi , Xiazhong Sun , Qingyu Guan","doi":"10.1016/j.ijsrc.2024.09.001","DOIUrl":"10.1016/j.ijsrc.2024.09.001","url":null,"abstract":"<div><div>Heavy metals can easily accumulate in soil and river sediment due to their non-degradability, which seriously endangers the balance of the ecosystem and human health. Thus, research on heavy metals in soil-river composite ecosystems has great significance for risk mitigation. As a seasonal river in a semi-arid region (Yuzhong county) in northwest China, the Wanchuan River supports nearly 500,000 people, but has been polluted by the heavy metals from industrial wastes and sewage discharges. To protect precious water resources and soil ecosystems, it is urgent to do heavy metal research in the Wanchuan River basin. Towards this end, the current study collected samples of soil and river sediment in this basin, and analyzed the distribution characteristics, health risks, and pollution sources of heavy metals, based on the pollution index evaluation method, health risk assessment, a geostatistical model, and the positive matrix factorization (PMF) model. The research results show that the contents of heavy metals in soil and river sediment were equivalent. However, contamination levels of heavy metals in stream sediment fell below that in soil. The results from the PMF model pointed out that natural sources contributed remarkably to the contents of heavy metals in soil, while industrial sources had the highest contribution to the contents of heavy metals in river sediment. According to the health risk assessment, among all selected metals, Cr brought about the highest carcinogenic risk, while As generated the highest non-carcinogenic risk. Source-oriented health risk assessment showed that natural sources (37%) and agricultural sources (50%), respectively, contributed most to the non-carcinogenic risks and carcinogenic risks induced by soil metals. Industrial sources contributed most both to the non-carcinogenic risks (46%) and carcinogenic risks (37%) induced by river sediment metals. The current research may offer theoretical bases for heavy metal pollution treatment in the soil-river continuum.</div></div>","PeriodicalId":50290,"journal":{"name":"International Journal of Sediment Research","volume":"39 6","pages":"Pages 916-928"},"PeriodicalIF":3.5,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142247354","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-03DOI: 10.1016/j.ijsrc.2024.09.002
Enhui Jiang , Junhua Li , Yongtao Cao , Yanhui Liu , Yuanjian Wang , Qiang Wan , Li Pan
River-bottom tearing scour (RBTS) in natural rivers refers to the incipient motion and transport processes of clay blocks formed by fine cohesive sediment after deposition and consolidation in riverbeds. The RBTS phenomenon can lead to significant channel erosion and changes in river planview morphology, and has, thus, attracted the attention of hydrologists and engineers. In the study, a new determination measure (K) for the occurrence of a RBTS event is derived based on the theoretical expression for the critical incipient velocity of the clay block, , which is a combination of the coefficients of the velocity (i.e., is a local velocity coefficient), lift force (i.e., CL is the lift coefficient), and clay block size (i.e., is the ratio of block thickness to length). Furthermore, to explain river behavior during a RBTS event, the Fugu, Xiaobeiganliu, and Weihe river reaches in the Middle Yellow River (MYR) were selected as study areas. Analysis of hydrological data from 1950 to 2023 in the examined reaches implies that a single discharge or sediment threshold cannot predict the occurrence of RBTS. The cross-sectional erosion and deposition volume (CEDV) and the migration intensity of the channel thalweg (MI) also were calculated at the section and reach scales for the examined reaches during the RBTS events. It was observed that RBTS typically causes significant channel erosion originating from the most upstream portion of the study reach with CEDV values ranging from 61 to 6034 m2, while MI values during the RBTS events were close to the multi-year average for the study reach. Finally, a flume experiment simulating RBTS was done to discuss and verify the threshold value of K. Field survey and experimental results indicated that RBTS occurs if K > 0.5, thus, providing theoretical support for the prediction and prevention of RBTS.
