Martin Dawson, Angela Gurnell, John Lewin, Mark G. Macklin
Recent river studies in the United Kingdom have observed an increase in riparian vegetation and its potential impact on river channel change and sedimentation. Here, we quantify changes in floodplain and riparian vegetation during the first two decades of the 21st century along reaches of eight gravel-bed rivers in England and Wales that exhibit varied active and stable, single and multi-thread planforms. The analysis employs information drawn from open-access sources including national LiDAR surveys and the photographic analysis of repeat aerial and satellite imagery. Most reaches show an increase in woody vegetation across their floodplains reflecting both natural colonisation and deliberate planting, and all but one of the reaches show an increase in woody riparian vegetation cover along their riverbanks. Of the six reaches that have exposed riverine sediments, five show a reduction in exposed sediment area as a result of vegetation encroachment. Contrasts in the rate, extent and location of riparian change were associated with the stability of the channel planform, with differences seen between stable and more active reaches. The significance of riparian woodland in promoting riverbank stability is demonstrated. Riparian vegetation development varies between river reaches, largely in response to differing rates of channel movement but also because of multiple and diverse local decisions regarding the management of in-channel and channel-adjacent vegetation by landowners rather than a single national policy. We consider the relevance of our findings and the value of remote monitoring for future river management interventions.
{"title":"Recent changes in riparian and floodplain vegetation in England and Wales and its geomorphic implications","authors":"Martin Dawson, Angela Gurnell, John Lewin, Mark G. Macklin","doi":"10.1002/rra.4243","DOIUrl":"https://doi.org/10.1002/rra.4243","url":null,"abstract":"Recent river studies in the United Kingdom have observed an increase in riparian vegetation and its potential impact on river channel change and sedimentation. Here, we quantify changes in floodplain and riparian vegetation during the first two decades of the 21st century along reaches of eight gravel-bed rivers in England and Wales that exhibit varied active and stable, single and multi-thread planforms. The analysis employs information drawn from open-access sources including national LiDAR surveys and the photographic analysis of repeat aerial and satellite imagery. Most reaches show an increase in woody vegetation across their floodplains reflecting both natural colonisation and deliberate planting, and all but one of the reaches show an increase in woody riparian vegetation cover along their riverbanks. Of the six reaches that have exposed riverine sediments, five show a reduction in exposed sediment area as a result of vegetation encroachment. Contrasts in the rate, extent and location of riparian change were associated with the stability of the channel planform, with differences seen between stable and more active reaches. The significance of riparian woodland in promoting riverbank stability is demonstrated. Riparian vegetation development varies between river reaches, largely in response to differing rates of channel movement but also because of multiple and diverse local decisions regarding the management of in-channel and channel-adjacent vegetation by landowners rather than a single national policy. We consider the relevance of our findings and the value of remote monitoring for future river management interventions.","PeriodicalId":21513,"journal":{"name":"River Research and Applications","volume":"31 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139664293","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The anomalous variation in the diversion of flow and sediment at the major bifurcation nodes of the Pearl River network in recent years has been generally recognised and accepted, yet the underlying mechanisms have not been revealed. In this study, a large-scale two-dimensional flow-sediment numerical model of the Pearl River estuary was constructed using the TELEMAC-MASCARET modelling system. Additionally, synchronous field surveys from the dry season of 2016 and wet season of 2017 were used to validate the model. The complex branches system of the Pearl River network was generalised. The theoretical models for calculating the water diversion ratio (WDR) of complex estuarine river networks were proposed. The WDR at each river network node is related to Manning's roughness coefficient, the average cross-sectional water depth, the water surface slope, the length of the branches and the average cross-sectional area from the river network nodes to the main estuary outlets. Specifically, the average cross-sectional water depth is the main driver of the formation of the WDRs at the nodes in the Pearl River network. The sediment SDRs at the primary and secondary lateral branching nodes are significantly higher than the WDRs in the dry season, which explains the uneven distribution of flow and sediment. Sediment mining and reclamation are the main factors that have affected the variation in flow and SDRs in the Pearl River network over recent decades.
