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Special Issue "Streambank Erosion: Monitoring, Modeling and Management"

A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Hydraulics".

Deadline for manuscript submissions: closed (31 January 2018)

Special Issue Editors

Guest Editor
Prof. Garey A. Fox

North Carolina State University
E-Mail
Phone: 919-515-6700
Interests: stream/aquifer interaction; streambank erosion and failure; seepage erosion; subsurface nutrient transport; vegetative filter strips; and contaminant transport modeling
Guest Editor
Dr. Celso Castro-Bolinaga

North Carolina State University
E-Mail
Phone: 919-515-6712
Interests: environmental fluid mechanics; transport of coarse- and fine-grained sediment; computational fluid dynamics; predictive capability of hydrodynamic and morphodynamic numerical models

Special Issue Information

Dear Colleagues,

The purpose of this Special Issue is to compile recent progress and new research directions on streambank monitoring, modeling, and management. Streambank erosion is recognized as a significant contributor to total watershed sediment and nutrient loading. In many Conservation Effects Assessment Project (CEAP) watersheds in the United States, for example, sediment eroded from banks is one of the primary sources of bed material in streams, even when compared to upland sediment sources 1. Nowadays, technologies such as terrestrial and airborne LIDAR, unmanned aerial systems, and drones are opening new avenues for a more detailed streambank erosion monitoring. In-stream sediment concentration remains one of the more poorly quantified water quality parameters due to the difficulty in obtaining accurate estimates of sediment transport. New techniques for measuring bed-load and suspended-sediment transport that aim to address this limitation, including acoustic Doppler current profilers, laser diffraction, optical sediment flux, and pressure differential and bulk optics, warrant further attention and assessment, particularly when applied to a wide variety of stream types. Current channel modification strategies place a heavy emphasis on channel form rather than on physically-based processes. Typically, a standardized approach that relies on channel classification is applied to stream restoration and stabilization projects. This method often relies on creating a certain channel form from a reference reach that is considered “good”; however, this channel form may not be suitable for the amount of sediment or the valley slope. Therefore, there is a need to assess the performance and suitability of these standardized approaches, as well as to better understand the contribution of process-based models in evaluating stabilization and restoration efforts. Such advances will allow the research and management communities to better address the benefit of various conservation and/or stabilization practices at targeted locations within watersheds.

1Tomer, M.D.; Locke, M.A. The challenge of documenting water quality benefits of conservation practices: A review of USDAARS’s Conservation Effects Assessment Project watershed studies. Water Sci. Technol. 2001, 64, 300–310.

Prof. Garey A. Fox
Dr. Celso Castro-Bolinaga
Guest Editors

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Keywords

  • Bank stability
  • Computational fluid dynamics
  • Fluvial erosion
  • Hydrodynamic models
  • Monitoring
  • Morphodynamic models
  • Streambank stabilization
  • Transport of coarse- and fine-grained sediment.

Published Papers (15 papers)

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Editorial

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Open AccessEditorial Streambank Erosion: Advances in Monitoring, Modeling and Management
Water 2018, 10(10), 1346; https://doi.org/10.3390/w10101346
Received: 31 August 2018 / Revised: 17 September 2018 / Accepted: 26 September 2018 / Published: 28 September 2018
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Abstract
The special issue “Streambank Erosion: Monitoring, Modeling, and Management” presents recent progress and outlines new research directions through the compilation of 14 research articles that cover topics relevant to the monitoring, modeling, and management of this morphodynamic process. It contributes to our advancement
[...] Read more.
The special issue “Streambank Erosion: Monitoring, Modeling, and Management” presents recent progress and outlines new research directions through the compilation of 14 research articles that cover topics relevant to the monitoring, modeling, and management of this morphodynamic process. It contributes to our advancement and understanding of how monitoring campaigns can characterize the effect of external drivers, what the capabilities and limitations of numerical models are when predicting the response of the system, and what the effectiveness of different management practices is in order to prevent and mitigate streambank erosion and failure. The present editorial paper summarizes the main outcomes of the special issue, and further expands on some of the remaining challenges within the realm of monitoring, modeling, and managing streambank erosion and failure. First, it highlights the need to better understand the non-linear behavior of erosion rates with increasing applied boundary shear stress when predicting cohesive soil detachment, and accordingly, to adjust the computational procedures that are currently used to obtain erodibility parameters; and second, it emphasizes the need to incorporate process-based modeling of streambank erosion and failure in the design and assessment of stream restoration projects. Full article
(This article belongs to the Special Issue Streambank Erosion: Monitoring, Modeling and Management)
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Research

