- Characteristics of Fine Sediment Embeddedness: Towards Understanding Drainage Network Transport Lags
- Examining Sediment Rating Curve Hysteresis with State-of-the-Art Sensors
- Sediment Source Tracking in Urban Watersheds: An Application in the Second Creek Observatory
- Evaluation of Fecal Indicators at Recreational Beaches in Central Tennessee
- Combined Field Study of Turbulence and Bed Morphology in Mountainous Boulder Arrayed Stream
Project Number: 2017TN131B
Title: Characteristics of Fine Sediment Embeddedness: Towards Understanding Drainage Network Transport Lags
PI: John Schwartz, Dept. of Civil & Environmental Engineering, University of Tennessee
The State of Tennessee contains many waterbodies that have been identified on the 303(d) list as impaired or threatened, by which they do not meet designated beneficial uses including biological integrity [40 CFR Part 130; TCA 69-3-101 and TDEC Rules Chapter 1200-4]. A majority of streams listed are impacted by excessive sedimentation in channels causing physical habitat degradation, thus reducing biological integrity. The Tennessee Department of Environment and Conservation (TDEC) is required by statutes to produce total daily maximum loads (TMDLs) for 303(d) listed streams impacted by siltation and habitat alteration. Watershed impacts from excessive sedimentation are an international issue, including the Czech Republic. Colleagues at the Czech Technical University (CTU), Civil Engineering Faculty are interested in collaborating on sediment transport and channel erosion problems. We have agreed to investigate sediment dynamics in the channel associated with embeddedness, where fine sediment (silt or smaller) becomes embedded into alluvial channel materials consisting of mixed bedload. The focus of this research will be assessing the role of biofilms associated with the retention of fine sediment into the channel bed alluvium. A McNeil sediment sampler will be used to sample bed material without the loss of the fine sediment fraction, in which the samples will be analyzed for particle size fractions and organic content. Sediment collections will be co-located conducted at sites with Tennessee benthic macroinvertebrate index (TMI) bioassessment data. In addition, field experiments will be conducted examining the influx of fine sediment into a standard gravel matrix, in a specially constructed sampling device placed on the stream bed. This research project will be conducted by an undergraduate student over the summer period (May-August 2017). Similar research will be conducted on a research stream by the CTU. For the long-term, Dr. Schwartz will use this CTU collaboration to publish a peer-reviewed journal article, and start building the case for a future National Science Foundation (NSF) Partnership for International Research and Education (PIRE) grant. As hypotheses, the expected outcomes include a statistically significant response that biofilms play a key role in embeddedness, embeddedness quantified by a McNeil sampler will be correlated to TMI scores and directly correlated with biological impairment, and development of a relationship of fine sediment influx into a gravel matrix, used towards predicting embeddedness in streams.
Project Number: 22017TN132B
Title: Examining Sediment Rating Curve Hysteresis with State-of-the-Art Sensors
Team: Achilleas Tsakiris, Thanos Papanicolaou, and Jon Hathaway, Dept. of Civil & Environmental Engineering, University of Tennessee
Sediment rating curves, which are relations between sediment transport rates and water flow often exhibit large degrees of variability, which limits their predictive ability. This variability is typically the outcome of the hysteresis, or time lag, between the water discharge hydrographs and the sediment transport fluxes. The type and magnitude of hysteresis is controlled by the amount as well as the timing of the supplied sediment from upstream and lateral sources relative to the water flow changes during the rising and falling limbs of a storm hydrograph. The variability in rating curves due to hysteresis is accentuated by changes in water temperature, which the fall velocity of sediment, and thus their transport mode, i.e., suspension or bedload. However, the effects of water temperature on sediment rating curves still remain poorly documented. Variability in sediment supply relative to the water flow in the state of Tennessee is often attributed to changes in land management practices in agricultural landscapes that profoundly affect the amount and timing of sediment delivery in rivers, as well as to the encroaching urbanization that leads to a decrease of sediment inputs and increase of runoff into urban rivers. More importantly, the dams and reservoirs in many Tennessee rivers limit sediment supply to the downstream reaches, while simultaneously increasing the flashiness of sediment supply during water releases. These factors are further promoted by the global climatic change that is expected to increase the chances of excessive rainfall amounts. An improvement of the predictive ability and reduction of the uncertainties of sediment rating curves due to the hysteresis phenomenon is necessary for the design and management of reservoirs, as uncertainties in sediment rating curves translate to inaccurate boundary conditions of predictive sediment transport models and errors in estimates of reservoir size and dam lifetime using these predictions. Along the same lines, accurate sediment rating curves are needed for training the morphodynamic numerical models used for designing and placing hydraulic structures, such as bridge piers and bank protection countermeasures. Further, reduction of the uncertainties in sediment rating curves is needed for water quality assessment, and quantification of the contaminant loads attached to sediment particles, as well as for designing stream restoration practices. This research will involve the installation of a monitoring station that tracks the movement of sediment and the water temperature in an urban stream. The information that will be gathered on the sediment particle travel timing and water temperature monitoring will be combined with simultaneous measurements of key hydraulic parameters for characterizing the hysteresis in the sediment rating curves for different storm hydrographs and supply conditions and with varying water temperature. These additional parameters will be retrieved from the Second Creek Observatory operated by the University of Tennessee in the city of Knoxville, TN. The knowledge that will be gained from this monitoring will be used to characterize the hysteresis phenomenon for various hydrologic and sediment supply conditions and be applied for improving the reliability of sediment rating curves.
