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Graduate Research Assistants of Dr. John S. Schwartz
     
Current Graduate Students
 

Siavash Hoomehr

Patrick McMahon

Chris Rolinson

Tim Pobst

Tony Celebucki

Jeremy Mefford

 
     
Former Graduate Students
 

J. Brady McPherson

G. Tom Zimmerman

Keil J. Neff

J. Lee Mauney

Mary Ann Grell

Meijun Cai

William Cantrell

Joseph Parker

Daniel Johnson

Patrick Massey
Tara Mallison
Edwin Deyton
Dan Carter
Robert Sain
Frank Dworak

Kelley Williams

Shannon Bennett

Brantley Thames

Chris Howley

Angela Brawley

 

Current Graduate Students


 

Siavash Hoomehr

Ph.D. Candidate -- Civil Engineering

M.S. Water Engineering -- University of Tehran, Iran 2007

B.S. Civil Engineering -- Shiraz University, Iran 2003

email: shoomehr@utk.edu

website: http://web.utk.edu/~shoomehr/


Research: Sediment delivery and erosion control.

I am working on a project funded by the Office of Surface Mining, which is also shared with the University of Tennessee Forestry Department. On the engineering side, the project consists of engineering stable slopes on reclaimed surface mine lands and understanding hydrological changes and erosion conditions as vegetation re-growth occurs over time.

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Chris Rolison

M.S. Candidate -- Environmental Engineering - Water Resources

B.S. Civil Engineering -- University of Tennessee 2008


crolison@utk.edu

 

Research: Water quality of the Noland Divide Water Shed

 

Thesis: Effects of Elevation on Soil Nitrification

 

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Patrick Lasater McMahon

Ph.D. Candidate -- Civil Engineering - Water Resources

Licensed Civil Engineer in Tennessee and Alaska


pmcmahon@utk.edu

 

M.S. Environmental Engineering (Water Resources) -- University of Tennessee 2005

B.S. Civil Engineering-- University of Tennessee 2003


Research: Stream restoration, sediment transport, sediment and hydraulic modeling.

 

Geomorphic success of stream restoration projects is largely dependent on reach-scale hydraulic geometry that provides a long-term balance between bed-material sediment supply and transport capacity.  In gravel-bed streams with changing land use conditions, obtaining this balance is often the most difficult aspect of restoration design.  Patrick's research focuses on improving the restoration design process by evaluating practical solutions for assessment of sediment supply and transport capacity relations. Outcomes of the project will provide design practitioners detailed guidelines for estimating bed material transport.

 

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Former Graduate Students



 

Lee Mauney

M.S. Candidate -- Environmental Engineering

B.S. Civil Engineering -- University of Tennessee 2008

lee.mauney@gmail.com

 

Field blog: http://nolanddivide.blogspot.com/

Website: http://web.utk.edu/~mauney01

Research Interests: Water quality, hydraulic modeling, atmospheric deposition, hydrology, GIS, stochastic hydrology. 

Thesis: Stochastic Analysis of Episodic pH Events

Continuously monitored pH data allow for construction of concentration-duration-frequency (CFD) curves that provide time-connected durations and frequencies of episodic events. These CFD curves produce characteristic equations that can be compared with physical GIS attributes for a specific watershed.  Applying this methodology to multiple stream sites within the GRSM can serve to conceptualize pH responses in unique watersheds to answer stochastic and risk analysis questions.  In particular, outcomes of a multi-site study using CFD curves may provide a means to parameterize the episodic nature of acidifications and relate findings to brook trout impairment in the park.

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Mary Ann Grell

M.S. Candidate - Environmental Engineeering

B.S. Civil Engineering -- University of Tennessee 2008

mgrell@utk.edu

Research: Watershed physical parameters impacting water and soil chemistry, GIS modeling.

The Great Smoky Mountains National Park has endured decades of atmospheric acidic deposition, and despite recent regulatory policies decreasing deposition rates, ecosystem recovery has been minimal.  My research involves comparing physical and chemical properties of the dominant soil types found in eight watersheds considered to be acid sensitive.  The objective is to determine how these soil properties differ between watersheds and how factors such as topography and geology influence soil chemistries.  Extensive research has also been done regarding water chemistry in these same watersheds.  Correlations between soil chemistry and stream acidification may also be determined from this study and data will support the development of a biogeochemical model.