Jump to: Editorial

Open AccessArticle Comparing the Sensitivity of Bank Retreat to Changes in Biophysical Conditions between Two Contrasting River Reaches Using a Coupled Morphodynamic Model
Water 2018, 10(4), 518; https://doi.org/10.3390/w10040518
Received: 22 March 2018 / Revised: 17 April 2018 / Accepted: 18 April 2018 / Published: 20 April 2018
Cited by 2 | PDF Full-text (5116 KB) | HTML Full-text | XML Full-text
Abstract
Morphodynamic models of river meandering patterns and dynamics are based on the premise that the integration of biophysical processes matching those operating in natural rivers should result in a better fit with observations. Only a few morphodynamic models have been applied to natural
[...] Read more.
Morphodynamic models of river meandering patterns and dynamics are based on the premise that the integration of biophysical processes matching those operating in natural rivers should result in a better fit with observations. Only a few morphodynamic models have been applied to natural rivers, typically along short reaches, and the relative importance of biophysical parameters remains largely unknown in these cases. Here, a series of numerical simulations were run using the hydrodynamic solver TELEMAC-2D, coupled to an advanced physics-based geotechnical module, to verify if sensitivity to key biophysical conditions differs substantially between two natural meandering reaches of different scale and geomorphological context. The model was calibrated against observed measurements of bank retreat for a 1.5 km semi-alluvial meandering reach incised into glacial till (Medway Creek, Ontario, Canada) and an 8.6 km long sinuous alluvial reach of the St. François River (Quebec, Canada). The two river reaches have contrasting bed and bank composition, and they differ in width by one order of magnitude. Calibration was performed to quantify and contrast the contribution of key geotechnical parameters, such as bank cohesion, to bank retreat. Results indicate that the sensitivity to key geotechnical parameters is dependent on the biophysical context and highly variable at the sub-reach scale. The homogeneous sand-bed St. François River is less sensitive to cohesion and friction angle than the more complex Medway Creek, flowing through glacial-till deposits. The latter highlights the limits of physics-based models for practical purposes, as the amount and spatial resolution of biophysical parameters required to improve the agreement between simulation results and observations may justify the use of a reduced complexity modelling approach. Full article
(This article belongs to the Special Issue Streambank Erosion: Monitoring, Modeling and Management)
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Open AccessArticle Modeling Streambank and Artificial Gravel Deposit Erosion for Sediment Replenishment
Water 2018, 10(4), 508; https://doi.org/10.3390/w10040508
Received: 14 February 2018 / Revised: 11 April 2018 / Accepted: 13 April 2018 / Published: 19 April 2018
Cited by 1 | PDF Full-text (10741 KB) | HTML Full-text | XML Full-text
Abstract
Sediment replenishment by artificial gravel deposits is a measure to increase sediment supply in gravel-bed rivers. Thereby, streambank erosion is the dominant process for gravel entrainment. In this contribution, we quantitatively validate a numerical morphodynamic 2D model and the relevant model approaches to
[...] Read more.
Sediment replenishment by artificial gravel deposits is a measure to increase sediment supply in gravel-bed rivers. Thereby, streambank erosion is the dominant process for gravel entrainment. In this contribution, we quantitatively validate a numerical morphodynamic 2D model and the relevant model approaches to reproduce non-cohesive streambank erosion. Therefore, a calibration and a sensitivity analysis of the relevant model approaches and parameters are carried out based on a reference laboratory experiment on streambank erosion in a straight channel from the literature. The relevant model approaches identified to successfully reproduce lateral streambank erosion are the gravitational bank collapse, the lateral bed slope effect on the bed load transport direction and the local bed slope effect on the critical Shields stress. Based on these findings, the numerical model was compared against data from laboratory experiments on gravel deposit erosion. Thereby, the focus was on the influence of the hydraulic discharge, the grain size distribution of the sediment and the geometrical quantities of the gravel deposits, such as the width, height and length of the deposit. It is shown that the dynamics of the erosion process were well reproduced by the numerical model using non-uniform sediment. Furthermore, the erosion rates were in good agreement with the laboratory experiments, except for the initial phase of the experiments, where the erosion rates were highest and settling of the gravel deposit was observed in the laboratory experiments. Overall, the numerical model proved to be a suitable tool to predict the erosion process of artificial gravel deposits, and hence, can be recommended for the design of sediment replenishment measures. Full article