{"title":"Study on the mechanism of the diversion of flow and sediment in the complex Estuarine River network","authors":"Haoyan Dong, Zixiao He, Liangwen Jia","doi":"10.1002/rra.4247","DOIUrl":"https://doi.org/10.1002/rra.4247","url":null,"abstract":"The anomalous variation in the diversion of flow and sediment at the major bifurcation nodes of the Pearl River network in recent years has been generally recognised and accepted, yet the underlying mechanisms have not been revealed. In this study, a large-scale two-dimensional flow-sediment numerical model of the Pearl River estuary was constructed using the TELEMAC-MASCARET modelling system. Additionally, synchronous field surveys from the dry season of 2016 and wet season of 2017 were used to validate the model. The complex branches system of the Pearl River network was generalised. The theoretical models for calculating the water diversion ratio (WDR) of complex estuarine river networks were proposed. The WDR at each river network node is related to Manning's roughness coefficient, the average cross-sectional water depth, the water surface slope, the length of the branches and the average cross-sectional area from the river network nodes to the main estuary outlets. Specifically, the average cross-sectional water depth is the main driver of the formation of the WDRs at the nodes in the Pearl River network. The sediment SDRs at the primary and secondary lateral branching nodes are significantly higher than the WDRs in the dry season, which explains the uneven distribution of flow and sediment. Sediment mining and reclamation are the main factors that have affected the variation in flow and SDRs in the Pearl River network over recent decades.","PeriodicalId":21513,"journal":{"name":"River Research and Applications","volume":"12 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139664547","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The construction of ecological spur dikes and deep pool shoals can increase the diversity of water flow structures while also hastening the transport and transformation of pollutants. However, current research has paid little attention to the effects of the arrangement parameters on water purification capacity when the ecological spur dikes and deep pool shoals are combined. In this study, we investigated the purification capacity of ammonia nitrogen using the combination of spur dikes and deep pool shoals through laboratory flume experiments and numerical simulation. The laboratory flume experiments revealed that the combination of staggered spur dikes and the opposite side deep pool shoals provided the most effective purification. Secondly, in order to obtain the optimal arrangement parameters for the combination of ecological spur dikes and deep pool shoals more easily, the numerical model based on MIKE21 was validated using experimental results and applied to Section 2 of the Shiqiao River in Nanling County, Wuhu City, Anhui Province. The numerical simulation showed that the length of the spur dikes had the greatest impact on the purification effect, followed by the spacing of the spur dikes and the width of the deep pool shoals, the angle of the spur dikes, the spacing of the deep pool shoals, and the length of the deep pool shoals had the least effect. The optimal parameters for the combination of spur dikes and deep pool shoals are as follows: spur dike parameters: 60°(angle), 10 m(length), 17 m(spacing); deep pool shoal parameters: 60 m(length), 10 m(width), and 210 m(spacing).
{"title":"Study on purification effect of river ammonia nitrogen and optimization of layout parameters in the combination of ecological spur dikes and deep pool shoals: Experiments and MIKE21","authors":"Qihang Wang, Songmin Li, Xiaoling Wang, Yitian Chen, Yazhi Zheng, Guangyao Dong","doi":"10.1002/rra.4246","DOIUrl":"https://doi.org/10.1002/rra.4246","url":null,"abstract":"The construction of ecological spur dikes and deep pool shoals can increase the diversity of water flow structures while also hastening the transport and transformation of pollutants. However, current research has paid little attention to the effects of the arrangement parameters on water purification capacity when the ecological spur dikes and deep pool shoals are combined. In this study, we investigated the purification capacity of ammonia nitrogen using the combination of spur dikes and deep pool shoals through laboratory flume experiments and numerical simulation. The laboratory flume experiments revealed that the combination of staggered spur dikes and the opposite side deep pool shoals provided the most effective purification. Secondly, in order to obtain the optimal arrangement parameters for the combination of ecological spur dikes and deep pool shoals more easily, the numerical model based on MIKE21 was validated using experimental results and applied to Section 2 of the Shiqiao River in Nanling County, Wuhu City, Anhui Province. The numerical simulation showed that the length of the spur dikes had the greatest impact on the purification effect, followed by the spacing of the spur dikes and the width of the deep pool shoals, the angle of the spur dikes, the spacing of the deep pool shoals, and the length of the deep pool shoals had the least effect. The optimal parameters for the combination of spur dikes and deep pool shoals are as follows: spur dike parameters: 60°(angle), 10 m(length), 17 m(spacing); deep pool shoal parameters: 60 m(length), 10 m(width), and 210 m(spacing).","PeriodicalId":21513,"journal":{"name":"River Research and Applications","volume":"227 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139645525","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chun-ying Shen, Yu-bin Chen, Xiao-tao Shi, Ming-ming Wang, Shi-hua He
