Advances in assessing the mechanical and hydrologic effects of riparian vegetation on streambank stability

Pollen, Natasha; Simon, Andrew; Collison, Andrew

doi:10.1029/008wsa10

Cited by 91 publications

(99 citation statements)

References 22 publications

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“…Since the 1960s, specific methods of bank stability analysis have been progressively disseminated, with an increasing effort to define closed-form solutions for planar failures representative of characteristic bank geometries (Table 9.1). It is evident that research has progressively sought to account for: (1) a more realistic bank geometry and the influence of tension cracks (Osman and Thorne, 1988); (2) positive pore water pressures and hydrostatic confining pressures (Simon et al, 1991;Darby and Thorne, 1996b); (3) the effects of negative pore water pressures in the unsaturated part of the bank Casagli et al, 1999;Simon et al, 2000); and (4) the influence of riparian vegetation (Abernethy and Rutherfurd, 1998Simon and Collison, 2002;Rutherfurd and Grove, 2004;Pollen et al, 2004;Van de Wiel and Darby, 2004;Pollen and Simon, 2005;Pollen, 2006). Recently, more complex analyses have been utilised for river bank studies (Abernethy and Rutherfurd, 2000;Dapporto et al, 2001Rinaldi et al, 2004) by using various LEM solutions extended to rotational slides (i.e., Bishop, Fellenius, Jambu, Morgestern, GLE) that include features that overcome many of the previous limitations.…”

Section: Methods Of Analysismentioning

confidence: 99%

“…Considering the mechanical effects of vegetation first, the net effect of vegetative surcharge can be either beneficial (increase in normal stress and therefore in the frictional component of soil shear strength) or detrimental (increasing the downslope component of gravitational force), depending on such factors as the position of the tree on the bank, the slope of the shear surface, and the friction angle of the soil (Gray, 1978;Selby, 1982). However, the most important mechanical effect that vegetation has on slope stability is the increase in soil strength induced by the presence of the root system, and considerable progress has recently been made in quantifying this effect (Gray, 1978;Wu et al, 1979;Greenway, 1987;Gray and Barker, 2004;Pollen et al, 2004;Pollen and Simon, 2005;Pollen, 2006). Surcharge and root reinforcement have been recently included in bank stability models (Abernethy and Rutherfurd, 1998Simon and Collison, 2002;Van de Wiel and Darby, 2004;Rutherfurd and Grove, 2004;Pollen and Simon, 2005;Pollen, 2006).…”

Section: Effects Of Vegetationmentioning

confidence: 99%

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9 Modelling river-bank-erosion processes and mass failure mechanisms: progress towards fully coupled simulations

Rinaldi¹,

Darby²

2007

Developments in Earth Surface Processes

125

118

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This paper reviews recent developments in modelling the two main sets of bankerosion processes and mechanisms, namely fluvial erosion and mass failure, before suggesting an avenue for research to make further progress in the future. Our review of mass failure mechanisms reveals that the traditional use of limit equilibrium methods to analyse bank stability has in recent years been supplemented by research that has made progress in understanding and modelling the role of positive and negative pore water pressures, confining river pressures, and hydrograph characteristics. While understanding of both fluvial erosion and mass failure processes has improved in recent years, we identify a key limitation in that few studies have examined the nature of the interaction between these processes. We argue that such interactions are likely to be important in gravel-bed rivers and present new simulations in which fluvial erosion, pore water pressure, and limit equilibrium stability models are combined into a fully coupled analysis. The results suggest that existing conceptual models, which describe how bank materials are delivered to the fluvial sediment transfer system, may need to be revised to account for the unforeseen effects introduced by feedback between the interacting processes.

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Section: Methods Of Analysismentioning

confidence: 99%

Section: Effects Of Vegetationmentioning

confidence: 99%

9 Modelling river-bank-erosion processes and mass failure mechanisms: progress towards fully coupled simulations

Rinaldi¹,

Darby²

2007

Developments in Earth Surface Processes

125

118

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“…We observed similar spatial and temporal variability at the plot and basin scale. While mechanistic processes controlling bank erosion at individual sites have been well documented (e.g., Lawler, 1992;Simon and Collison, 2002;Pollen et al, 2004;Fox et al, 2007), understanding the distribution of variable bank erosion processes operating at the basin scale lags behind. For example, Lawler et al (1999) interpreted the variability within individual eroding plots in the Swale Ouse river system as an indication of erosional processes and the variability among plots as an indication of longitudinal changes in the erosion process at the basin scale.…”

Section: Recession Datamentioning

confidence: 99%

“…Much work has been focused on the driving mechanistic forces of bank erosion on individual sites (e.g., Simon et al, 1999;Simon and Collison, 2002;Pollen et al, 2004;Fox et al, 2007) with far fewer studies examining how bank erosion processes impact sediment loading dynamics at a larger spatial scale. For example, Couper (2004) identified 66 bank erosion studies conducted from 1959 to 2003 and reported that 59 of them focused at the site or reach scale and seven studies focused at the catchment scale.…”