(This article belongs to the Special Issue Streambank Erosion: Monitoring, Modeling and Management)
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Open AccessFeature PaperArticle Effects of Bank Vegetation and Incision on Erosion Rates in an Urban Stream
Water 2018, 10(4), 482; https://doi.org/10.3390/w10040482
Received: 31 January 2018 / Revised: 8 April 2018 / Accepted: 12 April 2018 / Published: 14 April 2018
Cited by 1 | PDF Full-text (15118 KB) | HTML Full-text | XML Full-text
Abstract
Changing land-use associated with urbanization has resulted in shifts in riparian assemblages, stream hydraulics, and sediment dynamics leading to the degradation of waterways. To combat degradation, restoration and management of riparian zones is becoming increasingly common. However, the relationship between flora, especially the
[...] Read more.
Changing land-use associated with urbanization has resulted in shifts in riparian assemblages, stream hydraulics, and sediment dynamics leading to the degradation of waterways. To combat degradation, restoration and management of riparian zones is becoming increasingly common. However, the relationship between flora, especially the influence of invasive species, on sediment dynamics is poorly understood. Bank erosion and turbidity were monitored in the Tookany Creek and its tributary Mill Run in the greater Philadelphia, PA region. To evaluate the influence of the invasive species Reynoutria japonica (Japanese knotweed) on erosion, reaches were chosen based on their riparian vegetation and degree of incision. Bank pins and turbidity loggers were used to estimate sediment erosion. Erosion calculations based on bank pins suggest greater erosion in reaches dominated by knotweed than those dominated by trees. For a 9.5-month monitoring period, there was 29 cm more erosion on banks that were also incised, and 9 cm more erosion in banks with little incision. Turbidity responses to storm events were also higher (77 vs. 54 NTU (nephelometric turbidity unit)) in reaches with knotweed, although this increase was found when the reach dominated by knotweed was also incised. Thus, this study linked knotweed to increased erosion using multiple methods. Full article
(This article belongs to the Special Issue Streambank Erosion: Monitoring, Modeling and Management)
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Open AccessArticle Assessment of Practices for Controlling Shallow Valley-Bottom Gullies in the Sub-Humid Ethiopian Highlands
Water 2018, 10(4), 389; https://doi.org/10.3390/w10040389
Received: 1 February 2018 / Revised: 14 March 2018 / Accepted: 16 March 2018 / Published: 27 March 2018
Cited by 1 | PDF Full-text (60182 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Rehabilitation of large valley bottom gullies in developing countries is hampered by high cost. Stopping head cuts at the time of initiation will prevent large gullies from forming and is affordable. However, research on practices to control shallow gully heads with local materials
[...] Read more.
Rehabilitation of large valley bottom gullies in developing countries is hampered by high cost. Stopping head cuts at the time of initiation will prevent large gullies from forming and is affordable. However, research on practices to control shallow gully heads with local materials is limited. The objective of this research was therefore to identify cost-effective shallow gully head stabilization practices. The four-year study was conducted on 14 shallow gullies (<3 m deep) in the central Ethiopian highlands. Six gullies were used as a control. Heads in the remaining eight gullies were regraded to a 1:1 slope. Additional practices implemented were adding either riprap or vegetation or both on the regraded heads and stabilizing the gully bed downstream. Gully heads were enclosed by fencing to prohibit cattle access to the planted vegetation. The median yearly head retreat of the control gullies was 3.6 m a−1 with a maximum of 23 m a−1. Vegetative treatments without riprap prevented gully incision by trapping sediments but did not stop the upslope retreat. The gully heads protected by riprap did not erode. Regrading the slope and adding riprap was most effective in controlling gully head retreat, and with hay grown on the fenced-in areas around the practice, it was profitable for farmers. Full article
(This article belongs to the Special Issue Streambank Erosion: Monitoring, Modeling and Management)
