Investigations of water flow movements affected by vegetation is a research hotspot in vegetation ecological restoration. The theory and equations of the flow velocity distribution under the influence of rigid vegetation are relatively mature. This study proposes a new drag force equation that varies with the vegetation bending angle and a new analytical solution of the velocity profile. Comparisons between the model calculation and experimental data, results showed that this new proposed model produced accurate simulations for flow through flexible vegetation for various deflections. In addition, this analytical model was verified to be applicable to rigid vegetation without a bending angle. Moreover, the features of the parameters adopted in this analytical equation are discussed, and the empirical equation for these parameters are presented. This study further improves the research in the field of environmental fluid mechanics and can serve as a theoretical underpinning for the ecological restoration of river courses.
{"title":"New Drag Force Formula of Bending Stems in Deriving Analytical Solutions of Velocity Profile for Flow Through Flexible Vegetation","authors":"Jin-Jin Li, Wei-Jie Wang, Fei Dong, Wen-Qi Peng, Jing-Jing Fan, Han-Qing Zhao, Qing-Chuan Chou, Ai-Ping Huang","doi":"10.1029/2023wr035951","DOIUrl":"https://doi.org/10.1029/2023wr035951","url":null,"abstract":"Investigations of water flow movements affected by vegetation is a research hotspot in vegetation ecological restoration. The theory and equations of the flow velocity distribution under the influence of rigid vegetation are relatively mature. This study proposes a new drag force equation that varies with the vegetation bending angle and a new analytical solution of the velocity profile. Comparisons between the model calculation and experimental data, results showed that this new proposed model produced accurate simulations for flow through flexible vegetation for various deflections. In addition, this analytical model was verified to be applicable to rigid vegetation without a bending angle. Moreover, the features of the parameters adopted in this analytical equation are discussed, and the empirical equation for these parameters are presented. This study further improves the research in the field of environmental fluid mechanics and can serve as a theoretical underpinning for the ecological restoration of river courses.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":null,"pages":null},"PeriodicalIF":5.4,"publicationDate":"2024-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141754351","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Carl J. Legleiter, Brandon T. Overstreet, Paul J. Kinzel
Remote sensing can be an effective tool for mapping river bathymetry, but the need for direct measurements to calibrate image-derived depth estimates impedes broader application of this approach. One way to circumvent the need for field campaigns dedicated to calibration is to capitalize upon existing data. In this study, we introduce a framework for Bathymetric Mapping using Gage Records and Image Databases (BaMGRID). This workflow involves retrieving depth measurements made during gaging station site visits, downloading archived multispectral images, and then combining these two data sets to establish a relationship between depth and reflectance. We developed a processing chain that involves using application programming interfaces to obtain both depth measurements made during site visits and images centered on the gage and then linking depth to reflectance via an optimal band ratio analysis (OBRA) algorithm modified for small sample sizes. Applying this workflow to selected gages within two river basins indicated that depth retrieval from multispectral satellite images could be highly accurate, but with variable results from one image to the next at a given site. High resolution aerial photography was less conducive to bathymetric mapping in one of the basin considered. Of the four predictors of depth retrieval performance we evaluated (mean and standard deviation of depth, width, and an index of water clarity), only width was consistently significantly correlated with OBRA R2 (p < 0.026). Currently, BaMGRID is best-suited for site-by-site analysis to support practical applications at the reach scale; continuous, basin-wide mapping of river bathymetry will require additional research.