Project Number: 2017TN130B
Title: Sediment Source Tracking in Urban Watersheds: An Application in the Second Creek Observatory
Team: Jon Hathaway, Thanos Papanicolaou, and Chris Wilson, Dept. of Civil & Environmental Engineering, University of Tennessee
As urbanization spreads throughout Tennessee, the effect of land use change becomes evident in the form of increased stormwater runoff, pollutant export, and stream degradation. Numerous studies have been performed to better understand these effects and develop methods for their amelioration, but gaps in knowledge still exist. Although the field of urban hydrology is relatively mature, the same cannot be said of urban water quality modeling. Recent studies have shown that current models of sediment export from urban watersheds do not perform well, necessitating new approaches to improve these models. These efforts are hampered by the high spatial variability of land uses in these watersheds, as well as the presence of stormwater conveyance infrastructure which greatly influences system connectivity and conveyance. All these variables lead to difficulty determining sediment source areas for individual storm events. However, sediment source tracking holds promise to aid in understanding these processes. This method has become a recognized tool for determining sediment source areas, but has been performed rarely in urban applications. This study will rely on the Second Creek Observatory to help facilitate an effort to better understand the source of sediments in urban stormwater. Source material from around the watershed will be collected, including samples from construction sites, residential property, and roadways. These samples will be analyzed to determine their isotopic fingerprint. At the same time, three storm events will be monitored at the outlet of the watershed. These events will be well characterized by collecting around 20 samples per event. These samples will also be analyzed to determine their isotopic fingerprint. A mixing algorithm will be applied to these data to determine the sources of sediment for each sample collected during each storm. This will allow an understanding of where the sediments from each portion of the storms originate. These events will also be modeled with methods being developed at the University of Tennessee to better understand and predict small scale hydrologic processes. Through these methods, for each event, the source of runoff will be estimated. The estimated sediment source areas via the isotope analysis will be compared to the hydrologic methods to determine their agreement. If good agreement is discovered, these methods may provide insight into how sediment may be better modeled in urban watersheds by more accurately estimating runoff (and thus sediment) source areas. The objective of this research is twofold; (1) to better understand the sources of sediment in an urban watershed in Tennessee to inform management strategies and develop a methodology for similar studies elsewhere, and (2) to use this initial study as a way to develop new hypotheses for improving water quality modeling in urban watersheds.
Project Number: 2017TN129B
Title: Evaluation of Fecal Indicators at Recreational Beaches in Central Tennessee
PI: Frank Bailey, Dept. of Biology, Middle Tennessee State University
Approximately 59 million people visited a beach in 2010. The visitation and subsequent economic value associated with a beach is intimately linked to the beachs water quality. In the U.S., water quality at coastal and Great Lakes beaches is monitored for the presence of fecal pathogens and associated health risk by enumerating easily culturable surrogate (non-pathogen) fecal indicators in water samples (e.g. Escherichia coli or enterococci). Of 3,762 coastal beaches where water was monitored for fecal pathogens in 2012, 1,504 (40%) had at least one advisory or closure. In addition to water, sand contact has been implicated as a potential health risk to beachgoers due to presence of fecal bacteria, viruses, and associated pathogens, but no federal regulatory criteria have been developed for fecal pathogens in sand. Most research has focused on the presence of fecal indicators and pathogens in beach sand from coastal and Great Lakes locations, while studies at other inland recreational beaches are less represented in the literature. Previous research in our laboratory in summer 2015 at Cedar Creek Recreational Beach at Old Hickory Lake in central Tennessee showed the highest concentration of E. coli in sand samples closest to shore and in the top 10cm of sand, with relatively high concentrations of E. coli in both wet and dry swash zone sand. The proposed project will address the following research questions, with the goal of improving the understanding of fecal indicators found at inland recreational beaches: 1) How abundant are traditional (i.e. E. coli) and alternative fecal indicators (i.e. Bacteroidales and coliphages) and pathogens (i.e. Staphylococcus aureus) in sand and water at Cedar Creek Recreational Area on Old Hickory Reservoir and Barton Springs Recreational Area on Normandy Reservoir in Tennessee? and 2) Do human feces contribute to the fecal indicators and pathogens found at these sites? Beach sampling will occur six times at each site during the peak recreational season from late May through early September 2017 including Memorial Day, Independence Day, and Labor Day. At 5 locations from each