{"title":"Defining and characterizing the phenomenon of river-bottom tearing scour (RBTS): A case study of the Middle Yellow River","authors":"Enhui Jiang , Junhua Li , Yongtao Cao , Yanhui Liu , Yuanjian Wang , Qiang Wan , Li Pan","doi":"10.1016/j.ijsrc.2024.09.002","DOIUrl":"10.1016/j.ijsrc.2024.09.002","url":null,"abstract":"<div><div>River-bottom tearing scour (RBTS) in natural rivers refers to the incipient motion and transport processes of clay blocks formed by fine cohesive sediment after deposition and consolidation in riverbeds. The RBTS phenomenon can lead to significant channel erosion and changes in river planview morphology, and has, thus, attracted the attention of hydrologists and engineers. In the study, a new determination measure (<em>K</em>) for the occurrence of a RBTS event is derived based on the theoretical expression for the critical incipient velocity of the clay block, <span><math><mrow><mi>K</mi><mo>=</mo><msup><mrow><mspace></mspace><mi>α</mi></mrow><mn>2</mn></msup><mrow><mo>(</mo><mrow><msub><mi>C</mi><mi>L</mi></msub><mo>+</mo><mn>2</mn><msubsup><mi>λ</mi><mn>2</mn><mn>2</mn></msubsup></mrow><mo>)</mo></mrow></mrow></math></span>, which is a combination of the coefficients of the velocity (i.e., <span><math><mrow><mi>α</mi></mrow></math></span> is a local velocity coefficient), lift force (i.e., <em>C</em><sub>L</sub> is the lift coefficient), and clay block size (i.e., <span><math><mrow><msub><mi>λ</mi><mn>2</mn></msub></mrow></math></span> is the ratio of block thickness to length). Furthermore, to explain river behavior during a RBTS event, the Fugu, Xiaobeiganliu, and Weihe river reaches in the Middle Yellow River (MYR) were selected as study areas. Analysis of hydrological data from 1950 to 2023 in the examined reaches implies that a single discharge or sediment threshold cannot predict the occurrence of RBTS. The cross-sectional erosion and deposition volume (CEDV) and the migration intensity of the channel thalweg (MI) also were calculated at the section and reach scales for the examined reaches during the RBTS events. It was observed that RBTS typically causes significant channel erosion originating from the most upstream portion of the study reach with CEDV values ranging from 61 to 6034 m<sup>2</sup>, while MI values during the RBTS events were close to the multi-year average for the study reach. Finally, a flume experiment simulating RBTS was done to discuss and verify the threshold value of <em>K</em>. Field survey and experimental results indicated that RBTS occurs if <em>K</em> > 0.5, thus, providing theoretical support for the prediction and prevention of RBTS.</div></div>","PeriodicalId":50290,"journal":{"name":"International Journal of Sediment Research","volume":"39 6","pages":"Pages 929-941"},"PeriodicalIF":3.5,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142247385","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Soil erosion is considered one of the most prevalent natural hazards in semiarid regions, leading to the instability of ecosystems and human life. The main purpose of this research was to investigate and analyze soil erosion susceptibility maps in the Medjerda basin in northern Africa. This study utilizes four ensemble models based on the analytical hierarchy process (AHP) multicriteria decision-making analysis, namely, deep learning neural network AHP (DLNN-AHP), frequency ratio AHP (FR-AHP), Monte Carlo AHP (MC-AHP), and fuzzy AHP (F-AHP). Eight predictor variables were considered as inputs to the model, namely, the slope degree, digital elevation model (DEM), topographic wetness index (TWI), distance to river (DFR), distance to road (DFRD), normalized difference vegetation index (NDVI), rainfall erosivity (R), factor and soil erodibility factor (K). Soil erosion inventory maps were developed from field surveys and satellite images. The dataset was randomly divided into 70% for training and 30% for testing. The performances of the utilized models were compared using a receiver operating characteristic (ROC) curve. The results highlighted that all the models utilized exhibited good performance, with DLNN-AHP (93.1%) exhibiting slight superiority, followed by FR-AHP (90.9%), F-AHP (88.9%), and MC-AHP (88.5%). Among the influencing factors, the distance to the river and rainfall erosivity had the most significant impacts on the incidence of soil erosion. Moreover, the current findings revealed that 38.3% of the study area is extremely highly susceptible to soil erosion. The results of this study can aid in developing decision-support tools for planners and managers aiming to mitigate the adverse effects of soil erosion.