遥感技术是绘制河流水深测量图的有效工具，但由于需要直接测量来校准由图像得出的深度估计值，因此阻碍了这一方法的更广泛应用。规避专门用于校准的实地测量的方法之一是利用现有数据。在本研究中，我们介绍了一个利用测深记录和图像数据库（BaMGRID）进行测深绘图的框架。该工作流程包括检索在测量站实地考察期间进行的深度测量，下载存档的多光谱图像，然后将这两个数据集结合起来，建立深度与反射率之间的关系。我们开发了一个处理链，包括使用应用程序接口获取实地考察期间的深度测量数据和以测站为中心的图像，然后通过针对小样本量修改的最优波段比分析 (OBRA) 算法将深度与反射率联系起来。将这一工作流程应用于两个流域内的选定水文站表明，从多光谱卫星图像中进行深度检索的准确性很高，但在特定地点，不同图像的结果各不相同。在其中一个流域，高分辨率航空摄影对测深绘图的帮助较小。在我们评估的深度检索性能的四个预测因子（深度的平均值和标准偏差、宽度和水透明度指数）中，只有宽度与 OBRA R2 一直存在显著相关性（p < 0.026）。目前，BaMGRID 最适合用于逐点分析，以支持河段尺度的实际应用；连续、全流域的河流水深测绘还需要更多的研究。
{"title":"Integrating Depth Measurements From Gaging Stations With Image Archives for Spectrally Based Remote Sensing of River Bathymetry","authors":"Carl J. Legleiter, Brandon T. Overstreet, Paul J. Kinzel","doi":"10.1029/2024wr037295","DOIUrl":"https://doi.org/10.1029/2024wr037295","url":null,"abstract":"Remote sensing can be an effective tool for mapping river bathymetry, but the need for direct measurements to calibrate image-derived depth estimates impedes broader application of this approach. One way to circumvent the need for field campaigns dedicated to calibration is to capitalize upon existing data. In this study, we introduce a framework for Bathymetric Mapping using Gage Records and Image Databases (BaMGRID). This workflow involves retrieving depth measurements made during gaging station site visits, downloading archived multispectral images, and then combining these two data sets to establish a relationship between depth and reflectance. We developed a processing chain that involves using application programming interfaces to obtain both depth measurements made during site visits and images centered on the gage and then linking depth to reflectance via an optimal band ratio analysis (OBRA) algorithm modified for small sample sizes. Applying this workflow to selected gages within two river basins indicated that depth retrieval from multispectral satellite images could be highly accurate, but with variable results from one image to the next at a given site. High resolution aerial photography was less conducive to bathymetric mapping in one of the basin considered. Of the four predictors of depth retrieval performance we evaluated (mean and standard deviation of depth, width, and an index of water clarity), only width was consistently significantly correlated with OBRA <i>R</i><sup>2</sup> (<i>p</i> < 0.026). Currently, BaMGRID is best-suited for site-by-site analysis to support practical applications at the reach scale; continuous, basin-wide mapping of river bathymetry will require additional research.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":null,"pages":null},"PeriodicalIF":5.4,"publicationDate":"2024-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141732730","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lateral erosion is a critical factor that influences the formation and amplification of debris flows. However, our understanding of the bank retreat process in debris flow channels is limited, which limits the evaluation of debris flow magnitudes and the prediction of their activity trends. Herein, we conduct physical experiments to investigate bank retreat mechanisms using five types of bank soil and multiple debris flow surges. The bank retreat process is categorized into two stages: toe cutting and bank collapse. Toe cutting is mainly caused by hydraulic erosion, bank collapse includes gravity erosion in the form of toppling failure. Notably, the bank retreat process exhibits a significant negative feedback loop. Bank erosion widens the channel bed, subsequently decreasing the flow depth. In turn, this reduction in flow depth mitigates bank erosion. Moreover, we discover a concise pattern in the complex coupling of hydraulic erosion and toppling failure: erosion efficiency is linearly and negatively correlated with the bed widening width. We develop a new parameterized model for describing the bank retreat process and provided empirical values for the model parameters. Furthermore, we observe that the initial erosion efficiency first increases and then decreases with an increase in the fine particle content of the bank soil. Additionally, we report a negative correlation between the maximum bed widening width and the fine particle content in the bank soil that follows a power function relationship.