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Tom Zimmerman

M.S. candidate -- Environmental Engineering

B.S. Civil Engineering - University of Tennessee

 

g.t.zimmerman@gmail.com

 

Research: Hydraulic modeling, water chemistry.
 

Episodic acidification of surface waters is a concern in the Great Smoky Mountain National Park due to deleterious affects on water quality and aquatic biota.  The high elevation areas of the Great Smoky Mountains experience significant acidification through several processes including dry deposition, cloud water deposition, increased orographic acid rain, poor buffering capacity, base cation dilution, organic acids flux, and geologic weathering. Additionally, some processes dominate during baseflow conditions, while others dominate during stormflow discharges.  Deyton 2007 showed that episodic acidification was most severe during stormflow that was preceded by dry days, and the dominant mechanism of acidification varied spatially at three different sites within the Middle Prong of the Little Pigeon watershed.  Neff 2007 demonstrated that native brook trout exhibited adverse physiological stress during episodic acidification at these same three sites.  My current research builds on the work of Deyton 2007 and Neff 2007 by performing a mass balance and modeling the mass transport of ions during stormflow and baseflow.  The computer software River2D will be used to model various flows at the three sites.  The discharge will be measured for a several varying flows using a velocity flow meter at cross sections for each site to calculate a volumetric discharge, and this will be used to calibrate the River2D model.  The stage will then be correlated to discharge, giving a stage-discharge relationship that can be coupled with the existing chemistry data to determine mass loadings in the stream.  The stream will then be modeled at various stages for a mass balance of the ions, and stormflow and baseflow mass transport will be compared.

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The development of regional relationships among stream flow, channel morphology, valley morphology, and basin characteristics using existing network of USGS gage stations is the main objective.  The outcome of regional curve relationships among stream flow, channel morphology, valley morphology, and basin characteristics will be a family of hydraulic relationship curves for the Ridge and Valley Physiographic Province.  The following hydraulic relationships will be determined: Bankfull discharge and drainage area; bankfull stream dimensions (width, depth, cross-sectional area at bankfull stage) and drainage area; relative roughness and total channel hydraulic resistance; and flood return intervals.
The second objective is the development of a stream channel reference condition design database for the Ridge and Valley Physiographic province. A network of stream channel reference sites across the physiographic province, classified by valley type and stream type, will provide baseline fluvial geomorphic attributes (stream dimension, profile, and pattern) as well as channel stability and habitat condition.  This work will be compared to the regional curves developed in the Ridge and Valley regions of Virginia, Maryland, and West Virginia (USGS, 2005). 

J. Brady McPherson

M.S. candidate -- Environmental Engineering

B.S. Biology; Plant and Soil Science - Middle Tennessee State Univesity 2009

 

jmcpher6@utk.edu

 

Research: Stream restoration, regional curves.
 


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Meijun Cai

Ph.D. candidate
Civil Engineering
-- Environmental - Water Quality

 

mcai@utk.edu


B.S. Environmental Engineering -- East China University of Science and Technology 1997
M.S. Environmental Engineering -- East China University of Science and Technology 2000
M.S. Environmental Engineering -- Technical University of Denmark 2006

 

Research: Water qualilty, soil chemistry.



My current research interests involve studying the response of soil solution and stream chemistry in the Noland Divide Watershed to the long-term acidic deposition.  I have investigated the possible hydrochemical processes inside this watershed by analyzing the change of flux and concentrations for sulfate, nitrogen (ammonium and nitrate), proton and base cations from deposition, to soil solution and finally stream export. In addition, the temporal trend of sulfate and nitrogen flux and concentration since 1991 were studied. I am presently characterizing the soil chemical compositions through soil extraction, incubation and digestion experiments. Moreover, several column leaching experiments and one field experiment are being used to predict the stream chemistry subject to the future deposition scenarios.

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Keil J. Neff

Ph.D.. Candidate
Civil Engineering - Water Resources


kjn.water@gmail.com

 

M.S. Environmental Engineering (Water Resources) -- University of Tennessee 2007

B.S. Engineering Science/ Anthropology -- Vanderbilt University 1997


Research: Water quality, aquatic toxicology, stream restoration, hydraulic modeling, watershed hydrology, GIS modeling.