{"title":"Soil erosion susceptibility prediction using ensemble hybrid models with multicriteria decision-making analysis: Case study of the Medjerda basin, northern Africa","authors":"Asma Bouamrane , Hamouda Boutaghane , Ali Bouamrane , Noura Dahri , Habib Abida , Mohamed Saber , Sameh A. Kantoush , Tetsuya Sumi","doi":"10.1016/j.ijsrc.2024.08.003","DOIUrl":"10.1016/j.ijsrc.2024.08.003","url":null,"abstract":"<div><div>Soil erosion is considered one of the most prevalent natural hazards in semiarid regions, leading to the instability of ecosystems and human life. The main purpose of this research was to investigate and analyze soil erosion susceptibility maps in the Medjerda basin in northern Africa. This study utilizes four ensemble models based on the analytical hierarchy process (AHP) multicriteria decision-making analysis, namely, deep learning neural network AHP (DLNN-AHP), frequency ratio AHP (FR-AHP), Monte Carlo AHP (MC-AHP), and fuzzy AHP (F-AHP). Eight predictor variables were considered as inputs to the model, namely, the slope degree, digital elevation model (DEM), topographic wetness index (TWI), distance to river (DFR), distance to road (DFRD), normalized difference vegetation index (NDVI), rainfall erosivity (<em>R</em>), factor and soil erodibility factor (<em>K</em>). Soil erosion inventory maps were developed from field surveys and satellite images. The dataset was randomly divided into 70% for training and 30% for testing. The performances of the utilized models were compared using a receiver operating characteristic (ROC) curve. The results highlighted that all the models utilized exhibited good performance, with DLNN-AHP (93.1%) exhibiting slight superiority, followed by FR-AHP (90.9%), F-AHP (88.9%), and MC-AHP (88.5%). Among the influencing factors, the distance to the river and rainfall erosivity had the most significant impacts on the incidence of soil erosion. Moreover, the current findings revealed that 38.3% of the study area is extremely highly susceptible to soil erosion. The results of this study can aid in developing decision-support tools for planners and managers aiming to mitigate the adverse effects of soil erosion.</div></div>","PeriodicalId":50290,"journal":{"name":"International Journal of Sediment Research","volume":"39 6","pages":"Pages 998-1014"},"PeriodicalIF":3.5,"publicationDate":"2024-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142186086","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-22DOI: 10.1016/j.ijsrc.2024.06.005
Xin Liu , Junqiang Xia , Shanshan Deng , Meirong Zhou , Koen Blanckaert
In what kind of meanders concave-bank deposition (CBD) can occur remains an open question. This study investigated the characteristics and major influencing factors of CBD in the meanders of the Middle Yangtze River (MYR), and proposed a formation condition for CBD. Concave-bank deposition occurred in 10 of 23 meanders in the MYR, including two types: counter point bar (CPB) and concave-bank bench (CBB). CPB occurred in both mildly-curved and sharp bends, while CBB only occurred in sharp bends. Hydrodynamic conditions and sediment supply are two major factors controlling the formation of CBD. The incoming sediment load remained in an amount of 0.68 × 108 t/y at Jianli and 0.77 × 108 t/y at Luoshan after Three Gorges Project operation, therefore, CBD development was not limited by a lack of sediment and instead is mainly dependent on the hydrodynamic conditions in the MYR. Flow separation zones were observed in the typical CBD-type bends of the MYR, which indicated that CBD was the result of flow separation or recirculation. An adverse longitudinal water surface gradient is the necessary condition for the formation of concave-bank flow separation. Therefore, a formation condition for CBD was proposed based on this assumption, which considered the combined effects of channel resistance, riverbed slope, channel widening, and curvature. CBD happens when the channel widening and curvature terms are greater than the channel resistance and longitudinal channel slope terms. The proposed condition was verified based on the data of the 23 bends in the MYR and 26 bends in 12 other rivers. The results indicated that more than 85% of the bends were correctly identified. Therefore, the proposed formation condition provided considerably high accuracy.