{"title":"Bank Retreat Mechanisms Driven by Debris Flow Surges: A Parameterized Model Based on the Results of Physical Experiments","authors":"Xi'an Wang, Jiangang Chen, Xiaoqing Chen, Huayong Chen, Wanyu Zhao, Hechun Ruan, Jinshui Wang","doi":"10.1029/2023wr036914","DOIUrl":"https://doi.org/10.1029/2023wr036914","url":null,"abstract":"Lateral erosion is a critical factor that influences the formation and amplification of debris flows. However, our understanding of the bank retreat process in debris flow channels is limited, which limits the evaluation of debris flow magnitudes and the prediction of their activity trends. Herein, we conduct physical experiments to investigate bank retreat mechanisms using five types of bank soil and multiple debris flow surges. The bank retreat process is categorized into two stages: toe cutting and bank collapse. Toe cutting is mainly caused by hydraulic erosion, bank collapse includes gravity erosion in the form of toppling failure. Notably, the bank retreat process exhibits a significant negative feedback loop. Bank erosion widens the channel bed, subsequently decreasing the flow depth. In turn, this reduction in flow depth mitigates bank erosion. Moreover, we discover a concise pattern in the complex coupling of hydraulic erosion and toppling failure: erosion efficiency is linearly and negatively correlated with the bed widening width. We develop a new parameterized model for describing the bank retreat process and provided empirical values for the model parameters. Furthermore, we observe that the initial erosion efficiency first increases and then decreases with an increase in the fine particle content of the bank soil. Additionally, we report a negative correlation between the maximum bed widening width and the fine particle content in the bank soil that follows a power function relationship.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":null,"pages":null},"PeriodicalIF":5.4,"publicationDate":"2024-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141746579","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nisreen G. Al-Ghorani, Marwan A. Hassan, Conor McDowell
This study examines the spatial pattern of fractional sediment mobility and assesses the influence of morphologic units on bedload transport in a small pool-riffle reach with limited supply. Using a 2D hydraulic model and a subsurface-based sediment transport model, shear stresses, fractional sediment mobility, and bedload transport were examined for flow events ranging in magnitude between 0.2Qbf and 1.5Qbf. Results reveal that while spatial variations in shear stress decrease as discharge increases, only a small proportion of the bed experiences high transport rates. At the reach scale, riffles are the primary morphological unit contributing to fully mobile sediment for all size fractions. However, at a subunit scale, there is evidence of sediment transport reversal for grains >32 mm at flows near or exceeding bankfull discharge in association with shear stress reversal. These transport reversals are important for maintaining pools despite their infrequent occurrence in the study reach. Sediment transport maps indicate that bed morphology considerably influences sediment transport at low to moderate flows. During these events, the shear stress is sensitive to local bed topography and partial mobility is the dominant transport process. In contrast, variations in bedload transport rates decrease during high flows when the flow is less sensitive to variations in bed topography and the bed becomes fully mobile.
{"title":"Evaluating the Effect of Morphologic Units on Fractional Sediment Mobility and Bedload Transport in a Small Pool-Riffle Reach","authors":"Nisreen G. Al-Ghorani, Marwan A. Hassan, Conor McDowell","doi":"10.1029/2024wr037348","DOIUrl":"https://doi.org/10.1029/2024wr037348","url":null,"abstract":"This study examines the spatial pattern of fractional sediment mobility and assesses the influence of morphologic units on bedload transport in a small pool-riffle reach with limited supply. Using a 2D hydraulic model and a subsurface-based sediment transport model, shear stresses, fractional sediment mobility, and bedload transport were examined for flow events ranging in magnitude between 0.2Q<sub>bf</sub> and 1.5Q<sub>bf</sub>. Results reveal that while spatial variations in shear stress decrease as discharge increases, only a small proportion of the bed experiences high transport rates. At the reach scale, riffles are the primary morphological unit contributing to fully mobile sediment for all size fractions. However, at a subunit scale, there is evidence of sediment transport reversal for grains >32 mm at flows near or exceeding bankfull discharge in association with shear stress reversal. These transport reversals are important for maintaining pools despite their infrequent occurrence in the study reach. Sediment transport maps indicate that bed morphology considerably influences sediment transport at low to moderate flows. During these events, the shear stress is sensitive to local bed topography and partial mobility is the dominant transport process. In contrast, variations in bedload transport rates decrease during high flows when the flow is less sensitive to variations in bed topography and the bed becomes fully mobile.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":null,"pages":null},"PeriodicalIF":5.4,"publicationDate":"2024-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141732712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Devon Kerins, Kayalvizhi Sadayappan, Wei Zhi, Pamela L. Sullivan, Kenneth H. Williams, Rosemary W. H. Carroll, Holly R. Barnard, Matthias Sprenger, Wenming Dong, Julia Perdrial, Li Li