The three-dimensional flow velocities within the typical pool chamber of the rectangular fishway were measured in a vertical slit bottom-hole combination fishway by a hydraulic model test using an acoustic Doppler velocimeter (ADV). This was aimed to analyze the effect of eddy structures within the pool chamber of the fishway on fish migration. Based on this, a numerical simulation study was conducted using the Reynolds mean model (RNG k-ε) and large eddy simulation (LES). Additionally, the omega (Ω) eddy identification method was used to identify the eddy structure within the pool chamber of the fishway and dissect the flow characteristics of the water body within the pool chamber. The findings revealed that longitudinal flow velocity dominated the flow in the lower bottom layer of the pond. Moreover, the flow in the middle and upper layers was more turbulent and there is a phenomenon of backflow upstream, and the flow at the orifice was a divergent jet with the main flow slightly to the right bank, forming two vortices in opposite directions on both sides of the orifice. The fish passage mainly displayed the turbulent vortex structure, which can effectively slow down the water flow and provide a resting place for migratory fish. The vortex identification method can more accurately identify the vortex structure inside the flow field.
{"title":"Turbulent structural analysis of the combined fishway with vertical seam and bottom hole","authors":"Chun-ying Shen, Yu-bin Chen, Xiao-tao Shi, Ming-ming Wang, Shi-hua He","doi":"10.1002/rra.4244","DOIUrl":"https://doi.org/10.1002/rra.4244","url":null,"abstract":"The three-dimensional flow velocities within the typical pool chamber of the rectangular fishway were measured in a vertical slit bottom-hole combination fishway by a hydraulic model test using an acoustic Doppler velocimeter (ADV). This was aimed to analyze the effect of eddy structures within the pool chamber of the fishway on fish migration. Based on this, a numerical simulation study was conducted using the Reynolds mean model (RNG <i>k-ε</i>) and large eddy simulation (LES). Additionally, the omega (<i>Ω</i>) eddy identification method was used to identify the eddy structure within the pool chamber of the fishway and dissect the flow characteristics of the water body within the pool chamber. The findings revealed that longitudinal flow velocity dominated the flow in the lower bottom layer of the pond. Moreover, the flow in the middle and upper layers was more turbulent and there is a phenomenon of backflow upstream, and the flow at the orifice was a divergent jet with the main flow slightly to the right bank, forming two vortices in opposite directions on both sides of the orifice. The fish passage mainly displayed the turbulent vortex structure, which can effectively slow down the water flow and provide a resting place for migratory fish. The vortex identification method can more accurately identify the vortex structure inside the flow field.","PeriodicalId":21513,"journal":{"name":"River Research and Applications","volume":"87 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139645377","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Leif Kastdalen, Morten Stickler, Christian Malmquist, Jan Heggenes
The objective was to evaluate the feasibility of measuring bathymetry using airborne green LiDAR in long and variable river reaches (4 km or more), across three rivers with varying gradients, water depths and light penetration (3.5–10 m), using four alternative LiDAR sensors. The accuracy of green LiDAR data was compared to in situ measurements collected by stratified transect point sampling and Multibeam bathymetry. Factors potentially limiting the feasibility of green LIDAR in rivers were explored. If remote sensing signals were reflected by the riverbed, the sensors generally provided elevation data consistent with in situ elevation measurements, indicating high accuracy (±10 cm) across different hydraulic conditions. The loss of green LiDAR data was mainly a consequence of limited signal water penetration capability, that is, water clarity. Secchi depth was a proxy variable strongly associated with green LiDAR penetration capability across rivers. Data loss was low up to the Secchi depth but increased rapidly thereafter. Surface water turbulence (‘white water’) and dark riverbed vegetation also increased green LiDAR signal loss. Sensors with lower point density and therefore less spatial resolution had more signal strength and therefore penetrated deeper water. However, with increasing coverage of surface turbulence (‘white water’), the importance of high point density also increased. Signal power should be balanced with signal density (spatial resolution), depending on river characteristics and project objectives. We conclude that remote sensing green LiDAR bathymetry is a robust method that efficiently provides accurate elevation data across rivers with different hydraulic conditions and water depths.