site, cores of swash zone sand will be collected by sterile PVC pipe to a depth of ~10cm from both the foreshore (dryer sand, ~0.5m inland from the shoreline) and the intertidal (water-inundated) zone (~0.5m into the water from the shoreline). Water samples will also be collected in sterile plastic bottles at 3 locations per site in ~0.5m deep water. Using culture-based methods, E. coli, Staphylococcus aureus, and methicillin-resistant S. aureus (MRSA) will be measured in water and in sand, with PCR verification of Staphylococcus aureus and MRSA. Presence of human-associated fecal pollution will be assessed by qPCR (quantitative polymerase chain reaction, a molecular genetic technique) targeting HF183 Bacteroides 16s rRNA genetic marker. Coliphages, viruses that infect fecal coliforms, will be measured by EPA Method 1602: single agar layer(SAL)procedure, as an indicator of potential enteric virus presence. This research project will benefit state and federal regulatory agencies by providing data on the presence of fecal bacteria, pathogens and viruses at inland freshwater recreational beaches. These data will have potential implications for both environmental and human health protection and will provide preliminary information to regulators in the likely event sand criteria are developed in the future. From a research standpoint, this will fill a knowledge gap in the literature regarding fecal contamination in sand and water from inland freshwater recreational beaches.
Project Number: : 2017TN133B
Title: Combined Field Study of Turbulence and Bed Morphology in Mountainous Boulder Arrayed Stream
Team: Micha Wyssmann, PhD Student, Advisor, Dr. Thanos Papanicolaou, Dept. of Civil & Environmental Engineering, University of Tennessee
The presence of roughness elements such as boulders and large particle groupings in natural coarse-grained streams, such as those in the mountainous Eastern Tennessee, plays a key role in flow routing and affects stage-discharge relationships. Understanding the stability, sediment entrapment and bedload transport characteristics within these stream reaches is critical to predicting river morphological responses, and their feedback interactions with the flow. In addition, arrays of boulders are a viable stream restoration method in order to dissipate flow energy and provide fish habitat benefits (e.g., Saldi-Caromile et al. 2004). An example restoration usage of a boulder array was carried out in the Elwha River and similar uses for energy dissipation following the removal of low head dams may be useful for stream stabilization and erosion control. With the abundance of coarse-grained mountain rivers and ubiquitous boulders in the Smoky Mountains, an enhanced understanding on the controls that these boulders exert on bedload transport is greatly needed for informing sediment transport management practices, including the design of stream restoration structures and the prediction of the life expectancy of the dams operated by the TVA. Furthermore, the proposed improvements in prediction of both magnitude and timing of bedload transport events would have specific implications for improving sediment models, particularly in the Smoky Mountain watersheds. The overarching objective of my dissertation research is the development of a mechanistic bedload transport model that can predict fluxes in mountain river reaches with ubiquitous boulders, while capturing important timescales of pulsation in bedload transport rates. In these types of streams, macro-roughness elements such as boulders play a significant role in providing additional flow resistance and energy dissipation due to the form drag that they generate (e.g., Baki et al. 2016; Papanicolaou et al. 2012). Through these effects, boulders modify bedload transport characteristics in their vicinity (Yager et al. 2007), and thereby influence stream morphology (Montgomery and Buffington 1997). Specifically, boulders tend to detain incoming mobile bedload by promoting the formation of organized particle groupings (Brayshaw 1984), which subsequently break up at high flows and supply pulses of sediment downstream (Strom et al. 2004). Current bedload transport models do not incorporate in their formulations the aforementioned boulder effects and consequently cannot fully capture either the magnitude or timing of bedload transport events within these types of channels (e.g. Yager et al. 2007; Cudden and Hoey 2003). This has important implications for the accuracy of results from sediment modeling assessments at both the stream and watershed scales, which are in turn employed for sediment management in these rivers. Based on previous research, there are two key mechanisms by which boulders affect bedload transport and deposition, namely, (1) modification of the hydrodynamic flow field within the boulder array, and (2) stimulation of particle-to-particle interactions. These key process influences are hypothesized to govern the development and destruction of particle groupings in the area surrounding boulders, whereby boulders can act as either a sink or a source of sediment and, in turn, modify the magnitude and timing of bedload transport (e.g. Strom et al. 2004; Papanicolaou and Kramer 2005; Papanicolaou et al. 2012; Heays et al. 2014). A primary objective of my dissertation research is to connect bedload movement observations with these two mechanisms in order to describe the effects of boulders on bedload transport.