 

Curricullum Vita

Website: http://web.utk.edu/~kneff1/

 

THESIS: Physiological Stress in Native Brook Trout (Salvelinus Fontinalis) During Episodic Acidification of Streams in the Great Smoky Mountains National Park

 

"Listen to the river sing sweet songs, to rock my soul." - Robert Hunter, 1970

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William Cantrell

M.S. Environmental Engineering -- Univesity of Tennessee 2009

B.S. Civil Engineering -- Univesity of Tennessee 2007


wcantrel@tennessee.edu


Research: Sediment modeling, watershed hydrology, stream restoration.

 

A central problem in the field of stream restoration is that of designing a stable channel that supports a healthy benthic population.  Many stream restoration projects take place in urban or urbanizing watersheds.  The relationship between changing watershed characteristics and local channel conditions within that watershed is poorly understood.  This study is made up of two major components that address aspects of this problem: first, a physical study of bedload flux in watersheds representing rural, urban, and developing conditions and second, verification of results from the Computational Hydraulic Engineering Two-Dimensional Sediment Model (CCHE2D) on the reach scale and correlation of CCHE2D results with Rapid Bioassessment Protocol III (RBP III) scores.  Study sites were selected in Knox County, Tennessee including twelve sites for the bedload study and a single site for the CCHE2D model verification.  The bedload flux portion of the study combines field collection of bedload via Bunte bedload net traps (Bunte et al., 2004) and estimate of energy slope with peak stage recorders.  Information derived from the field collection will be combined with watershed data via geographic information system (GIS) analysis.  Watershed metrics including percent impervious area, roadways adjacent to streams, and average watershed slope determined via GIS will be correlated with the measured bedload mass and composition for each research site.  The CCHE2D model verification will combine the study of bedload flux with a previous study correlating the surficial bed material composition with macroinvertebrate biotic integrity scores (RPB III) for 76 reaches in East Tennessee (Williams, K., unpublished thesis, 2005).  The combination of this information will provide a valuable tool in stream restoration design in allowing practitioners to have an empirical metric with which to design/predict channel substrate composition as an indicator of physical habitat quality.

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Joseph Parker

M.S. Environmental Engineering -- University of Tennessee 2008

B.S. Civil Engineering -- Christian Brothers University 2007

jparke33@utk.edu

Research: Hydrology modeling, GIS modeling, ecological hydrology.

 

THESIS: The Influence of Natural Hydrological Disturbances on Brook Trout (Salvelinus fontinalis) Population Dynamics in the Great Smoky Mountains National Park.

My research focuses on how hydrological processes impact the functioning of ecosystems and influence fish population dynamics.  The flow regime of a stream affects the structure, composition, and productivity of fish communities by regulating abiotic habitat conditions and biotic processes.  In the Great Smoky Mountains National Park (GRSM), native brook trout (Salvelinus fontinalis) populations have declined in some watersheds over the past decade.  To evaluate the impact of hydrological disturbances on trout, I computed indicators of hydrologic alteration (IHA) for a select number of the total fish sampling sites between 1990 and 2007.  Because fish sites were located in ungaged watersheds, the Hydrological Simulation Program - FORTRAN (HSPF) was used to model flows.  I calibrated the model by adjusting parameters including storage, infiltration, runoff, and ground water for three elevation classes (low < 800 m ≤ medium < 1200 m ≤ high) to fit flow output from model with two USGS gaging stations and one NPS gaging station.  Hydrological alteration was defined by a) magnitude, b) frequency, c) duration, d) time, and e) rate of change for 1) extreme low flow, 2) low flow, 3) high flow pulse, 4) small floods, and 5) large floods.  The ecohydrologic regimes, characterized using the IHA method, were compared with trout abundance and biomass at each site.  Preliminary results indicate extreme flood conditions significantly lowered young of year (YOY) trout abundance.  Low flow (drought) conditions reduced fish biomass and was highly correlated with lower abundance and biomass of brook trout.  These impacts were most pronounced in low elevation streams, which provide less temperature refugia and increased competition from rainbow trout.  Brook trout repopulated stream reaches in 2-3 years following low flow regimes.  This study provides a valuable tool to watershed managers and fishery biologists of the GRSM to understand the effects of hydrologic disturbances on trout population dynamics, and contributes a unique hydrology model for GRSM watersheds to be used for future research.

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Daniel Johnson

M.S. Environmental Engineering -- University of Tennessee 2008
B.S. Civil Engineering -- Clemson University 2005


djohnson@coastalscience.com
or djohnson.ei@gmail.com

Research: Sediment modeling, stream restoration.