{"title":"Evaluating methods for measuring in-river bathymetry: Remote sensing green LIDAR provides high-resolution channel bed topography limited by water penetration capability","authors":"Leif Kastdalen, Morten Stickler, Christian Malmquist, Jan Heggenes","doi":"10.1002/rra.4245","DOIUrl":"https://doi.org/10.1002/rra.4245","url":null,"abstract":"The objective was to evaluate the feasibility of measuring bathymetry using airborne green LiDAR in long and variable river reaches (4 km or more), across three rivers with varying gradients, water depths and light penetration (3.5–10 m), using four alternative LiDAR sensors. The accuracy of green LiDAR data was compared to in situ measurements collected by stratified transect point sampling and Multibeam bathymetry. Factors potentially limiting the feasibility of green LIDAR in rivers were explored. If remote sensing signals were reflected by the riverbed, the sensors generally provided elevation data consistent with in situ elevation measurements, indicating high accuracy (±10 cm) across different hydraulic conditions. The loss of green LiDAR data was mainly a consequence of limited signal water penetration capability, that is, water clarity. Secchi depth was a proxy variable strongly associated with green LiDAR penetration capability across rivers. Data loss was low up to the Secchi depth but increased rapidly thereafter. Surface water turbulence (‘white water’) and dark riverbed vegetation also increased green LiDAR signal loss. Sensors with lower point density and therefore less spatial resolution had more signal strength and therefore penetrated deeper water. However, with increasing coverage of surface turbulence (‘white water’), the importance of high point density also increased. Signal power should be balanced with signal density (spatial resolution), depending on river characteristics and project objectives. We conclude that remote sensing green LiDAR bathymetry is a robust method that efficiently provides accurate elevation data across rivers with different hydraulic conditions and water depths.","PeriodicalId":21513,"journal":{"name":"River Research and Applications","volume":"293 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139578269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Anna Marshall, Ryan R. Morrison, Brady Jones, Shayla Triantafillou, Ellen Wohl
Wood accumulations influence geomorphic, hydraulic, and ecologic functions within a river corridor, but characterizing these accumulations presents challenges across a range of field and remote sensing methodologies. We evaluate the ability of handheld lidar scanners, specifically lidar-scanning capabilities of a fourth-generation iPad Pro, to collect three-dimensional wood accumulation data, which can be used to inform measurements of wood volume, porosity, complexity, and roughness. We discuss the potential and limitations of this novel methodology for river research and management. We found that handheld lidar presents a cost-effective input for data-processing workflows that field measurements of wood accumulation dimensions cannot as easily replicate including (1) a user-friendly means of data collection and visualization; (2) accurate comparisons of wood volume over time; (3) integration into workflows to measure porosity parameters; and (4) potential use in informing hydraulic and morphodynamic models. Consideration of study area constraints and intended use of scans are prerequisites to using handheld lidar as an effective tool. We identified some specific limitations of using handheld lidar scanners in wood-rich river corridors, including (1) scanners perform poorly when wood is under water or surrounded by dense vegetation; (2) scanners require physical access to areas of interest at distances less than 5 m; (3) scans need to be manually georeferenced; and (4) scans require manual measurements for any dimensional data, which still have associated user time and error. Handheld lidar as a scientific tool is rapidly developing and there is substantial room for expansion of applications, utilization, and advances in the use of this tool in river research and management.
