According to the US Environmental Protection Agency (USEPA) sediment is a leading cause of water quality impairment (US EPA, 2002). The annual costs of sediment pollution in North America alone are estimated to range between $20 and $50 billion (Pimentel et al., 1995; Osterkamp et al, 1998, 2004). Due to the large spatial and temporal variations inherent in sediment transport, suspended sediment measurement is challenging. The overall goal of this research was to develop and test an inexpensive sensor for continuous suspended sediment monitoring in streams. This study was designed to determine if the gain and phase components of permittivity could be used to predict suspended sediment concentrations (SSC). A bench-scale suspension system was designed and tested to guarantee that there were no significant differences in the sediment suspension vertically or horizontally within the system. This study developed prediction models for SSC with input variables of temperature, specific conductivity, and gain and/or phase at multiple frequencies. The permittivity sensor is comprised of an electrode, power source, and a control box or frequency generator. Fixed and mixed effect, multiple, linear regression models were created and compared for target frequencies. However, it was not possible to meet the normality requirements for prediction accuracy. Partial Least Squares (PLS) regression techniques were also applied to gain and phase data for 127 of the 635 frequencies. The three models with the lowest error between predicted and actual values of SSC for validation were further tested with nine levels of independent validation data. The largest model error (error>50%) occurred for the top three models at 0 and 500 mg/L. At the higher concentrations error varied from 1-40%. Once the treatment levels, of the independent validation data set, were near 1000 mg/L the prediction accuracy increased for the top three models. Model 3A, a phase based model, preformed the best. Model 3A was able to predict six of the nine independent validation treatment levels within 300 mg/L. Future research will provide additional laboratory and field testing of the prototype sensor. / Ph. D.

Thesis advisor: Noah P. Snyder / Centuries-long intensive land use change in the northeastern U.S. provides the opportunity to study the response timescale of geomorphic processes to anthropogenic perturbations. In this region, deforestation and the construction of dams following European settlement drastically altered the landscape, leading to the impoundment of sediment in mill ponds. This legacy sediment continues to be released into transport decades after a dam has been removed or breached. Geochemical tracers can help distinguish sediment sources and understand how sediment moves through a watershed. The South River in western MA is located in a formerly glaciated watershed, and these surficial deposits compose 98% of the area. It experienced two generations of damming, beginning with smaller mill dams in the 18th-19th centuries, followed by the construction of the Conway Electric Dam (CED), a 17 m tall hydroelectric dam in the early 20th century. Legacy sediment deposits from sediment stored behind mill dams cover 1.5% of the watershed area. The CED is located near the outlet of the river, providing a century-long depositional record for the watershed, during reforestation. I hypothesize that sediment mobilized from human activity will contain a different geochemical signature than glacial material, that recent erosion in the watershed is primarily from anthropogenic legacy deposits rather than from glacial age landforms, and channel widening is occurring in reaches of the channel composed of legacy sediment, rather than in glacially confined reaches. These hypotheses were tested through a two part investigation, consisting of a sediment tracing study using Hg, and a Geographic Information Systems (GIS) analysis of channel changes using aerial photographs from 1940 and 2014. Samples were collected from river bank exposures of 11 glacial deposits and four mill pond legacy sites. Two vibracores measuring 476 and 500 cm were collected in reservoir sediment stored behind the CED in 2013 and 2017, respectively. Hg concentrations range from 1-4 ppb in glacial sediment, 3-380 ppb in legacy sediment, and 2-18 ppb and 7-50 ppb in the two CED cores. I used Hg as a tracer to estimate percent contributions to the CED reservoir from each watershed source during the 20th century. Results from a sediment mixing model suggest glacial sources contributed 32 ± 15%, and legacy sediment deposits contributed 68 ± 15% during the 20th century. Based on 137Cs dates on the cores, high amounts of legacy sediment filled in behind the CED prior to 1953 (74 ± 35 %), and background erosion from glacial deposits dominated from 1953 until the reservoir was filled in the 1980s (63 ± 14%). GIS analyses using aerial photographs from 1940 and 2014 indicate that the channel did not significantly widen along any section of the river, however, increases in sinuosity (up to 12%) occurred in the legacy sediment dominated reaches of the channel, and minor increases (1-2%) occurred in the glacial reaches. Overall, these analyses show an increase in the amount of sediment released in the channel as a result of mill dams breaching through the mid-19th to early 20th centuries, and suggest a short recovery timescale response from this land-use change. / Thesis (MS) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

