Flow and Sediment‐Transport Modeling

Nelson, Jonathan M.; Bennett, James P.; Wiele, Stephen M.

doi:10.1002/0470868333.ch18

Cited by 85 publications

(111 citation statements)

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“…Turbulence is modeled using the concept of an eddy viscosity, which is calculated in both the vertical and horizontal directions (see Nelson et al, 2003, for a detailed description of the theory and reasoning behind using an eddy viscosity concept in twodimensional flow modeling). The vertical eddy viscosity is assumed to be parabolic for the lower 20% of the flow depth and constant for the upper portion of the water column, resulting in a velocity profile that is logarithmic near the bottom and parabolic well away from the bed.…”

Section: Overview Of Approachmentioning

confidence: 99%

Modeling the influence of flow on invertebrate drift across spatial scales using a 2D hydraulic model and a 1D population model

Anderson

Harrison

Nisbet

et al. 2013

Ecological Modelling

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a b s t r a c tMethods for creating explicit links in environmental flow assessments between changes in physical habitat and the availability and delivery rate of macroinvertebrates that comprise fish diets are generally lacking. Here, we present a hybrid modelling approach to simulate the spatial dynamics of macroinvertebrates in a section of the Merced River in central California, re-engineered to improve the viability of Chinook salmon. Our efforts focused on quantifying the influence of the hydrodynamic environment on invertebrate drift dispersal, which is a key input to salmon bioenergetics models. We developed a twodimensional hydrodynamic model that represented flow dynamics well at baseflow and 75% bankfull discharges. Hydraulic predictions from the 2D model were coupled with a particle tracking algorithm to compute drift dispersal, where the settling rates of simulated macroinvertebrates were parameterized from the literature. Using the cross-sectional averaged velocities from the 2D model, we then developed a simpler 1D representation of how dispersal distributions respond to flow variability. These distributions were included in 1D invertebrate population models that represent variability in drift densities over reach scales. Dispersal distributions in the 2D simulation and 1D representation responded strongly to spatial changes in flow. When included in the 1D population model, dispersal responses to flow 'scaled-up' to yield distributions of drifting macroinvertebrates that showed a strong inverse relationship with flow velocity. The strength of the inverse relationship was influenced by model parameters, including the rate at which dispersers settle to the benthos. Finally, we explore how the scale of riffle/pool variability relative to characteristic length scales calculated from the 1D population model can be used to understand drift responses for different settling rates and at different discharges. We show that, under the range of parameter values explored, changes in velocity associated with transitions between riffles and pools produce local changes in drift density of proportional magnitude. This simple result suggests a means for confronting model predictions against field data.

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Section: Overview Of Approachmentioning

confidence: 99%

Modeling the influence of flow on invertebrate drift across spatial scales using a 2D hydraulic model and a 1D population model

Anderson

Harrison

Nisbet

et al. 2013

Ecological Modelling

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“…[22] For each increment of our topographic time series, we used the Flow and Sediment Transport for Morphological Evolution of Channels (FaSTMECH) computational model, developed by the U.S. Geological Survey [Nelson and Smith, 1989b;Nelson and McDonald, 1996;Lisle et al, 2000;Nelson et al, 2003;Barton et al, 2005], to obtain spatially distributed predictions of water surface elevation, flow depth and velocity, and boundary shear stress. This quasi-three-dimensional model consists of two, weakly coupled components.…”

Section: Flow Modelingmentioning

confidence: 99%

Effect of point bar development on the local force balance governing flow in a simple, meandering gravel bed river