{"title":"Formation condition for concave-bank deposition in the meanders of the Middle Yangtze River and its application","authors":"Xin Liu , Junqiang Xia , Shanshan Deng , Meirong Zhou , Koen Blanckaert","doi":"10.1016/j.ijsrc.2024.06.005","DOIUrl":"10.1016/j.ijsrc.2024.06.005","url":null,"abstract":"<div><div>In what kind of meanders concave-bank deposition (CBD) can occur remains an open question. This study investigated the characteristics and major influencing factors of CBD in the meanders of the Middle Yangtze River (MYR), and proposed a formation condition for CBD. Concave-bank deposition occurred in 10 of 23 meanders in the MYR, including two types: counter point bar (CPB) and concave-bank bench (CBB). CPB occurred in both mildly-curved and sharp bends, while CBB only occurred in sharp bends. Hydrodynamic conditions and sediment supply are two major factors controlling the formation of CBD. The incoming sediment load remained in an amount of 0.68 × 10<sup>8</sup> t/y at Jianli and 0.77 × 10<sup>8</sup> t/y at Luoshan after Three Gorges Project operation, therefore, CBD development was not limited by a lack of sediment and instead is mainly dependent on the hydrodynamic conditions in the MYR. Flow separation zones were observed in the typical CBD-type bends of the MYR, which indicated that CBD was the result of flow separation or recirculation. An adverse longitudinal water surface gradient is the necessary condition for the formation of concave-bank flow separation. Therefore, a formation condition for CBD was proposed based on this assumption, which considered the combined effects of channel resistance, riverbed slope, channel widening, and curvature. CBD happens when the channel widening and curvature terms are greater than the channel resistance and longitudinal channel slope terms. The proposed condition was verified based on the data of the 23 bends in the MYR and 26 bends in 12 other rivers. The results indicated that more than 85% of the bends were correctly identified. Therefore, the proposed formation condition provided considerably high accuracy.</div></div>","PeriodicalId":50290,"journal":{"name":"International Journal of Sediment Research","volume":"39 6","pages":"Pages 903-915"},"PeriodicalIF":3.5,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142186185","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-16DOI: 10.1016/j.ijsrc.2024.08.002
Riham Ezzeldin, Mahmoud Abd-Elmaboud
Dunes formation in sandy rivers significantly impacts flow resistance, subsequently affecting water levels, flow velocity, river navigation, and hydraulic structures performance. Accurate prediction of flow resistance and dune geometry (length and height) is essential for environmental engineering and river management. The current paper introduces two models to evaluate the flow resistance and geometry of dunes formed in sand-bed channels. The first model, RANN–AHA is a hybrid artificial intelligence model using the recurrent artificial neural network (RANN) linked with the artificial hummingbird optimization algorithm (AHA) to optimize the biases and weights of the neural network model. The second model uses gene expression programming (GEP) as a nonlinear approach based on a genetic algorithm (GA) and genetic programming (GP) to explicitly determine dune characteristics. For both models, the input parameters include flow and sediment characteristics, while Manning's roughness coefficient (nM), and relative dune height, h/H or h/L, were used as output parameters where h is the dune height, H is the flow depth above the dune crest, and L is the dune length. Five different published flume data sets were compiled for the analysis. Sensitivity analysis was done using different combinations of input parameters. It was found that the combination of hydraulic radius divided by median diameter (RH/d50), Reynolds number (Re), Particle densimetric Froude number (F∗), and grain Froude number (FG) yielded the best prediction accuracy for estimating Manning nM and relative height, h/H or h/L, with a root mean square error (RMSE) = 0.00027, 0.0504, and 0.0078 and a correlation coefficient (R) = 0.9989, 0.942, and 0.9272, respectively. Model verification proved that the RANN–AHA model outperformed the GEP model and most of the previous studies available in the literature when predicting the roughness coefficient and dune geometry in sand bed channels.