THESIS: The application of a two-dimensional sediment transport model in a Cumberland Plateau mountainous stream reach with complex morphology and coarse substrate

A successful stream restoration project depends on accurate prediction of sediment transport. To facilitate the design process, numerical models have been developed to quantify in-stream sediment transport and hydraulic characteristics, and multiple sampling techniques have been proposed to establish the upstream sediment supply. However, the governing physical boundaries and variables (i.e., Manning’s ‘n’ variable, energy slope, and upstream sediment supply) required to initiate a sediment transport simulation are difficult and expensive to measure, and estimations of these variables can lead to inaccurate predictions of sediment transport, resulting in the design of unstable projects.

The goal of this study was to evaluate the performance of CCHE2D, a 2D sediment transport model, in a Cumberland Plateau mountainous stream reach with complex morphology and coarse substrate. The model was utilized to simulate sediment transport through a single hydrograph. Bed elevation change along a reach (100-m scale), was evaluated by comparing the deviation between simulated and measured elevations at multiple monitoring points before and after a flood event. The study objective included testing the sensitivity of overall bed change to Manning’s n values and sediment supply. Despite the relative stability observed along the site, simulated results show the model overestimated aggradation at reach, local, and point scales. Results demonstrated bed elevation change was sensitive to the bedload rating curve and Manning’s n value input parameters. Importantly, site-specific bedload rating curves and measured roughness coefficients have the potential to reduce the error between simulated and measured results and produce accurate simulations of sediment transport in computational models.

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Patrick Massey

M.S. Environmental Engineering -- University of Tennessee 2008
B.S. Civil Engineering -- University of Tennessee 2006

PatrickMassey@kub.org

mpmassey3@gmail.com

Research interests: Sediment modeling, forest hydrology, water and wastewater utilities.


THESIS: Use of the AnnAGNPS pollutant loading model for prediction of sediment yields in a mountainous Cumberland Plateau region: correlations with the stream bed sediment characteristics

 

This study attempts to develop a relationship with the hillslope sediment yield (estimated from a computer model) and the deposited sediment particle size characteristics within stream channels. By using specific hydrological parameters within a watershed, a calibrated Annualized Agricultural Non-Point Source (AnnAGNPS) pollutant loading model was created for four different sub-watersheds in the mountainous New River Basin of eastern Tennessee. The AnnAGNPS pollutant loading model predicted daily runoff and sediment yield reasonably well, but it poorly predicted daily peak flow rate for most sub-watersheds analyzed in the New River Basin. Overall, the AnnAGNPS pollutant loading model provided satisfactory results in a mountainous, nonagricultural landscape with a limited amount of climatic data available. The average annual hillslope sediment yield, in terms of clays, silts, and sands, was calculated with the AnnAGNPS model for years 2006 and 2007, to compare with sediment deposition characteristics in the streams.

The fine particle size characteristics collected at specific bed deposition points were suspected to have a strong correlation with predicted sediment yield output from a calibrated AnnAGNPS pollutant loading model. The sites of the captured sediment were at locations just downstream of specific land use disturbances such as dirt roads, surface mining, and forest logging, all of which can be detrimental to the health of a stream environment and habitat if disturbances are not properly managed. In this study, the sediment collected at the channel bed deposition points represented the distribution of different material sizes that have recently moved within the stream during large discharge events.
This investigation concluded that the certain measurements of the clays, silts, sands, and gravel material found in downstream sediment depositional points had a variety of significant relationships (p-value < 0.05) with the clays, silts, sands, and total sediment yield occurring on the watershed hillslopes. Overall, there are a limited amount of studies that analyze these collections of fine sediment deposited in areas of the stream that have interrupted velocity forces due to channel shape, objects, or formations. This study showed that the use of the AnnAGNPS pollutant loading model and the analyzation of specific fine sediment at depositional points in the stream, proper watershed management of a rural mountainous region can be better established.