Terrestrial production and export of dissolved organic and inorganic carbon (DOC and DIC) to streams depends on water flow and biogeochemical processes in and beneath soils. Yet, understanding of these processes in a rapidly changing climate is limited. Using the watershed-scale reactive-transport model BioRT-HBV and stream data from a snow-dominated catchment in the Rockies, we show deeper groundwater flow averaged about 20% of annual discharge, rising to ∼35% in drier years. DOC and DIC production and export peaked during snowmelt and wet years, driven more by hydrology than temperature. DOC was primarily produced in shallow soils (1.94 ± 1.45 gC/m2/year), stored via sorption, and flushed out during snowmelt. Some DOC was recharged to and further consumed in the deeper subsurface via respiration (−0.27 ± 0.02 gC/m2/year), therefore reducing concentrations in deeper groundwater and stream DOC concentrations at low discharge. Consequently, DOC was primarily exported from the shallow zone (1.62 ± 0.96 gC/m2/year, compared to 0.12 ± 0.02 gC/m2/year from the deeper zone). DIC was produced in both zones but at higher rates in shallow soils (1.34 ± 1.00 gC/m2/year) than in the deep subsurface (0.36 ± 0.02 gC/m2/year). Deep respiration elevated DIC concentrations in the deep zone and stream DIC concentrations at low discharge. In other words, deep respiration is responsible for the commonly-observed increasing DOC concentrations (flushing) and decreasing DIC concentrations (dilution) with increasing discharge. DIC export from the shallow zone was ~66% of annual export but can drop to ∼53% in drier years. Numerical experiments suggest lower carbon production and export in a warmer, drier future, and a higher proportion from deeper flow and respiration processes. These results underscore the often-overlooked but growing importance of deeper processes in a warming climate.
{"title":"Hydrology Outweighs Temperature in Driving Production and Export of Dissolved Carbon in a Snowy Mountain Catchment","authors":"Devon Kerins, Kayalvizhi Sadayappan, Wei Zhi, Pamela L. Sullivan, Kenneth H. Williams, Rosemary W. H. Carroll, Holly R. Barnard, Matthias Sprenger, Wenming Dong, Julia Perdrial, Li Li","doi":"10.1029/2023wr036077","DOIUrl":"https://doi.org/10.1029/2023wr036077","url":null,"abstract":"Terrestrial production and export of dissolved organic and inorganic carbon (DOC and DIC) to streams depends on water flow and biogeochemical processes in and beneath soils. Yet, understanding of these processes in a rapidly changing climate is limited. Using the watershed-scale reactive-transport model BioRT-HBV and stream data from a snow-dominated catchment in the Rockies, we show deeper groundwater flow averaged about 20% of annual discharge, rising to ∼35% in drier years. DOC and DIC production and export peaked during snowmelt and wet years, driven more by hydrology than temperature. DOC was primarily produced in shallow soils (1.94 ± 1.45 gC/m<sup>2</sup>/year), stored via sorption, and flushed out during snowmelt. Some DOC was recharged to and further consumed in the deeper subsurface via respiration (−0.27 ± 0.02 gC/m<sup>2</sup>/year), therefore reducing concentrations in deeper groundwater and stream DOC concentrations at low discharge. Consequently, DOC was primarily exported from the shallow zone (1.62 ± 0.96 gC/m<sup>2</sup>/year, compared to 0.12 ± 0.02 gC/m<sup>2</sup>/year from the deeper zone). DIC was produced in both zones but at higher rates in shallow soils (1.34 ± 1.00 gC/m<sup>2</sup>/year) than in the deep subsurface (0.36 ± 0.02 gC/m<sup>2</sup>/year). Deep respiration elevated DIC concentrations in the deep zone and stream DIC concentrations at low discharge. In other words, deep respiration is responsible for the commonly-observed increasing DOC concentrations (flushing) and decreasing DIC concentrations (dilution) with increasing discharge. DIC export from the shallow zone was ~66% of annual export but can drop to ∼53% in drier years. Numerical experiments suggest lower carbon production and export in a warmer, drier future, and a higher proportion from deeper flow and respiration processes. These results underscore the often-overlooked but growing importance of deeper processes in a warming climate.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":null,"pages":null},"PeriodicalIF":5.4,"publicationDate":"2024-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141746575","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Extensive experiments have demonstrated that fluid flow in low-permeability media deviates from Darcy's law at low pressure gradients, which is called pre-Darcy flow. Although numerous pre-Darcy flow models have been proposed, these models generally contain one or more empirical parameters with no clear physical meaning. In this paper, we present a simple unified model to describe pre-Darcy flow in porous media by introducing the concept of loss permeability. The physical meaning of the loss permeability parameter and its relationship to permeability are analyzed. Based on the statistics of the loss permeability parameter results of 24 core samples, we found that there is a good positive correlation between the loss permeability parameter and the absolute permeability. A smaller loss permeability indicates a stronger fluid-solid interaction and a stronger nonlinearity between the flow velocity and the pressure gradient. Taking a one-dimensional linear unsteady flow of a slightly compressible fluid in a homogeneous porous medium as an example, we solve the pressure diffusion equation based on the proposed model using a finite difference method. Our results demonstrate that the rate of pressure propagation for pre-Darcy flow is slower than that for Darcy flow for the entire observation period, which corrects previous conclusions. This study is highly important for improving the understanding of fluid flow in low-permeability media.