木材堆积会影响河流走廊内的地貌、水力和生态功能，但要描述这些堆积物的特征却给一系列野外和遥感方法带来了挑战。我们评估了手持式激光雷达扫描仪（特别是第四代 iPad Pro 的激光雷达扫描功能）收集三维木材堆积数据的能力，这些数据可用来为木材体积、孔隙度、复杂性和粗糙度的测量提供信息。我们讨论了这种新方法在河流研究和管理方面的潜力和局限性。我们发现，手持激光雷达为数据处理工作流程提供了一种具有成本效益的输入，而对木材堆积尺寸的实地测量则无法轻易复制，其中包括：（1）用户友好的数据收集和可视化手段；（2）随时间变化的木材体积的精确比较；（3）集成到工作流程中以测量孔隙度参数；以及（4）在为水力和形态动力学模型提供信息方面的潜在用途。将手持激光雷达用作有效工具的前提条件是考虑到研究区域的限制和扫描的预期用途。我们发现了在木材丰富的河流走廊使用手持式激光雷达扫描仪的一些具体局限性，其中包括：（1）当木材处于水下或被茂密植被包围时，扫描仪的性能较差；（2）扫描仪需要实际进入距离小于 5 米的感兴趣区域；（3）扫描需要手动进行地理坐标参考；以及（4）扫描需要手动测量任何尺寸数据，这仍然会产生相关的用户时间和误差。作为一种科学工具，手持式激光雷达正在迅速发展，在河流研究和管理中，这种工具的应用、利用和进步还有很大的扩展空间。
{"title":"Handheld lidar as a tool for characterizing wood-rich river corridors","authors":"Anna Marshall, Ryan R. Morrison, Brady Jones, Shayla Triantafillou, Ellen Wohl","doi":"10.1002/rra.4239","DOIUrl":"https://doi.org/10.1002/rra.4239","url":null,"abstract":"Wood accumulations influence geomorphic, hydraulic, and ecologic functions within a river corridor, but characterizing these accumulations presents challenges across a range of field and remote sensing methodologies. We evaluate the ability of handheld lidar scanners, specifically lidar-scanning capabilities of a fourth-generation iPad Pro, to collect three-dimensional wood accumulation data, which can be used to inform measurements of wood volume, porosity, complexity, and roughness. We discuss the potential and limitations of this novel methodology for river research and management. We found that handheld lidar presents a cost-effective input for data-processing workflows that field measurements of wood accumulation dimensions cannot as easily replicate including (1) a user-friendly means of data collection and visualization; (2) accurate comparisons of wood volume over time; (3) integration into workflows to measure porosity parameters; and (4) potential use in informing hydraulic and morphodynamic models. Consideration of study area constraints and intended use of scans are prerequisites to using handheld lidar as an effective tool. We identified some specific limitations of using handheld lidar scanners in wood-rich river corridors, including (1) scanners perform poorly when wood is under water or surrounded by dense vegetation; (2) scanners require physical access to areas of interest at distances less than 5 m; (3) scans need to be manually georeferenced; and (4) scans require manual measurements for any dimensional data, which still have associated user time and error. Handheld lidar as a scientific tool is rapidly developing and there is substantial room for expansion of applications, utilization, and advances in the use of this tool in river research and management.","PeriodicalId":21513,"journal":{"name":"River Research and Applications","volume":"17 7","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139552256","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Borbála Hortobágyi, Stéphane Petit, Baptiste Marteau, Gabriel Melun, Hervé Piégay
Rivers with alluvial bars store more wood than those without, supplied through channel shifting. However, wood dynamics (arrival or new deposits, departure or entrainment, and stable or immobile pieces) can vary substantially over time in response to critical hydrological drivers that are largely unknown. To evaluate them, we studied the dynamics of large wood pieces and logjams along a 12-km reach of the lower Allier River using six series of aerial images of variable resolution acquired between 2009 and 2020, during which maximum river discharge fluctuated around the dominant flood discharge (Q1.5) that is potentially the bankfull discharge along this well-preserved not incised reach. Individual wood departure was best correlated with water levels exceeding dominant flood discharge. The duration of the highest magnitude flood was best correlated with wood depositions, with shorter floods resulting in a higher number of deposits. Finally, most of the wood remained stable when river discharge did not exceed 60% of Q1.5 over a long period of time. Changes in inter-annual wood budget (reach-scale) depend on the duration over which discharge exceeded 60% of Q1.5. Hydrological conditions driving jam build-up and removal were similar to those controlling individual wood piece dynamics. The results suggest that specific hydrological conditions influence the dynamics of large wood and log jams in the Allier River. Understanding the dynamics of large wood and its impact on river morphology is fundamental for successful river management and habitat restoration initiatives.