2011

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[1] The patterns of depth, velocity, and shear stress that direct a river's morphologic evolution are governed by a balance of forces. Analyzing these forces, associated with pressure gradients, boundary friction, channel curvature, and along-and across-stream changes in fluid momentum driven by bed topography, can yield insight regarding the establishment and maintenance of stable channel forms. This study examined how components of the local force balance changed as a meandering channel evolved from a simple, flat-bedded initial condition to a more complex bar-pool morphology. A numerical flow model, constrained by measurements of velocity and water surface elevation, characterized the flow field for four time periods bracketing two floods. For each time increment, runs were performed for discharges up to bankfull, and individual force balance components were computed from model output. Formation and growth of point bars enhanced topographic steering effects, which were of similar magnitude to the pressure gradient and centrifugal forces. Convective accelerations induced by the bar reduced the cross-stream pressure gradient, intensified flow toward the outer bank, and routed sediment around the upstream end of the bar. Adjustments in the flow field thus served to balance streamwise transport along the inner bank onto the bar and cross-stream transport into the pool. Even in the early stages of bar development, topographically driven spatial gradients in velocity played a significant role in the force balance at flows up to bankfull, altering the orientation of the shear stress and sediment transport to drive bar growth.Citation: Legleiter, C. J., L. R. Harrison, and T. Dunne (2011), Effect of point bar development on the local force balance governing flow in a simple, meandering gravel bed river,

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“…Channels without major resistance structures will exhibit helical flow patterns which are fundamental to initiation and maintenance of bar structures [149][150][151]. Arranged together as a bar unit, pool, riffle, and point bar elements are positioned distinctly in a channel meander bend [136].…”

Section: Applied Geomorphic Processes For Mesohabitat Maintenancementioning

confidence: 99%

“…Classification characteristics adapted from [79]; and example ecological traits/strategies based on species occupancy [32]. [63,136,150]. Moderately shallow (0.20 m).…”

Section: Mesohabitat Units At Low-flow Stagesmentioning

confidence: 99%

“…This classification scheme recognized the fluvial dynamics of a geomorphic bar unit by incorporating the Bar Unit Concept [36]. As a single geomorphic unit consisting of pool-riffle-bar morphology, the fluvial dynamics is characterized by a 3D convergent-divergent helical flow pattern [147,149,150,153]. In riffles during low flow, downstream-directed velocities accelerate slightly from the reduced water depth, and turbulence is moderate in relative comparison to high TKE observed in the front of pool [152,156].…”

Section: Submerged Barmentioning

confidence: 99%

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Use of Ecohydraulic-Based Mesohabitat Classification and Fish Species Traits for Stream Restoration Design

Schwartz

2016

Water

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Stream restoration practice typically relies on a geomorphological design approach in which the integration of ecological criteria is limited and generally qualitative, although the most commonly stated project objective is to restore biological integrity by enhancing habitat and water quality. Restoration has achieved mixed results in terms of ecological successes and it is evident that improved methodologies for assessment and design are needed. A design approach is suggested for mesohabitat restoration based on a review and integration of fundamental processes associated with: (1) lotic ecological concepts; (2) applied geomorphic processes for mesohabitat self-maintenance; (3) multidimensional hydraulics and habitat suitability modeling; (4) species functional traits correlated with fish mesohabitat use; and (5) multi-stage ecohydraulics-based mesohabitat classification. Classification of mesohabitat units demonstrated in this article were based on fish preferences specifically linked to functional trait strategies (i.e., feeding resting, evasion, spawning, and flow refugia), recognizing that habitat preferences shift by season and flow stage. A multi-stage classification scheme developed under this premise provides the basic "building blocks" for ecological design criteria for stream restoration. The scheme was developed for Midwest US prairie streams, but the conceptual framework for mesohabitat classification and functional traits analysis can be applied to other ecoregions.

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Flow and Sediment‐Transport Modeling

Cited by 85 publications

References 0 publications

Modeling the influence of flow on invertebrate drift across spatial scales using a 2D hydraulic model and a 1D population model

Modeling the influence of flow on invertebrate drift across spatial scales using a 2D hydraulic model and a 1D population model

Effect of point bar development on the local force balance governing flow in a simple, meandering gravel bed river

Use of Ecohydraulic-Based Mesohabitat Classification and Fish Species Traits for Stream Restoration Design

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