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Tara Mallison

M.S. Environmental Engineering -- University of Tennessee 2007
B.S. Civil Engineering -- Auburn 2006


tara.mallison@ch2m..com

THESIS: Comparing In Situ Submerged Jet Test Device and Laboratory Flume Methods to Estimate Erosional Properties of Cohesive Soils for Bank Stability Models

In order to accurately predict the stability of riverbanks, model input parameters must be reliable bank failure estimators. Currently, bank stability models require two input parameters to predict bank erosion: critical erosion shear stress and erodibility coefficient. The investigation’s purpose was to compare two erosion estimation methods and improve the bank stability models for cohesive soil commonly found on the banks.
To accomplish the objective, critical shear stresses and erodibility coefficients obtained using the in situ submerged jet test device (SJT) were measured against results from the closed-loop laboratory flume method for 12 cohesive bank sites. Additionally, SJT critical shear stress values were compared to values found via empirical relationships found in literature that incorporate plasticity index, median particle diameter, percent siltclay or percent clay content to compute critical shear stress. Particle size analysis and Atterberg limit determinations were run classify the sediment type collected. The critical shear stress values obtained ranged from 0.09 to 5.84 Pa and SJT erodibility coefficients varied from 0.37 to 10.07 cm3/N·s. From flume observations, cohesive soil erosion was influenced by interparticle forces and occurred in aggregate pieces and particle-by-particle. A few critical shear stress values appeared to be unreliable considering the critical shear stress threshold of 1.83 Pa found using the laboratory flume analysis and the limited erosion witnessed. Study results also indicated that sediment properties did not correlate directly with the SJT critical shear stress values or with each other.


 

Flume observations and variations among experimental results suggest other influential factors exist besides critical shear stress and the erodibility coefficient when quantifying the cohesive sediment erosivity. When empirical results were lower than the flume’s critical shear stress threshold, it was possible the mechanical soil property could not be transferred to the soil types tested or estimates incorrectly assumed zero physical and chemical influences. Because of its complexities, traditional experimental design may not reliably measure cohesive soil erosion. Only through the continued collaboration of various field and advanced degree professionals and the detailed, high-quality documentation of as many influential parameters as possible per project can the goal of estimating cohesive sediment erosion be accomplished.

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Edwin Deyton

M.S. Environmental Engineering -- University of Tennessee 2007
B.S. Civil Engineering -- University of Tennessee 2006

ebdeyton@vaughnmelton.com

edeyton@gmail.com

THESIS: Characterizing Episodic Stream Acidity During Stormflow in the Great Smoky Mountains National Park


Episodic stream acidification occurs as storm events temporarily reduce acid neutralizing capacity (ANC) and pH. Stream acidification is suspected to have damaging effects on the health of aquatic ecosystems and biota. The objectives of this research are to 1) characterize stream baseflow and stormflow chemistries in three watersheds in the Great Smoky Mountains National Park (GRSM), 2) understand potential mechanisms responsible for episodic acidification, and 3) understand the relationship between storm event magnitude, antecedent soil moisture condition, and the stream’s pH response. Three remote, forested, high-elevation streams (Middle Prong, Ramsey Prong, and Eagle Rocks Prong) were selected in the Middle Prong of the Little Pigeon River Watershed. Multi-parameter data sondes were installed at each site to record continuous stream data. Autosamplers were set up in connection with the sondes to collect samples during storm events. Stormflow, baseflow, and precipitation samples were analyzed for pH, ANC, and a broad spectrum of cations and anions that contribute to the ion balance.
During stormflow, ANC and pH depressions were observed for all storms at each study site. Sulfate, nitrate, and organic acid concentrations increased during each storm. Base cation concentrations generally increased during stormflow at Middle and Ramsey Prongs, but diluted occasionally on Eagle Rocks Prong. The relative changes in ion concentrations were used to determine which ions (acids) were most responsible for ANC depression. ANC contribution analysis indicates acid deposition may be the primary cause of episodic acidification, but it appears organic acids and cation dilution may also contribute. Pyritic geology is also suspected to contribute to baseflow and stormflow acidity in the Eagle Rocks Prong. Data exploration indicates large storms preceded by long, dry periods cause the largest pH depressions. It appears stream acidification may be driven by acid deposition, but additional inputs from varying vegetation and geology create unique and complex response to the observed stream acidification.