{"title":"From Pre-Darcy Flow to Darcy Flow in Porous Media: A Simple Unified Model","authors":"Hui Cheng, Fugang Wang, Shengwei Li, Zhongle Cheng, Yilong Yuan, Guanhong Feng","doi":"10.1029/2023wr036902","DOIUrl":"https://doi.org/10.1029/2023wr036902","url":null,"abstract":"Extensive experiments have demonstrated that fluid flow in low-permeability media deviates from Darcy's law at low pressure gradients, which is called pre-Darcy flow. Although numerous pre-Darcy flow models have been proposed, these models generally contain one or more empirical parameters with no clear physical meaning. In this paper, we present a simple unified model to describe pre-Darcy flow in porous media by introducing the concept of loss permeability. The physical meaning of the loss permeability parameter and its relationship to permeability are analyzed. Based on the statistics of the loss permeability parameter results of 24 core samples, we found that there is a good positive correlation between the loss permeability parameter and the absolute permeability. A smaller loss permeability indicates a stronger fluid-solid interaction and a stronger nonlinearity between the flow velocity and the pressure gradient. Taking a one-dimensional linear unsteady flow of a slightly compressible fluid in a homogeneous porous medium as an example, we solve the pressure diffusion equation based on the proposed model using a finite difference method. Our results demonstrate that the rate of pressure propagation for pre-Darcy flow is slower than that for Darcy flow for the entire observation period, which corrects previous conclusions. This study is highly important for improving the understanding of fluid flow in low-permeability media.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":null,"pages":null},"PeriodicalIF":5.4,"publicationDate":"2024-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141732727","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The saltwater-freshwater mixing zones in coastal aquifers can host complex physical exchange and biogeochemical transformations. The land-sourced dense contaminant plumes could be transferred into the mixing zone of the saltwater wedge due to the density effect prior to discharge to the sea. However, the mixing process between dense contaminants and the saltwater wedge has not received much attention, largely due to the lack of physical evidence. This study used laboratory experiments and numerical simulations to investigate the transport and discharge behaviors of variable-density contaminant plumes in tidally influenced unconfined coastal aquifers. Results demonstrate that the highly dense contaminants mix with the underlying saltwater and finally merge with the saltwater wedge. This process significantly extends the contaminant discharge durations, thereby reducing the peak value of contaminant efflux. The dense contaminants are elongated along the landward margin of the saltwater wedge, leading to a larger spreading area (Ms) than that of constant-density contaminants. The sensitivity analysis indicates that the high density of contaminants acts as a trigger to induce the mixing of them and wedges. The higher hydraulic conductivity, lower dispersivities and reduced inland freshwater flux significantly increase the residence times (Rt) and discharge duration (Dt) by enhancing the mixing of dense contaminants with seawater. In contrast, both Rt and Dt values are not only non-monotonic functions of tidal amplitudes but also less sensitive to tidal effects. Compared with the non-tidal condition, however, the addition of tides significantly increases both Rt and Ms values of dense contaminant plumes. The results presented herein provide valuable insights into the mechanisms of dense contaminants mixing into saltwater wedges, which could guide practitioners in designing effective strategies to protect coastal environments from land-sourced contaminants.