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Open AccessArticle Effect of Meteorological Patterns on the Intensity of Streambank Erosion in a Proglacial Gravel-Bed River (Spitsbergen)
Water 2018, 10(3), 320; https://doi.org/10.3390/w10030320
Received: 16 February 2018 / Revised: 9 March 2018 / Accepted: 12 March 2018 / Published: 14 March 2018
Cited by 2 | PDF Full-text (5037 KB) | HTML Full-text | XML Full-text
Abstract
Lower parts of proglacial rivers are commonly assumed to be characterised by a multiannual aggradation trend, and streambank erosion is considered to occur rarely and locally. In the years 2009–2013, detailed measurements of channel processes were performed in the Scott River (SW Spitsbergen).
[...] Read more.
Lower parts of proglacial rivers are commonly assumed to be characterised by a multiannual aggradation trend, and streambank erosion is considered to occur rarely and locally. In the years 2009–2013, detailed measurements of channel processes were performed in the Scott River (SW Spitsbergen). More than 60% of its surface area (10 km2) occupies non-glaciated valleys. Since the end of the Little Ice Age, the Scott Glacier has been subject to intensive retreat, resulting in the expansion of the terminoglacial and paraglacial zones. In this area, the Scott River develops an alluvial valley with a proglacial river, which has led to a comparatively low rate of fluvial transport, dominance of suspension over bedload, and the occurrence of various channel patterns. Measurements, performed in the lower course of the valley in two fixed cross-sections of the Scott River channel, document variable annual tendencies with a prevalence of scour over deposition processes in the channel bottom. The balance of scour and fill also differs in particular measurement cross-sections and during the summer season. The maximum erosion indices (1.7 m2) were related to single periods of floods with snow-glacier melt and rainfall origin. The contribution of streambank erosion was usually lower than that of deep erosion both in the annual cycle and during extreme events. The channel-widening index also suggests variable annual (from −1 m to +1 m) and inter-annual tendencies. During a three-day flood from August 2013, in a measurement profile at the mouth of the river, the NNW bank was laterally shifted by as much as 3 m. Annual and inter-seasonal indices of total channel erosion, however, show that changes in the channel-bottom morphology are equalised relatively fast, and in terms of balance the changes usually do not exceed 0.5% of a cross section’s area. Full article
(This article belongs to the Special Issue Streambank Erosion: Monitoring, Modeling and Management)
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Open AccessArticle Estimating Erodibility Parameters for Streambanks with Cohesive Soils Using the Mini Jet Test Device: A Comparison of Field and Computational Methods
Water 2018, 10(3), 304; https://doi.org/10.3390/w10030304
Received: 28 January 2018 / Revised: 28 February 2018 / Accepted: 6 March 2018 / Published: 11 March 2018
Cited by 1 | PDF Full-text (3076 KB) | HTML Full-text | XML Full-text
Abstract
The jet test device has been predominantly used for in situ critical shear stress (τc) and erodibility coefficient (kd) measurements of cohesive streambanks/beds using three analytical procedures: the Blaisdell method (BM), the iterative approach (IP), and the
[...] Read more.
The jet test device has been predominantly used for in situ critical shear stress (τc) and erodibility coefficient (kd) measurements of cohesive streambanks/beds using three analytical procedures: the Blaisdell method (BM), the iterative approach (IP), and the scour depth approach (SDP). Existing studies have reported that τc and kd estimates can be influenced by the computational procedure, time intervals for scour-hole depth measurements, and the pressure head selection. This study compared estimates of τc and kd among the three computational procedures using single and multiple pressure settings (SPS, MPS). A new method is introduced applying incrementally increasing pressure heads, hypothesizing depth-averaged erodibility parameters would be generated that better represent bank and fluvial erosion. Estimates of τc applying the MPS-BM procedure were greater by 17% to 100% compared with SPS-BM procedures and kd estimates were lower with less variability (σ = 3.54) compared with other procedures from 126 jet tests among 21 Tennessee stream sites. This finding supports the hypothesis of increasing τc and decreasing kd with greater soil depths into the bank, suggesting the MPS-BM procedure can improve the estimation of τc and kd using the mini-jet test device. Overall, this study demonstrates the need to standardize field and computational procedures. Full article
(This article belongs to the Special Issue Streambank Erosion: Monitoring, Modeling and Management)