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Dan Carter

M.S. Environmental Engineering -- University of Tennessee 2007
B.S. Civil Engineering -- University of Tennessee 2005


whodancarter@gmail.com

THESIS: Stream Restoration Assessment of Abrams Creek in the Great Smoky Mountains National Park: Management Implications and Comparison of Empirical and Analytical Physical Assessment Approaches


Natural resource managers in the Great Smoky Mountains National Park requested the assistance of the University of Tennessee Department of Civil and Environmental Engineering to assess Abrams Creek for potential stream restoration needs. A presumed, unstable study reach and a stable reference reach were identified on Abrams Creek in Cades Cove. Chemical, biological and physical assessments were completed on Abrams Creek in order to evaluate ecological health and channel stability of the stream. Water quality and ecological (fish and habitat surveys) data acquired by National Park Service, Tennessee Valley Authority and the University of Tennessee were assessed. The physical assessment included two approaches; they were: 1) empirical or reference reach approach; and 2) analytical or non-reference reach approach. The current empirical technique used was the analog Natural Channel Design. The current analytical techniques were the hydraulic, sediment transport and erosion models (HEC-RAS, CONCEPTS). These physical assessment techniques were used to determine bankfull or effective flows, sedimentation, stream stability, and ecohydraulics. In addition to using these techniques for the Park’s management objectives, they were applied to both reaches for comparison in order to clarify areas where professional judgment may introduce uncertainty. From comprehensive physical assessments no system wide instabilities were observed but some riparian area differences and localized erosion were noted. Recommendations for potential restoration needs on Abrams Creek include localized stabilization of stream banks and vegetating the riparian corridor along the study reach.

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Robert Sain

M.S. Biosystems Engineering Technology -- University of Tennessee 2006

rlsain@mactac.com

robertsain@gmail.com

Research interests: Stream restoration.


THESIS: Characterizing how fish communities and physical habitat structure are affected by urbanization in an East Tennessee watershed.

 

Urbanization alters watershed hydrology, which leads to degradation of physical and biological components of urban streams. A part of this scenario is thought to be a product of increased storm water runoff due to excessive impervious surface. Impervious surface runoff increases the peak discharge in urban streams, causing a flushing or rapid flooding effect to occur. This flushing effect can overwhelm the natural pattern and profile of a stream channel, causing degradation of habitat and the fish population. This study investigates urbanization effects on habitat structure and fish communities in a rapidly urbanizing watershed in East Tennessee.

Field measures of habitat complexity and fish indices of biotic integrity (IBI) were gathered for twenty-four stream reaches in the Beaver Creek watershed, Knox County, Tennessee. Habitat inventory produced 291 Channel Geomorphic Units (CGU) with up to 20 measurements taken in each unit. Average width and depth measurements were performed on 10 different types of pools. IBI sampling produced 7185 fish, yielding 21 species of 7 families in the 24 sites. A combination of Pearson correlations, multiple and simple linear regression, and Analysis of Variance (ANOVA) means separation techniques were used to see if changes in measured habitat and fish metrics occurred in relation to increased urbanization. Potential urbanization effects on physical habitat structure and fish communities were first considered at the (p< .10) significance, using the Pearson correlation technique. Multiple and linear regressions were used to explain the strongest relationships found for fish and habitat, to increase in urbanization (p< 0.05). ANOVA means separation was used to examine and validate relationships found using the six sub-watersheds as treatments, and the four reaches within each sub-watershed as replicates.Mosaics of urban land use varied from 1 to 54% in the watershed catchments. The statistical techniques described earlier were employed to gather relationships found between fish and habitat sites relative to an urbanization gradient. Measures of physical habitat structure were weakly correlated with percent urbanization. As percent urbanization increased, IBI scores decreased (p = 0.0004), and the number of darters decreased (p = 0.0041). Sub-watersheds significantly differed for IBI scores (p = 0.0015), and for curve number values (p = 0.0048).
Results suggest that within the range of urbanization used for this study (1 to 54% total urban and 1 to 18% commercial/ industrial) channel geomorphic units such as scour pools and riffles are not significantly altered. However, fish community assemblages did show a shift towards impairment as quantified by the IBI. This indicates that a stressor other than physical habitat degradation causes a negative effect on fish in the Beaver Creek watershed.