沿海含水层中的咸淡水混合区可以承载复杂的物理交换和生物地球化学转化。陆源高密度污染物羽流在排入海洋之前，可能会因密度效应而转移到咸水楔混合区。然而，高密度污染物与咸水楔之间的混合过程并未受到广泛关注，这主要是由于缺乏物理证据。本研究利用实验室实验和数值模拟，研究了受潮汐影响的无约束沿海含水层中可变密 度污染物羽流的迁移和排放行为。结果表明，高密度污染物与下层咸水混合，最后与咸水楔合并。这一过程大大延长了污染物的排放时间，从而降低了污染物流出的峰值。高密度污染物沿盐水楔的向陆边缘伸长，导致其扩散面积（Ms）大于恒定密度污染物的扩散面积（Ms）。敏感性分析表明，高密度污染物是诱发污染物与楔形体混合的触发因素。较高的水力传导性、较低的分散性和减少的内陆淡水流量通过加强高密度污染物与海水的混合，显著增加了停留时间（Rt）和排放持续时间（Dt）。相比之下，Rt 和 Dt 值不仅是潮汐振幅的非单调函数，而且对潮汐效应也不太敏感。然而，与无潮汐条件相比，潮汐的加入会显著增加高密度污染物羽流的 Rt 和 Ms 值。本文介绍的结果为了解高密度污染物混入咸水楔的机理提供了宝贵的启示，可以指导实践者设计有效的策略来保护沿岸环境免受陆源污染物的影响。
{"title":"Dense Contaminants Mixing Into the Saltwater Wedge in Coastal Aquifers: Laboratory and Numerical Investigations","authors":"Jiaxu Zhang, Chunhui Lu, Chenming Zhang","doi":"10.1029/2024wr037452","DOIUrl":"https://doi.org/10.1029/2024wr037452","url":null,"abstract":"The saltwater-freshwater mixing zones in coastal aquifers can host complex physical exchange and biogeochemical transformations. The land-sourced dense contaminant plumes could be transferred into the mixing zone of the saltwater wedge due to the density effect prior to discharge to the sea. However, the mixing process between dense contaminants and the saltwater wedge has not received much attention, largely due to the lack of physical evidence. This study used laboratory experiments and numerical simulations to investigate the transport and discharge behaviors of variable-density contaminant plumes in tidally influenced unconfined coastal aquifers. Results demonstrate that the highly dense contaminants mix with the underlying saltwater and finally merge with the saltwater wedge. This process significantly extends the contaminant discharge durations, thereby reducing the peak value of contaminant efflux. The dense contaminants are elongated along the landward margin of the saltwater wedge, leading to a larger spreading area (<i>M</i><sub><i>s</i></sub>) than that of constant-density contaminants. The sensitivity analysis indicates that the high density of contaminants acts as a trigger to induce the mixing of them and wedges. The higher hydraulic conductivity, lower dispersivities and reduced inland freshwater flux significantly increase the residence times (<i>R</i><sub><i>t</i></sub>) and discharge duration (<i>D</i><sub><i>t</i></sub>) by enhancing the mixing of dense contaminants with seawater. In contrast, both <i>R</i><sub><i>t</i></sub> and <i>D</i><sub><i>t</i></sub> values are not only non-monotonic functions of tidal amplitudes but also less sensitive to tidal effects. Compared with the non-tidal condition, however, the addition of tides significantly increases both <i>R</i><sub><i>t</i></sub> and <i>M</i><sub><i>s</i></sub> values of dense contaminant plumes. The results presented herein provide valuable insights into the mechanisms of dense contaminants mixing into saltwater wedges, which could guide practitioners in designing effective strategies to protect coastal environments from land-sourced contaminants.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":null,"pages":null},"PeriodicalIF":5.4,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141726415","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We recently developed a dynamically coupled hydrological-ocean modeling system that provides seamless coverage across the land-ocean continuum during hurricane-induced compound flooding. This study introduced a local inertial equation and a diagonal flow algorithm to the overland routing of the coupled system’s hydrology model (WRF-Hydro). Using Hurricane Florence (2018) as a test case, the performance of the coupled model was significantly improved, evidenced by its enhanced capability of capturing backwater and increased water level simulation accuracy and stability. With four model experiments, we present a framework to detangle, define, and quantify compound and nonlinear effects. The results revealed that the flood peaks in the lower Cape Fear River Basin and the coastal waters were contributed by inland flooding and storm surge, respectively. These two processes had comparable contributions to the flooding in the Cape Fear River Estuary. The compound effect was identified when the flood levels resulting from the combination of land and ocean processes surpassed those caused by an individual process alone. The compound effect during Hurricane Florence exhibited limited impact on flood peaks, primarily due to the time lag between the peaks of the storm surge and the inland flooding. In the period between the two peaks, the compound effect was salient and significantly impacted the magnitude and variation of the flood level. The nonlinear effect, defined as the difference between the compound flood level and the superposition of storm surge and inland flooding water levels, reduced flood levels in the river channels while increasing flood levels on the floodplain.