Section: Introductionmentioning

confidence: 99%

Streambank erosion rates and loads within a single watershed: Bridging the gap between temporal and spatial scales

et al. 2014

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The importance of streambank erosion to watershed-scale sediment export is being increasingly recognized. However few studies have quantified bank erosion and watershed sediment flux at the basin scale across temporal and spatial scales. In this study we evaluated the spatial distribution, extent, and temporal frequency of bank erosion in the 5218 ha Walnut Creek watershed in Iowa across a seven year period. We inventoried severely eroding streambanks along over 10 km of stream and monitored erosion pins at 20 sites within the watershed. Annual streambank recession rates ranged from 0.6 cm/yr during years of hydrological inactivity to 28.2 cm/yr during seasons with high discharge rates, with an overall average of 18.8 cm/yr. The percentage of total basin export attributed to streambank erosion along the main stem of Walnut Creek ranged from 23 to 53%. Large variations in individual site, annual rates and percentage of annual load suggested that developing direct relationships between streambank erosion rates and total sediment discharge may be confounded by the timing and magnitude of discharge events, storage of sediments within channel system and the remobilization of eroded material. RightsWorks produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted. The importance of streambank erosion to watershed-scale sediment export is being increasingly recognized. However few studies have quantified bank erosion and watershed sediment flux at the basin scale across temporal and spatial scales. In this study we evaluated the spatial distribution, extent, and temporal frequency of bank erosion in the 5218 ha Walnut Creek watershed in Iowa across a seven year period. We inventoried severely eroding streambanks along over 10 km of stream and monitored erosion pins at 20 sites within the watershed. Annual streambank recession rates ranged from 0.6 cm/yr during years of hydrological inactivity to 28.2 cm/yr during seasons with high discharge rates, with an overall average of 18.8 cm/yr. The percentage of total basin export attributed to streambank erosion along the main stem of Walnut Creek ranged from 23 to 53%. Large variations in individual site, annual rates and percentage of annual load suggested that developing direct relationships between streambank erosion rates and total sediment discharge may be confounded by the timing and magnitude of discharge events, storage of sediments within channel system and the remobilization of eroded material.

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“…An early relationship describing increased soil strength due to roots is a function of root tensile strength, areal density, and root distortion during shear (Wu et al, 1979). This equation tends to overestimate root reinforcement because it assumes that all roots contribute their full tensile strength during failure and that all roots break simultaneously (Pollen and Simon, 2005;Pollen et al, 2004) . To correct this, a new algorithm, RipRoot, was developed (Pollen and Simon, 2005).…”

Section: A1 Bstem Summarymentioning

confidence: 99%

Uncertainty and sensitivity in a bank stability model: implications for estimating phosphorus loading

Lammers

Bledsoe

Langendoen

2016

Earth Surf Processes Landf

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UNCERTAINTY AND SENSITIVITY IN A BANK STABILITY MODEL: IMPLICATIONS FOR ESTIMATING PHOSPHORUS LOADINGEutrophication of aquatic ecosystems is one of the most pressing water quality concerns in the U.S. and around the world. Bank erosion has been largely overlooked as a source of nutrient loading, despite field studies demonstrating that this source can account for the majority of the total phosphorus budget of a watershed. Substantial effort has been made to develop mechanistic models to predict bank erosion and instability in stream systems; however, these models do not account for inherent natural variability in input values. Providing only single output values with no quantification of associated uncertainty can complicate management decisions focused on reducing bank erosion and nutrient loading to streams. To address this issue, uncertainty and sensitivity analyses were performed on the Bank Stability and Toe Erosion Model (BSTEM), a mechanistic model developed by the USDA-ARS that simulates both mass wasting (stability) and fluvial erosion of streambanks. Sensitivity analysis results indicate that variable influence on model output can vary depending on assumed input distributions.Generally, bank height, soil cohesion, and plant species were found to be most influential in determining stability of clay (cohesive) banks. In addition to these three inputs, groundwater elevation, stream stage, and bank angle were also identified as important in sand (non-cohesive) banks. Slope and bank height are the dominant variables in fluvial erosion modeling, while erodibility and critical shear stress are relatively unimportant. However, the threshold effect of critical shear stress (determining whether erosion occurs) was not explicitly accounted for, ii possibly explaining the relatively low sensitivity indices for this variable. Model output distributions of sediment and phosphorus loading rates corresponded well to ranges published in the literature, helping validate both model performance and selected ranges of input values. In addition, a probabilistic modeling approach was applied to data from a watershed-scale sediment and phosphorus loading study on the Missisquoi River, Vermont to quantify uncertainty associated with these published results. While our estimates indicated that bank erosion was likely a significant source of sediment and phosphorus to the watershed in question, the uncertainty associated with these predictions indicates that they should probably be considered order of magnitude estimates only.iii ACKNOWLEDGEMENTS

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Advances in assessing the mechanical and hydrologic effects of riparian vegetation on streambank stability

Cited by 91 publications

References 22 publications

9 Modelling river-bank-erosion processes and mass failure mechanisms: progress towards fully coupled simulations

9 Modelling river-bank-erosion processes and mass failure mechanisms: progress towards fully coupled simulations

Streambank erosion rates and loads within a single watershed: Bridging the gap between temporal and spatial scales

Uncertainty and sensitivity in a bank stability model: implications for estimating phosphorus loading

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