{"title":"A high-resolution inter-annual framework for exploring hydrological drivers of large wood dynamics","authors":"Borbála Hortobágyi, Stéphane Petit, Baptiste Marteau, Gabriel Melun, Hervé Piégay","doi":"10.1002/rra.4242","DOIUrl":"https://doi.org/10.1002/rra.4242","url":null,"abstract":"Rivers with alluvial bars store more wood than those without, supplied through channel shifting. However, wood dynamics (arrival or new deposits, departure or entrainment, and stable or immobile pieces) can vary substantially over time in response to critical hydrological drivers that are largely unknown. To evaluate them, we studied the dynamics of large wood pieces and logjams along a 12-km reach of the lower Allier River using six series of aerial images of variable resolution acquired between 2009 and 2020, during which maximum river discharge fluctuated around the dominant flood discharge (Q<sub>1.5</sub>) that is potentially the bankfull discharge along this well-preserved not incised reach. Individual wood departure was best correlated with water levels exceeding dominant flood discharge. The duration of the highest magnitude flood was best correlated with wood depositions, with shorter floods resulting in a higher number of deposits. Finally, most of the wood remained stable when river discharge did not exceed 60% of Q<sub>1.5</sub> over a long period of time. Changes in inter-annual wood budget (reach-scale) depend on the duration over which discharge exceeded 60% of Q<sub>1.5</sub>. Hydrological conditions driving jam build-up and removal were similar to those controlling individual wood piece dynamics. The results suggest that specific hydrological conditions influence the dynamics of large wood and log jams in the Allier River. Understanding the dynamics of large wood and its impact on river morphology is fundamental for successful river management and habitat restoration initiatives.","PeriodicalId":21513,"journal":{"name":"River Research and Applications","volume":"214 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139551843","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mojgan Zare Shahraki, Pejman Fathi, Eisa Ebrahimi Dorche, Joseph Flotemersch, Karen Blocksom, James Stribling, Andreas Bruder
The tolerance of aquatic organisms to stressors is widely used to monitor and evaluate the condition of freshwater ecosystems. Tolerance values (TV) derived from analyses of the relationship between species and their environment are considered to be more objective than those that rely on expert opinion. We used principal component analysis (PCA) to derive a generalized stressor gradient based on physicochemical characteristics and physical habitat quality and structure. Scores of the first principal component axis (PC1) were used to estimate TV for 37 fish species collected from 54 sites in the Karun River basin, Iran. PCA of 17 variables identified stressors that were influential such as total phosphate, total nitrogen, total coliform, and habitat and morphological score. The species were separated into three categories on the stressor gradient: sensitive (18.9%), semi-tolerant (48.6%), and tolerant species (32.4%). Based on these results we developed the Karun Fish Tolerance Index (KFTI) and demonstrated that it performed well in separating the least, moderate, and most disturbed sites in the study area. The discrimination efficiency of the KFTI was 82.5%, which makes it a robust management tool for the protection and conservation of streams and rivers in the Karun River watershed. TV developed here reflect objective characteristics of the sensitivity of fish species to the predominant stressors in the Karun and similar systems.
水生生物对压力的耐受性被广泛用于监测和评估淡水生态系统的状况。通过分析物种与其环境之间的关系得出的耐受值（TV）被认为比依靠专家意见得出的耐受值更加客观。我们使用主成分分析法（PCA），根据物理化学特征和物理生境质量与结构得出了一个广义的压力梯度。第一主成分轴（PC1）的得分用于估算从伊朗卡伦河流域 54 个地点采集的 37 种鱼类的 TV 值。通过对 17 个变量进行 PCA 分析，确定了总磷酸盐、总氮、总大肠菌群以及栖息地和形态得分等影响因素。根据压力梯度将物种分为三类：敏感物种（18.9%）、半耐受物种（48.6%）和耐受物种（32.4%）。根据这些结果，我们制定了卡伦鱼类耐受指数（Karun Fish Tolerance Index，KFTI），并证明该指数在区分研究区域内受干扰最少、中等和最严重的地点方面表现良好。KFTI 的区分效率为 82.5%，这使其成为保护和养护卡伦河流域溪流和河流的有力管理工具。在此开发的 TV 反映了卡伦河及类似水系中鱼类物种对主要压力因素敏感性的客观特征。
{"title":"Environmental impact assessment and conservation planning of a Middle-Eastern River basin using a fish-based tolerance index","authors":"Mojgan Zare Shahraki, Pejman Fathi, Eisa Ebrahimi Dorche, Joseph Flotemersch, Karen Blocksom, James Stribling, Andreas Bruder","doi":"10.1002/rra.4233","DOIUrl":"https://doi.org/10.1002/rra.4233","url":null,"abstract":"The tolerance of aquatic organisms to stressors is widely used to monitor and evaluate the condition of freshwater ecosystems. Tolerance values (TV) derived from analyses of the relationship between species and their environment are considered to be more objective than those that rely on expert opinion. We used principal component analysis (PCA) to derive a generalized stressor gradient based on physicochemical characteristics