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Frank Dworak

M.S. Environmental Engineering -- University of Tennessee 2005


fdworak@geiconsultants.com


THESIS: Characterizing Turbulence Structure along Woody Vegetated Banks in Incised
Channels: Implications for Stream Restoration


The impacts of urbanization have modified natural watersheds and stream hydraulic, hydrologic, and geomorphic processes that have lead to geomorphic and ecological disturbances in natural stream systems. These alterations have resulted in channel incision and the loss of channel-scale hydraulic characteristics responsible for initiating and maintaining pool-riffle bedforms, which are capable of supporting diverse biological stream ecosystems. Through the use of FLOW-3D, a 3-dimensional computational fluid dynamics model, three scenarios of an urban, incised, and channelized stream were simulated to characterize the turbulent, hydraulic structure during bankfull discharge. The simulations were conducted with trees inhibiting bankfull flow (representing the channel’s current state), trees removed from the channel, and a restoration design using three clusters of the original trees to initiate flow acceleration-deceleration regions. These simulations suggested that hydraulic processes found to initiate and maintain poolriffle sequences can be restored to impaired urbanized channels for which these processes have been lost. This research can be applied to stream restoration design in hopes to establish less invasive procedures that can promote the development and maintenance of natural stream processes. If the natural processes can be restored to the channel, it is likely the project will have a higher degree of success in the future of the stream system.

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Kelley Williams

M.S. Environmental Engineering-- University of Tennessee 2005

THESIS: Linking Channel Stability and Bed Sediment Characteristics to Biological Integrity in Tennessee Ridge and Valley Streams

 

Streambed sedimentation has plagued waterways since the beginning of civilization, whether as a natural flow process or human disturbances on the landscape in more recent times. Due to the continual degradation in the quantity and diversity of aquatic organisms within streams, the issue has finally surfaced as a significant concern. The need to develop better Total Maximum Daily Load (TMDL) assessment tools to link sediment impairment to biological integrity was the driving force behind this study. Within the Ridge and Valley Ecoregion, 76 stream reaches were analyzed to investigate the impacts of stability issues and bed sediment characteristics on stream biological integrity. The field data were correlated and related to benthic macroinvertebrate indices of biological integrity through non-parametric statistical procedures. It was found that the presence of larger sediment size classes was more significant, in a positive relationship, than the negative association of the finer particles. Medium to fine silt, channel stability, channel slope, and the percent below 2-mm from a modified Wolman pebble count, were also found to be significant parameters in their relationship to biological integrity scores. The analyses revealed the importance of the larger bed materials and heterogeneity of bed sediment along the riffles. The significance of these results indicates that habitat heterogeneity from larger bed substrate material may be more relevant to the biological integrity than the weaker effects of fine sediment. The negative impact from fine sediments were observed and found to be mostly in the size range of medium to fine silt. Overall, the processes from the Rapid Geomorphic Assessment, including channel stability, and slope, were found to have good correlations to biological integrity.

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Shannon Bennett

M.S. Environmental Engineering -- University of Tennessee 2006


THESIS: Use of a Dynamic Sediment Delivery Model for Watershed Planning in Beaver Creek, Knox County, Tennessee


The Beaver Creek watershed is rapidly urbanizing. The purpose of this research is to provide a better understanding of sediment transport in watersheds as a function of urbanization and land disturbance, and evaluate Best Management Practices scenarios. The Annualized Agricultural Non-Point Source Pollutant (AnnAGNPS) dynamic sedimnent loading model was used to model different simulation scenarios of urbanization and disturbance in the watershed. Results demonstrate the impacts of urbanization and land disturbance on sediment yield. Urbanization in the Beaver Creek watershed has caused an increase in runoff, sediment yield delivery, and bank erosion. The model predicts the current sediment yield (including bank erosion) is 137.47 T/day. Increased land disturbance significantly increases the sediment yield. AnnAGNPS results show development in the lower watershed generates more sediment than development in the middle and upper watershed. Disturbance on hillslopes has a great impact on sediment yield. Sediment yield decreased with more efficicient BMP scenarios. Development can continue without significantly increasing sediment yield if effective BMPs are utilized in the Beaver Creek watershed.

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Brantley Thames

M.S. Environmental Engineering-- University of Tennessee 2005

THESIS: The Effects of Urbanization on the Streambed Sediment Characteristics in a Ridge and Valley Watersheds

 