{"title":"Modeling flow resistance and geometry of dunes bed form in alluvial channels using hybrid RANN–AHA and GEP models","authors":"Riham Ezzeldin, Mahmoud Abd-Elmaboud","doi":"10.1016/j.ijsrc.2024.08.002","DOIUrl":"10.1016/j.ijsrc.2024.08.002","url":null,"abstract":"<div><div>Dunes formation in sandy rivers significantly impacts flow resistance, subsequently affecting water levels, flow velocity, river navigation, and hydraulic structures performance. Accurate prediction of flow resistance and dune geometry (length and height) is essential for environmental engineering and river management. The current paper introduces two models to evaluate the flow resistance and geometry of dunes formed in sand-bed channels. The first model, RANN–AHA is a hybrid artificial intelligence model using the recurrent artificial neural network (RANN) linked with the artificial hummingbird optimization algorithm (AHA) to optimize the biases and weights of the neural network model. The second model uses gene expression programming (GEP) as a nonlinear approach based on a genetic algorithm (GA) and genetic programming (GP) to explicitly determine dune characteristics. For both models, the input parameters include flow and sediment characteristics, while Manning's roughness coefficient (<em>n</em><sub>M</sub>), and relative dune height, <em>h</em>/<em>H</em> or <em>h</em>/<em>L</em>, were used as output parameters where <em>h</em> is the dune height, <em>H</em> is the flow depth above the dune crest, and <em>L</em> is the dune length. Five different published flume data sets were compiled for the analysis. Sensitivity analysis was done using different combinations of input parameters. It was found that the combination of hydraulic radius divided by median diameter (<em>R</em><sub>H</sub>/<em>d</em><sub>50</sub>), Reynolds number (Re), Particle densimetric Froude number (<em>F</em>∗), and grain Froude number (<em>F</em><sub>G</sub>) yielded the best prediction accuracy for estimating Manning <em>n</em><sub>M</sub> and relative height, <em>h</em>/<em>H</em> or <em>h</em>/<em>L</em>, with a root mean square error (RMSE) = 0.00027, 0.0504, and 0.0078 and a correlation coefficient (<em>R</em>) = 0.9989, 0.942, and 0.9272, respectively. Model verification proved that the RANN–AHA model outperformed the GEP model and most of the previous studies available in the literature when predicting the roughness coefficient and dune geometry in sand bed channels.</div></div>","PeriodicalId":50290,"journal":{"name":"International Journal of Sediment Research","volume":"39 6","pages":"Pages 885-902"},"PeriodicalIF":3.5,"publicationDate":"2024-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142186089","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-10DOI: 10.1016/j.ijsrc.2024.08.001
Afef Marghmi , Lilia Ben Cheikha , Amina Mabrouk El Asmi , Moncef Gueddari
Water erosion in Tunisian semi-arid regions causes harmful effects by silting reservoirs and reducing agricultural lands and soil fertility. Several factors are involved in the erosion process: rain erosivity, soil fragility, and degraded land cover on steep slopes associated with the intensification of inappropriate human practices. Thus, identifying erosion vulnerable sub-watersheds based on the assessed soil loss rate is very important to apply suitable conservation measures. The current research aimed to prioritize risky areas in the Lakhmess watershed, north-west Tunisia via the Soil Erosion Assessment using Geographical Information System (SEAGIS) model. To prioritize sub-watersheds vulnerable to soil erosion and sediment yield, the Lakhmess watershed, covering an area of 162 km2, was divided into 16 sub-watersheds (L1–L16), according to the hydrographic network. Then, the mean annual soil erosion rate and the mean annual sediment yield in the watershed were estimated by integrating the Revised Universal Soil Loss Equation (RUSLE) and the Sediment Delivery Ratio (SDR) in the SEAGIS model and their spatial distribution was determined. The obtained results indicate that the estimated average annual soil erosion rate is 4.2 t/ha/y and the annual sediment yield is 2.6 t/ha/y. Maner's SDR model was selected as the best model for estimating SY, with standard error, standard deviation, and coefficient of variation values of 0.75%, 0.01, and 0.45%, respectively. The prioritization of the Lakhmess sub-watersheds based on the estimated soil loss rate reveals that among the 16 sub-watersheds, three sub-watersheds (L10, L12, and L15) were identified as being in a very high priority soil erosion class. The high soil erosion rate and sediment yield in these sub-watersheds is explained by the steep slope and a high rainfall erosivity factor. Six sub-watersheds (L2, L4, L5, L6, L7, and L16) were found to belong to a very low priority soil erosion class, as they are characterized by a very gentle slope, which appears to be an extremely determining factor. These findings constitute a basis for decision makers to plan effective conservation measures to conserve agricultural lands, soil, and water resources in northwestern Tunisia.