and physical habitat quality and structure. Scores of the first principal component axis (PC1) were used to estimate TV for 37 fish species collected from 54 sites in the Karun River basin, Iran. PCA of 17 variables identified stressors that were influential such as total phosphate, total nitrogen, total coliform, and habitat and morphological score. The species were separated into three categories on the stressor gradient: sensitive (18.9%), semi-tolerant (48.6%), and tolerant species (32.4%). Based on these results we developed the Karun Fish Tolerance Index (KFTI) and demonstrated that it performed well in separating the least, moderate, and most disturbed sites in the study area. The discrimination efficiency of the KFTI was 82.5%, which makes it a robust management tool for the protection and conservation of streams and rivers in the Karun River watershed. TV developed here reflect objective characteristics of the sensitivity of fish species to the predominant stressors in the Karun and similar systems.","PeriodicalId":21513,"journal":{"name":"River Research and Applications","volume":"174 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139477023","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Martha L. Villamizar, Chris Stoate, Jeremy Biggs, John Szczur, Penny Williams, Colin D. Brown
Leaky barriers have become an important mitigation option within natural flood management to reduce downstream flood risk. Modelling is a key tool to aid in the design of leaky barrier installations for flood mitigation, but there is limited evidence about the accuracy of model representations of the system. Here, the hydrological model SWAT was combined with a water routing model that simulates multiple leaky barriers as permeable sluice gates. Storage behind individual barriers was quantified using barrier dimensions and LIDAR topography. The model was applied to a series of 27 leaky barriers installed as part of a long-term manipulation experiment into a 11-km2 intensive lowland agricultural catchment in Leicestershire, England. Evaluation of the model against flow data collected before and after leaky barrier installation and time-lapse photography taken across storm events at individual barriers demonstrated robust model performance (Nash-Sutcliffe efficiency and R2 across 19 validation events were 0.84 ± 0.14 and 0.91 ± 0.08, respectively). Empirical and modelling data were then combined to demonstrate that the 17,700 m3 of water storage provided by the 27 leaky barriers reduced peak flows at the catchment outlet by 22 ± 6% and delayed the peak in flow by up to 5 h for 11 storm events recorded after all barriers had been installed. The volume of storage utilised prior to the flood event was a key factor influencing the reduction in peak flow, and a sensitivity analysis indicated that barriers should be permeable to accelerate drain-down of the barrier and help to mitigate risk from multiple storm events occurring in sequence.
{"title":"A model for quantifying the effectiveness of leaky barriers as a flood mitigation intervention in an agricultural landscape","authors":"Martha L. Villamizar, Chris Stoate, Jeremy Biggs, John Szczur, Penny Williams, Colin D. Brown","doi":"10.1002/rra.4241","DOIUrl":"https://doi.org/10.1002/rra.4241","url":null,"abstract":"Leaky barriers have become an important mitigation option within natural flood management to reduce downstream flood risk. Modelling is a key tool to aid in the design of leaky barrier installations for flood mitigation, but there is limited evidence about the accuracy of model representations of the system. Here, the hydrological model SWAT was combined with a water routing model that simulates multiple leaky barriers as permeable sluice gates. Storage behind individual barriers was quantified using barrier dimensions and LIDAR topography. The model was applied to a series of 27 leaky barriers installed as part of a long-term manipulation experiment into a 11-km<sup>2</sup> intensive lowland agricultural catchment in Leicestershire, England. Evaluation of the model against flow data collected before and after leaky barrier installation and time-lapse photography taken across storm events at individual barriers demonstrated robust model performance (Nash-Sutcliffe efficiency and <i>R</i><sup>2</sup> across 19 validation events were 0.84 ± 0.14 and 0.91 ± 0.08, respectively). Empirical and modelling data were then combined to demonstrate that the 17,700 m<sup>3</sup> of water storage provided by the 27 leaky barriers reduced peak flows at the catchment outlet by 22 ± 6% and delayed the peak in flow by up to 5 h for 11 storm events recorded after all barriers had been installed. The volume of storage utilised prior to the flood event was a key factor influencing the reduction in peak flow, and a sensitivity analysis indicated that barriers should be permeable to accelerate drain-down of the barrier and help to mitigate risk from multiple storm events occurring in sequence.","PeriodicalId":21513,"journal":{"name":"River Research and Applications","volume":"13 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139459031","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sagar Dahal, Kaustuv Raj Neupane, Bashu Dev Baral, Simon Poulton