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Open AccessFeature PaperArticle Water Temperature, pH, and Road Salt Impacts on the Fluvial Erosion of Cohesive Streambanks
Water 2018, 10(3), 302; https://doi.org/10.3390/w10030302
Received: 24 January 2018 / Revised: 4 March 2018 / Accepted: 8 March 2018 / Published: 10 March 2018
Cited by 2 | PDF Full-text (3984 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Increasing human populations and global climate change will severely stress our water resources. One potential unforeseen consequence of these stressors is accelerated stream channel erosion due to increased stream temperatures and changes in stream chemistry, which affect the surface potential and hence the
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Increasing human populations and global climate change will severely stress our water resources. One potential unforeseen consequence of these stressors is accelerated stream channel erosion due to increased stream temperatures and changes in stream chemistry, which affect the surface potential and hence the stability of soil colloids. The objectives of this study were to determine the effect of water temperature, pH, and salinity on streambank erosion rates; determine how erosion rates vary with clay mineralogy; and, explore the relationship between zeta potential and erosion rate. Remolded samples of natural montmorillonite- and vermiculite-dominated soils were eroded in a recirculating hydraulic flume under multiple shear stresses (0.1–20 Pa) with different combinations of water temperature (10, 20, and 30 °C), pH (6 and 8), and deicing salt (0 and 5000 mg/L). The results show that erosion rates significantly increased with increasing water temperature: a 10 °C increase in water temperature increased median erosion rates by as much as a factor of eight. Significant interactions between water pH and salinity also affected erosion rates. In freshwater, erosion rates were inversely related to pH; however, at high salt concentrations, the influence of pH on erosion rates was reduced. Results of this study clearly indicate water chemistry plays a critical role in the fluvial erosion of cohesive streambanks and suggest that channel protection efforts should include controls for stream temperature, in addition to peak flow rates, to maintain channel stability. Full article
(This article belongs to the Special Issue Streambank Erosion: Monitoring, Modeling and Management)
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Open AccessArticle Streambank Alluvial Unit Contributions to Suspended Sediment and Total Phosphorus Loads, Walnut Creek, Iowa, USA
Water 2018, 10(2), 111; https://doi.org/10.3390/w10020111
Received: 16 January 2018 / Revised: 23 January 2018 / Accepted: 25 January 2018 / Published: 28 January 2018
Cited by 2 | PDF Full-text (5368 KB) | HTML Full-text | XML Full-text
Abstract
Streambank erosion may represent a significant source of sediment and phosphorus (P) to overall watershed loads; however, watershed-scale quantification of contributions is rare. In addition, streambanks are often comprised of highly variable stratigraphic source materials (e.g., alluvial deposits), which may differentially impact in-channel
[...] Read more.
Streambank erosion may represent a significant source of sediment and phosphorus (P) to overall watershed loads; however, watershed-scale quantification of contributions is rare. In addition, streambanks are often comprised of highly variable stratigraphic source materials (e.g., alluvial deposits), which may differentially impact in-channel P dynamics once eroded. The objective of this study was to quantify sediment and total phosphorus (TP) losses from four materials comprising streambanks within a 5218 ha watershed in Iowa, USA. Streambank-face surveys, erosion pins, and soil analyses were used to quantify surface area representation, recession, and losses of sediment and TP over a two-year period. Cumulative, whole-bank gross mean recession totaled 18.6 cm over two years, and material-specific gross mean recession ranged from 15.5 to 64.1 cm. Cumulative, whole-bank mean gross mass losses totaled 0.28 Mg sediment and 0.7 × 10−5 Mg TP per meter channel length. Annual sediment losses equated to 4–44% of historic suspended sediment loads. Stratigraphy was significant in gross material erosion and losses, with lower materials (i.e., bank toe region) exhibiting the greatest recession rates and cumulative recession. Weathered/colluvial material dominated total bank face surface area (88.3%), and contributed the greatest proportion of sediment and TP mass loss (66, 68%, respectively) versus other streambank materials. Full article
(This article belongs to the Special Issue Streambank Erosion: Monitoring, Modeling and Management)