{"title":"Soil erosion risk assessment of the Lakhmess watershed (northwestern Tunisia) via the SEAGIS model: Inferred prioritization of risky sub-watersheds","authors":"Afef Marghmi , Lilia Ben Cheikha , Amina Mabrouk El Asmi , Moncef Gueddari","doi":"10.1016/j.ijsrc.2024.08.001","DOIUrl":"10.1016/j.ijsrc.2024.08.001","url":null,"abstract":"<div><div>Water erosion in Tunisian semi-arid regions causes harmful effects by silting reservoirs and reducing agricultural lands and soil fertility. Several factors are involved in the erosion process: rain erosivity, soil fragility, and degraded land cover on steep slopes associated with the intensification of inappropriate human practices. Thus, identifying erosion vulnerable sub-watersheds based on the assessed soil loss rate is very important to apply suitable conservation measures. The current research aimed to prioritize risky areas in the Lakhmess watershed, north-west Tunisia via the Soil Erosion Assessment using Geographical Information System (SEAGIS) model. To prioritize sub-watersheds vulnerable to soil erosion and sediment yield, the Lakhmess watershed, covering an area of 162 km<sup>2</sup>, was divided into 16 sub-watersheds (L1–L16), according to the hydrographic network. Then, the mean annual soil erosion rate and the mean annual sediment yield in the watershed were estimated by integrating the Revised Universal Soil Loss Equation (RUSLE) and the Sediment Delivery Ratio (SDR) in the SEAGIS model and their spatial distribution was determined. The obtained results indicate that the estimated average annual soil erosion rate is 4.2 t/ha/y and the annual sediment yield is 2.6 t/ha/y. Maner's SDR model was selected as the best model for estimating SY, with standard error, standard deviation, and coefficient of variation values of 0.75%, 0.01, and 0.45%, respectively. The prioritization of the Lakhmess sub-watersheds based on the estimated soil loss rate reveals that among the 16 sub-watersheds, three sub-watersheds (L10, L12, and L15) were identified as being in a very high priority soil erosion class. The high soil erosion rate and sediment yield in these sub-watersheds is explained by the steep slope and a high rainfall erosivity factor. Six sub-watersheds (L2, L4, L5, L6, L7, and L16) were found to belong to a very low priority soil erosion class, as they are characterized by a very gentle slope, which appears to be an extremely determining factor. These findings constitute a basis for decision makers to plan effective conservation measures to conserve agricultural lands, soil, and water resources in northwestern Tunisia.</div></div>","PeriodicalId":50290,"journal":{"name":"International Journal of Sediment Research","volume":"39 6","pages":"Pages 868-884"},"PeriodicalIF":3.5,"publicationDate":"2024-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142186087","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-01DOI: 10.1016/j.ijsrc.2024.05.003
Lateral intakes are very important for diverting a portion of the river flow and providing the proper flow depth. In cases where small dams are used to operate and control the river's water level for the intake and to meet downstream water needs, the opening and closing of the dam gates before the construction of the intake and during its operation are important. In the current study, the problem of reducing the water head in the intake basin of the Hemmat dam pumping station, especially in the seasons of low water and the accumulation of sediment in the intake inlet of the Hemmat dam located in the Khuzestan province of Iran, has been investigated. Focusing on different arrangements of opening and closing gates, using a spur dike and flow rates of 143, 100, 62, 32, and 12 m3/s to investigate velocity changes and the depth of flow at the water inlet, computational fluid dynamics (CFD) simulations were done. With the spur dike, the water intake efficiency is increased by 384% compared to the project's current state (operation without any flow control structure), and the hydraulic conditions resulting in sedimentation are eliminated. The flow depth of the water intake channel, with the spur dike, increases by 10% compared to the condition without it. It is worth mentioning that gate management also affects water supply efficiency. The results of the current study are a good example of the successful application of computer simulations for sustainable systems engineering.
{"title":"Sustainable systems engineering by CFD modeling of lateral intake flow with flexible gate operations to improve efficient water supply","authors":"","doi":"10.1016/j.ijsrc.2024.05.003","DOIUrl":"10.1016/j.ijsrc.2024.05.003","url":null,"abstract":"<div><p>Lateral intakes are very important for diverting a portion of the river flow and providing the proper flow depth. In cases where small dams are used to operate and control the river's water level for the intake and to meet downstream water needs, the opening and closing of the dam gates before the construction of the intake and during its operation are important. In the current study, the problem of reducing the water head in the intake basin of the Hemmat dam pumping station, especially in the seasons of low water and the accumulation of sediment in the intake inlet of the Hemmat dam located in the Khuzestan province of Iran, has been investigated. Focusing on different arrangements of opening and closing gates, using a spur dike and flow rates of 143, 100, 62, 32, and 12 m<sup>3</sup>/s to investigate velocity changes and the depth of flow at the water inlet, computational fluid dynamics (CFD) simulations were done. With the spur dike, the water intake efficiency is increased by 384% compared to the project's current state (operation without any flow control structure), and the hydraulic conditions resulting in sedimentation are eliminated. The flow depth of the water intake channel, with the spur dike, increases by 10% compared to the condition without it. It is worth mentioning that gate management also affects water supply efficiency. The results of the current study are a good example of the successful application of computer simulations for sustainable systems engineering.</p></div>","PeriodicalId":50290,"journal":{"name":"International Journal of Sediment Research","volume":"39 4","pages":"Pages 629-642"},"PeriodicalIF":3.5,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1001627924000581/pdfft?md5=a53811c0b5371d00f8b14a2bbbd42b3e&pid=1-s2.0-S1001627924000581-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141252921","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}