Urbanization causes flow and sediment regime changes, which leads to alterations in the bed sediment characteristics and degradation of the ecological habitat. Evidence shows that changes in the characteristics of streambed sediment occur in urbanized watersheds; however a link between urbanization and changes in streambed sediment is not well established in the literature. Limited support in the literature does suggest that urbanization is linked to a decline in the diversity of algae, invertebrate, and fish populations. Relationships between urbanization and bed sediment characteristics were explored by three studies using the AnnAGNPS and CONCEPTS models. AnnAGNPS is a GIS-based sediment delivery model with land erosion rates determined by the revised Universal Soil Loss Equation (RUSLE) and sediment yield rates determined by the Hydrogeomorphic USLE (HUSLE) for watersheds primarily dominated by agricultural land use. CONCEPTS is a sediment transport and channel adjustment model that routes sediment input from AnnAGNPS and sediment inputs from channel bed and bank erosion. Both models were developed by the United States Department of Agriculture – Agricultural Research Service (USDA ARS). The research objectives for this project included: 1) conducting a sensitivity analysis of the AnnAGNPS and CONCEPTS models to evaluate the significance of various model inputs that incorporate the mosaic of urban land use and require field measurements for the non-urbanized and urbanized subwatersheds, 2) producing and executing several combinations of model run simulations with altered runoff and erosion from the hillslope using the entire AnnAGNPS-CONCEPTS modeling couple to simulate varying levels of urbanization, and 3) evaluating AnnAGNPS model results of 15 urban and non-urban subwatersheds across Beaver Creek watershed to gain insight to dominant sediment delivery dynamics resulting from urbanization using a multivariate cluster analysis between the model output, field measurements, stream power, subwatershed area, and percent urbanization. The studies addressing the first and second research objectives were conducted using the geographic data in two subwatersheds of the Beaver Creek watershed in Knox County, Tennessee, whereas the third study used data across the entire Beaver Creek watershed. The two subwatersheds include Hines Branch, which is a highly disturbed urban subwatershed, and Cox Creek, which is a subwatershed with minimal urban development. The results from the three studies included the following main conclusions: 1) the AnnAGNPS and CONCEPTS models were fairly insensitive to the model input parameters tested in the sensitivity analysis on an individual basis; however, when comparing the sensitivities between the urban and non-urbanized subwatersheds for the AnnAGNPS analysis, the percent difference between the sensitivity slopes for each model input parameter ranged from 150 to 300 percent; 2) simulations with altered runoff and erosion from the hillslope showed that altered runoff had a greater impact on the bed sediment characteristics and sediment yield; and 3) the cluster analysis of the five watershed characteristics illustrated that percent urbanization of each subwatershed and suspended sediment from AnnAGNPS model output over subwatershed stream power and total subwatershed area were the most related to the bed sediment size distributions collected at each site. Assuming the AnnAGNPS-CONCEPTS modeling couple represents the physical watershed and channel processes, then this thesis shows that urbanization does impact bed sediment characteristics, and it appears hydrology is more of a controlling factor to bed sediment characteristics than hillslope erosion.served and found to be mostly in the size range of medium to fine silt. Overall, the processes from the Rapid Geomorphic Assessment, including channel stability, and slope, were found to have good correlations to biological integrity.

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Christopher Howley

M.S. Environmental Engineering -- University of Tennessee 2006


THESIS: The Relationships Among Culvert Characteristics and Culvert Sedimentation


TThe purpose of this study was to investigate the relationships among various culvert characteristics and their effect on sediment deposition in culverts. The analysis included obtaining site specific field data, watershed modeling, culvert modeling, and data interpretation. Field data was acquired for 39 culvert locations scattered across the City of Knoxville. The locations were selected based on previous maintenance records and a good distribution of characteristics subject to evaluation. The data collected included slopes, culvert material types, culvert sizes, culvert lengths, headwater depths, upstream channel conditions and downstream channel conditions. Obtaining this information required a detailed site inspection including surveying, culvert and sediment measuring, and a visual inspection and site evalution. In addition, hydrologic and hydraulic models were also used to evaluate culvert site characteristics at study locations. The information from field investigation as well as model output was evaluated by graphical depictions and statistical comparisons. Also, data were evaluated for culvert locations that had a minimal amount of sediment build up versus those culverts with a significant sediment buildup. Findings revealed that six of the characteristics evaluated showed some relationship with culvert sedimentation. Culvert characteristics were divided into three tiers of influence. Each tier was analyzed and assigned a numerical value in order to develop a maintenance index. This index is proposed for use in evaluating whether a culvert, existing or proposed, may be prone to sediment deposition problems. Recommended research includes the relationship between debris and culvert sedimentation, the effect of the sediment yield from a watershed on culvert sedimentation, the relationship between the seasonal rainfall effects and culvert sedimentation, and additional statistical analysis on the data compiled within this study.

 

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Angela Brawley

M.S. Environmental Engineering-- University of Tennessee 2008

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