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Open AccessFeature PaperArticle Modeling Stream Bank Erosion: Practical Stream Results and Future Needs
Water 2017, 9(12), 950; https://doi.org/10.3390/w9120950
Received: 12 October 2017 / Revised: 29 November 2017 / Accepted: 30 November 2017 / Published: 6 December 2017
Cited by 1 | PDF Full-text (8502 KB) | HTML Full-text | XML Full-text
Abstract
Coupled two-dimensional (2D) morphodynamic and bank erosion models are gaining attentions in recent years. It has been shown that such models have advantages over the one-dimensional (1D) modeling approaches. In this paper, a previous 2D bank erosion model with the moving mesh method
[...] Read more.
Coupled two-dimensional (2D) morphodynamic and bank erosion models are gaining attentions in recent years. It has been shown that such models have advantages over the one-dimensional (1D) modeling approaches. In this paper, a previous 2D bank erosion model with the moving mesh method is extended to include the fixed mesh approach. Further, two practical streams with differing complexity are simulated to demonstrate the extended model. Both the moving mesh and fixed mesh methods are used in the modeling. The model consists of two components: a 2D flow and mobile-bed model for vertical bed changes and hydraulic forces acting on a bank and a lateral bank retreat model. The 2D vertical model and the lateral bank erosion model are coupled together spatially and temporally through a special procedure and a common mesh. With the experiences gained with practical stream modeling, the modeling procedure and key model input parameters are described. The study shows that the moving and fixed mesh methods together make the extended bank erosion model numerically robust and capable of predicting both the vertical bed changes and the lateral stream bank erosion for complex streams. Each individual method, however, has its own limitations in terms of model accuracy and efficiency. The moving mesh works well if bank retreat is relatively small, e.g., less than one channel width, and produces more accurate results than the fixed mesh method. The fixed mesh may be needed for ensuring numerical stability if a bank may be subject to significant retreat (e.g., more than one channel width). The fixed mesh method, however, is less accurate than the moving mesh method and a much refined mesh may be needed. Both methods need future research and improvements in terms of their model accuracy. Full article
(This article belongs to the Special Issue Streambank Erosion: Monitoring, Modeling and Management)
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Open AccessArticle Quantifying Effectiveness of Streambank Stabilization Practices on Cedar River, Nebraska
Water 2017, 9(12), 930; https://doi.org/10.3390/w9120930
Received: 15 September 2017 / Revised: 20 November 2017 / Accepted: 26 November 2017 / Published: 29 November 2017
Cited by 2 | PDF Full-text (5818 KB) | HTML Full-text | XML Full-text
Abstract
Excessive sediment is a major pollutant to surface waters worldwide. In some watersheds, streambanks are a significant source of this sediment, leading to the expenditure of billions of dollars in stabilization projects. Although costly streambank stabilization projects have been implemented worldwide, long-term monitoring
[...] Read more.
Excessive sediment is a major pollutant to surface waters worldwide. In some watersheds, streambanks are a significant source of this sediment, leading to the expenditure of billions of dollars in stabilization projects. Although costly streambank stabilization projects have been implemented worldwide, long-term monitoring to quantify their success is lacking. There is a critical need to document the long-term success of streambank restoration projects. The objectives of this research were to (1) quantify streambank retreat before and after the stabilization of 18 streambanks on the Cedar River in North Central Nebraska, USA; (2) assess the impact of a large flood event; and (3) determine the most cost-efficient stabilization practice. The stabilized streambanks included jetties (10), rock-toe protection (1), slope reduction/gravel bank (1), a retaining wall (1), rock vanes (2), and tree revetments (3). Streambank retreat and accumulation were quantified using aerial images from 1993 to 2016. Though streambank retreat has been significant throughout the study period, a breached dam in 2010 caused major flooding and streambank erosion on the Cedar River. This large-scale flood enabled us to quantify the effect of one extreme event and evaluate the effectiveness of the stabilized streambanks. With a 70% success rate, jetties were the most cost-efficient practice and yielded the most deposition. If minimal risk is unacceptable, a more costly yet immobile practice such as a gravel bank or retaining wall is recommended. Full article