The rate of hydropower dam construction on rivers is increasing in emerging economies in South Asia, to achieve economic development goals. These large infrastructure projects are likely to have many negative consequences on freshwater species but have not yet received much consideration. Among freshwater small mammalian species, water shrews are seriously impacted by these large structures. This paper aims to determine if water shrews have been considered during the Environmental Impact Assessment (EIA) of these hydro dam project sites, as well as present the sightings of the water shrews from Nepalese rivers with hydropower potential. We reviewed 44 EIA reports of such projects in Nepal using a set of four criteria and 15 questions to analyze the methods of impact assessment for mammals and the reports on the presence of water shrews in each built area. The study found that the number of mammal species reported during the EIA varied from five to 55 species but no relationships between the hydropower structure's size and any water shrew species were considered in the studies. In almost all EIA reports, the term aquatic ecosystem was prioritized over the term aquatic small mammals, and the latter was not considered in the assessment. The major reason for not considering these species is probably due to the lack of robust methods to capture small mammals such as shrews, or due to survey methods focused only on terrestrial mammals. The Aquatic Animal Protection Act was fully reviewed and assured to be followed in a majority of the reports, yet the monitoring parameters and indicators were not available for aquatic small mammals. Ignoring the presence of these mammals while constructing hydropower plants is a serious threat to their persistence. We also reported the Himalayan water shrew in the Barun River and the elegant water shrew in the Upper Tamakoshi River of Nepal. Therefore, a better understanding of these species among hydropower developers, and all concerned agencies, is essential.
{"title":"Disregard of aquatic shrews in the Environmental Impact Assessment reports regarding hydropower dams in the Nepal Himalayas","authors":"Sagar Dahal, Kaustuv Raj Neupane, Bashu Dev Baral, Simon Poulton","doi":"10.1002/rra.4238","DOIUrl":"https://doi.org/10.1002/rra.4238","url":null,"abstract":"The rate of hydropower dam construction on rivers is increasing in emerging economies in South Asia, to achieve economic development goals. These large infrastructure projects are likely to have many negative consequences on freshwater species but have not yet received much consideration. Among freshwater small mammalian species, water shrews are seriously impacted by these large structures. This paper aims to determine if water shrews have been considered during the Environmental Impact Assessment (EIA) of these hydro dam project sites, as well as present the sightings of the water shrews from Nepalese rivers with hydropower potential. We reviewed 44 EIA reports of such projects in Nepal using a set of four criteria and 15 questions to analyze the methods of impact assessment for mammals and the reports on the presence of water shrews in each built area. The study found that the number of mammal species reported during the EIA varied from five to 55 species but no relationships between the hydropower structure's size and any water shrew species were considered in the studies. In almost all EIA reports, the term aquatic ecosystem was prioritized over the term aquatic small mammals, and the latter was not considered in the assessment. The major reason for not considering these species is probably due to the lack of robust methods to capture small mammals such as shrews, or due to survey methods focused only on terrestrial mammals. The Aquatic Animal Protection Act was fully reviewed and assured to be followed in a majority of the reports, yet the monitoring parameters and indicators were not available for aquatic small mammals. Ignoring the presence of these mammals while constructing hydropower plants is a serious threat to their persistence. We also reported the Himalayan water shrew in the Barun River and the elegant water shrew in the Upper Tamakoshi River of Nepal. Therefore, a better understanding of these species among hydropower developers, and all concerned agencies, is essential.","PeriodicalId":21513,"journal":{"name":"River Research and Applications","volume":"88 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139459160","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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