{"title":"Quantifying Compound and Nonlinear Effects of Hurricane-Induced Flooding Using a Dynamically Coupled Hydrological-Ocean Model","authors":"Daoyang Bao, Z. George Xue, John C. Warner","doi":"10.1029/2023wr036455","DOIUrl":"https://doi.org/10.1029/2023wr036455","url":null,"abstract":"We recently developed a dynamically coupled hydrological-ocean modeling system that provides seamless coverage across the land-ocean continuum during hurricane-induced compound flooding. This study introduced a local inertial equation and a diagonal flow algorithm to the overland routing of the coupled system’s hydrology model (WRF-Hydro). Using Hurricane Florence (2018) as a test case, the performance of the coupled model was significantly improved, evidenced by its enhanced capability of capturing backwater and increased water level simulation accuracy and stability. With four model experiments, we present a framework to detangle, define, and quantify compound and nonlinear effects. The results revealed that the flood peaks in the lower Cape Fear River Basin and the coastal waters were contributed by inland flooding and storm surge, respectively. These two processes had comparable contributions to the flooding in the Cape Fear River Estuary. The compound effect was identified when the flood levels resulting from the combination of land and ocean processes surpassed those caused by an individual process alone. The compound effect during Hurricane Florence exhibited limited impact on flood peaks, primarily due to the time lag between the peaks of the storm surge and the inland flooding. In the period between the two peaks, the compound effect was salient and significantly impacted the magnitude and variation of the flood level. The nonlinear effect, defined as the difference between the compound flood level and the superposition of storm surge and inland flooding water levels, reduced flood levels in the river channels while increasing flood levels on the floodplain.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":null,"pages":null},"PeriodicalIF":5.4,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141631709","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Vietnamese Mekong Delta (VMD) is the most productive region in Vietnam in terms of agriculture and aquaculture. Unsurprisingly, droughts have been a prevalent concern for stakeholders across the VMD over the past decades. However, the VMD precipitation moisture sources and their dominant factors during drought conditions were not well understood. Using the ERA5 reanalysis data as inputs, the Water Accounting Model-2layers (WAM-2layers), a moisture tracking tool, was applied to identify the VMD precipitation moisture sources from 1980 to 2020. The modeling simulation indicates that the moisture sources transported from the upwind regions dominate the VMD precipitation by 60.4%–93.3%, and the moisture source areas vary seasonally with different monsoon types. Results of the causal inference algorithms indicate that the humidity and wind speed in the upwind area are the dominant factors for driving moisture transport and determining the amount of VMD precipitation in dry and wet seasons, respectively. The local atmospheric conditions may also have a causal effect on moisture recycling. During the drought events in 2015–2016 and 2019–2020, the reduced moisture transport in the 2016 dry season was mainly caused by the anomalies in both humidity and wind speed, while the below average moisture sources in the 2020 dry season were dominated by humidity. In the 2019 wet season, an anomaly in wind speed led to a decrease in the tracked moisture. These findings are of great significance for understanding the moisture sources of precipitation and further improving drought prediction in the VMD.