(This article belongs to the Special Issue Streambank Erosion: Monitoring, Modeling and Management)
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Open AccessArticle A Theoretical Model to Predict the Critical Hydraulic Gradient for Soil Particle Movement under Two-Dimensional Seepage Flow
Water 2017, 9(11), 828; https://doi.org/10.3390/w9110828
Received: 7 October 2017 / Revised: 24 October 2017 / Accepted: 26 October 2017 / Published: 29 October 2017
Cited by 2 | PDF Full-text (2704 KB) | HTML Full-text | XML Full-text
Abstract
The soil particle movement under seepage flow is one of the predominant mechanisms responsible for incidents and failures of dams and streambanks. However, little attention has been paid to the critical hydraulic gradient under two-dimensional (2-D) seepage flow. In this study, a theoretical
[...] Read more.
The soil particle movement under seepage flow is one of the predominant mechanisms responsible for incidents and failures of dams and streambanks. However, little attention has been paid to the critical hydraulic gradient under two-dimensional (2-D) seepage flow. In this study, a theoretical model was established under 2-D seepage flow to predict the critical hydraulic gradients for soil particle movement. In this model, the sediment particle rolling theory was used, while taking into account the relative exposure degree of the soil grains and the seepage direction. The model was validated through qualitative analysis and comparison with previous data, and showed considerable superiority over Terzaghi's model. In addition, the effect of the soil internal instability, implying that the critical hydraulic gradient of unstable soil is lower than that of stable soil, was discussed. Various parameters of the model were also analyzed. The results showed that the seepage direction angle was positively related to the critical gradient, whereas the void and the mean diameter of the soil were negatively related to it. Finally, the model proposes a calculation method for the particle movement initiation probability, which is regarded as a key parameter in the sediment transport model. Full article
(This article belongs to the Special Issue Streambank Erosion: Monitoring, Modeling and Management)
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Open AccessArticle Spatial and Temporal Variability of Bank Erosion during the Period 1930–2016: Case Study—Kolubara River Basin (Serbia)
Water 2017, 9(10), 748; https://doi.org/10.3390/w9100748
Received: 3 July 2017 / Revised: 25 September 2017 / Accepted: 27 September 2017 / Published: 29 September 2017
Cited by 4 | PDF Full-text (10034 KB) | HTML Full-text | XML Full-text
Abstract
The fluvial process is characterized by an intense meandering riverbed. The aim of this study was to perform a reconstruction of the lateral migration of a 15 km length of an active meandering river during the period 1930–2016. River morphological changes were analyzed
[...] Read more.
The fluvial process is characterized by an intense meandering riverbed. The aim of this study was to perform a reconstruction of the lateral migration of a 15 km length of an active meandering river during the period 1930–2016. River morphological changes were analyzed and quantified from cadastral maps and aerial photographs as well as by geodetic survey and GIS. Hydrological characteristics and extreme hydrological events were evaluated in relation to bank erosion rate. The rate of bank erosion was markedly different from the long-term studied meanders, just like in the short-term period. During the 87 years of observation (from 1930 to 2016), the length of the Kolubara River was enlarged by 3.44 km. The average migration rate of the Kolubara River for monitored meanders in the period 1930–2010 was 1.9 m·year−1, while in the period 2010–2016, the average migration rate was 3.3 m·year−1. The rate of bank erosion was more intensive across the entire short-term period than during the longer period, and the maximum annual rate of bank erosion during the period 2010–2016 varied between 0.3 and 11.5 m. It is very likely that in the period from 2010, frequent discharge variations and rapid change of its extreme values caused more intensive bank erosion. These research results will be valuable for river channel management, engineering (soft and hard engineering), and planning purposes (predicting changes in river channel form) in the Kolubara River Basin. Full article
(This article belongs to the Special Issue Streambank Erosion: Monitoring, Modeling and Management)
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Open AccessArticle Effects of Intra-Storm Soil Moisture and Runoff Characteristics on Ephemeral Gully Development: Evidence from a No-Till Field Study