{"title":"Understanding Precipitation Moisture Sources and Their Dominant Factors During Droughts in the Vietnamese Mekong Delta","authors":"Keke Zhou, Xiaogang Shi","doi":"10.1029/2023wr035920","DOIUrl":"https://doi.org/10.1029/2023wr035920","url":null,"abstract":"The Vietnamese Mekong Delta (VMD) is the most productive region in Vietnam in terms of agriculture and aquaculture. Unsurprisingly, droughts have been a prevalent concern for stakeholders across the VMD over the past decades. However, the VMD precipitation moisture sources and their dominant factors during drought conditions were not well understood. Using the ERA5 reanalysis data as inputs, the Water Accounting Model-2layers (WAM-2layers), a moisture tracking tool, was applied to identify the VMD precipitation moisture sources from 1980 to 2020. The modeling simulation indicates that the moisture sources transported from the upwind regions dominate the VMD precipitation by 60.4%–93.3%, and the moisture source areas vary seasonally with different monsoon types. Results of the causal inference algorithms indicate that the humidity and wind speed in the upwind area are the dominant factors for driving moisture transport and determining the amount of VMD precipitation in dry and wet seasons, respectively. The local atmospheric conditions may also have a causal effect on moisture recycling. During the drought events in 2015–2016 and 2019–2020, the reduced moisture transport in the 2016 dry season was mainly caused by the anomalies in both humidity and wind speed, while the below average moisture sources in the 2020 dry season were dominated by humidity. In the 2019 wet season, an anomaly in wind speed led to a decrease in the tracked moisture. These findings are of great significance for understanding the moisture sources of precipitation and further improving drought prediction in the VMD.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":null,"pages":null},"PeriodicalIF":5.4,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141631708","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fujian Li, Yuqi Shan, Ming Li, Yakun Guo, Chao Liu
River restoration projects often involve vegetation planting to retain sediment and stabilize riverbanks. Laboratory experiments have explored the impact of rigid emergent vegetation canopies on bed morphology. Inside canopies, bed erosion is attributed to vegetation-induced turbulent kinetic energy (TKE). Based on the in-canopy local TKE and the criteria for sediment movement, a method is established and validated for predicting the length of the bed erosion region. In the bare channel, bed erosion is related to the ratio of canopy length to flow adjustment distance, L/LI, and exhibits two trends. At L/LI < 1, the maximum depth, ds(bare), and length, Ls(bare), of the bed erosion region increase with increasing canopy length. At L/LI ≥ 1, ds(bare) and Ls(bare) are not influenced by the canopy length and remain constant. In vegetated regions with the same length and plant density, discontinuous canopies (streamwise interval s ≥ canopy width D) yield weaker bed erosion than continuous canopies. The mutual influence between two canopies must be considered if the canopy interval satisfies s < 3D. These results provide insights for designing vegetation canopies for river restoration projects.
{"title":"Insights for River Restoration: The Impacts of Vegetation Canopy Length and Canopy Discontinuity on Riverbed Evolution","authors":"Fujian Li, Yuqi Shan, Ming Li, Yakun Guo, Chao Liu","doi":"10.1029/2023wr036473","DOIUrl":"https://doi.org/10.1029/2023wr036473","url":null,"abstract":"River restoration projects often involve vegetation planting to retain sediment and stabilize riverbanks. Laboratory experiments have explored the impact of rigid emergent vegetation canopies on bed morphology. Inside canopies, bed erosion is attributed to vegetation-induced turbulent kinetic energy (<i>TKE</i>). Based on the in-canopy local <i>TKE</i> and the criteria for sediment movement, a method is established and validated for predicting the length of the bed erosion region. In the bare channel, bed erosion is related to the ratio of canopy length to flow adjustment distance, <i>L</i>/<i>L</i><sub><i>I</i></sub>, and exhibits two trends. At <i>L</i>/<i>L</i><sub><i>I</i></sub> < 1, the maximum depth, <i>d</i><sub><i>s</i>(<i>bare</i>)</sub>, and length, <i>L</i><sub><i>s</i>(<i>bare</i>)</sub>, of the bed erosion region increase with increasing canopy length. At <i>L</i>/<i>L</i><sub><i>I</i></sub> ≥ 1, <i>d</i><sub><i>s</i>(<i>bare</i>)</sub> and <i>L</i><sub><i>s</i>(<i>bare</i>)</sub> are not influenced by the canopy length and remain constant. In vegetated regions with the same length and plant density, discontinuous canopies (streamwise interval <i>s</i> ≥ canopy width <i>D</i>) yield weaker bed erosion than continuous canopies. The mutual influence between two canopies must be considered if the canopy interval satisfies <i>s</i> < 3<i>D</i>. These results provide insights for designing vegetation canopies for river restoration projects.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":null,"pages":null},"PeriodicalIF":5.4,"publicationDate":"2024-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141631803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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