Water 2017, 9(10), 742; https://doi.org/10.3390/w9100742
Received: 27 August 2017 / Revised: 24 September 2017 / Accepted: 26 September 2017 / Published: 28 September 2017
Cited by 3 | PDF Full-text (4474 KB) | HTML Full-text | XML Full-text
Abstract
Ephemeral gully erosion, prevalent on agricultural landscapes of the Great Plains, is recognized as a large source of soil loss and a substantial contributor to the sedimentation of small ponds and large reservoirs. Multi-seasonal field studies can provide needed information on ephemeral gully
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Ephemeral gully erosion, prevalent on agricultural landscapes of the Great Plains, is recognized as a large source of soil loss and a substantial contributor to the sedimentation of small ponds and large reservoirs. Multi-seasonal field studies can provide needed information on ephemeral gully development and its relationship to physical factors associated with field characteristics, rainfall patterns, runoff hydrograph, and management practices. In this study, an ephemeral gully on a no-till cultivated crop field in central Kansas, U.S., was monitored in 2013 and 2014. Data collection included continuous sub-hourly precipitation, soil moisture, soil temperature, and 15 field surveys of cross-sectional profiles in the headcut and channelized parts of the gully. Rainfall excess from a contributing catchment was calculated with the Water Erosion Prediction Project (WEPP) model for all storm events and validated on channel flow measurements. Twelve significant runoff events with hydraulic shear stresses higher than the critical value were identified to potentially cause soil erosion in three out of fourteen survey periods. Analysis of shear stress imposed by peak channel flow on soil surface, antecedent soil moisture condition, and channel shape at individual events provided the basis on which to extend the definition of the critical shear stress function by incorporating the intra-storm changes in soil moisture content. One potential form of this function was suggested and tested with collected data. Similar field studies in other agriculturally-dominated areas and laboratory experiments can develop datasets for a better understanding of the physical mechanisms associated with ephemeral gully progression. Full article
(This article belongs to the Special Issue Streambank Erosion: Monitoring, Modeling and Management)
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Open AccessFeature PaperArticle Watershed Variability in Streambank Erodibility and Implications for Erosion Prediction
Water 2017, 9(8), 605; https://doi.org/10.3390/w9080605
Received: 15 June 2017 / Revised: 8 August 2017 / Accepted: 11 August 2017 / Published: 15 August 2017
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Abstract
Two fluvial erosion models are commonly used to simulate the erosion rate of cohesive soils: the empirical excess shear stress model and the mechanistic Wilson model. Both models include two soil parameters, the critical shear stress (τc) and the erodibility
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Two fluvial erosion models are commonly used to simulate the erosion rate of cohesive soils: the empirical excess shear stress model and the mechanistic Wilson model. Both models include two soil parameters, the critical shear stress (τc) and the erodibility coefficient (kd) for the excess shear stress model and b0 and b1 for the Wilson model. Jet erosion tests (JETs) allow for in-situ determination of these parameters. JETs were completed at numerous sites along two streams in each the Illinois River and Fort Cobb Reservoir watersheds. The objectives were to use JET results from these streambank tests to investigate variability of erodibility parameters on the watershed scale and investigate longitudinal trends in streambank erodibility. The research also determined the impact of this variability on lateral retreat predicted by a process-based model using both the excess shear stress model and the Wilson model. Parameters derived from JETs were incorporated into a one-dimensional process-based model to simulate bank retreat for one stream in each watershed. Erodibility parameters varied by two to five and one to two orders of magnitude in the Illinois River watershed and Fort Cobb Reservoir watershed, respectively. Less variation was observed in predicted retreat by a process-based model compared to the input erodibility parameters. Uncalibrated erodibility parameters and simplified applied shear stress estimates failed to match observed lateral retreats suggesting the need for model calibration and/or advanced flow modeling. Full article
(This article belongs to the Special Issue Streambank Erosion: Monitoring, Modeling and Management)
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