Föroreningar av metaller är ett problem längs med kusterna, vilket har en negativ inverkan på vattenlevande organismer och miljön. Orsaken till detta beror till stor del på pågående utsläpp från tätorter, hamnar, industrier och på ”gamla synder (då det inte fanns några detaljerade miljölagar som reglerade spridningen av föroreningar från exempelvis industriprocesser)”. Utsläpp av föroreningar behöver inte bara komma lokalt utan kan också transporteras via avrinningsområdena och via atmosfäriskt nedfall. Idag arbetar länsstyrelsen med att invertera och sanera förorenade områden, men för att kunna ta reda på hur det ligger till med kusterna och hamnarna är sedimentprovtagningar ett måste. Att analysera data från sedimentprover kan vara speciellt utmanande eftersom det finns många olika faktorer som kan ha betydelse när data skall analyseras. Det kan vara faktorer som bottentyper, utspädning, kornstorlekar mm i en miljö som är speciellt utsatt för omrörningar. Syftet med detta arbete är att identifiera åtgärder som kan bidra till att förbättra analysen av föroreningar från sedimentundersökningar då det finns faktorer som kan påverka föroreningssignalen. Till detta arbete har data från Sveriges Geologiska Undersökning (SGU) använts. Provtagningarna genomfördes längs med kusten i Kalmarsund under åren 1998, 2003 och 2008. Dessa data har tidigare studerats med fokus på metallkoncentrationer. I detta arbete ligger fokus istället på att göra fördjupande jämförelser genom att studera morän, organiskt material, samt tillämpningen av normaliseringar och elementförhållanden. Även data från Structor Miljö Göteborg AB som tagit prover i Oskarshamns hamn under 2011 med hjälp av sedimentfällor har använts. Syftet är att göra en jämförelse med SGU:s provtagningar, samt att undersöka miljögiftsbelastningen och sedimentationshastigheten i Oskarshamns hamn och ytterområde. Resultatet visar att spridningen av metaller kan förbättras genom att studera koncentrationerna tillsammans med organiskt material, normalisering mot organiskt material och naturliga utsläpp av metaller ifrån morän. Resultatet visar också att sedimentfällor är ett utmärkt komplement till vanliga sedimentprovtagare.

A key goal of tsunami research is to quantitatively reconstruct flow parameters from paleotsunami deposits in order to better understand the geohazards of coastal areas. These reconstructions rely on grain-size and thickness measurements of tsunami deposits, combined with simple models that allow an inversion from deposit characteristics to wave characteristics. I conducted flume experiments to produce a data set that can be used to evaluate inversion models for tsunami deposition under controlled boundary conditions. Key variables in the flume experiments are sediment grain-size distribution, flow velocity and depth, and depth of water ponded in the flume before the tsunami bore was released. Physical experiments were run in a 32 m-long outdoor flume at The University of Texas at Austin. The flume has a head box with a specialized mechanical lift gate that allows instantaneous release of water to create a bore. Various sediment mixtures (silt to very coarse sand) are introduced to the upstream end of the channel as a low dune positioned just below the lift gate. The bore entrained the sediment mixture, producing an unambiguous suspension-dominated deposit in the downstream half of the channel. Deposits were sampled for grain-size and thickness trends. The experimental results capture characteristics of many recent and paleotsunami deposits, including consistent fining in the transport direction. In addition to overall fining, trends in deposit sorting and coarse (D95) and fine (D10) fractions reveal the importance of sediment-source grain-size distribution on tsunami deposit attributes. / text

MESHWR / Department of Hydrology and Water Resources Management / This research was aimed at determining the impact of rainfall events on suspended sediment concentration (SSC) and water quality and links to sediment management in Dzindi River Catchment, Limpopo Province. Rainfall events of different magnitudes and duration erode different sediment volumes resulting in significant variation in sediment loads of receiving water bodies. This affects the water quality of such water bodies. Water samples for water quality and suspended sediment measurements were collected after each rainfall event for periods of six and five months, respectively, in two consecutive rainy seasons. The periods were from October 2012 to March 2013 and December 2013 to April 2014. The samples were collected from selected cross-sections at four sites along Dzindi River. Physical water quality parameters or water quality indicators (pH, Electrical conductivity (EC) and turbidity) were measured with multi 340i/set multimeter and Orion Aqua Fast II turbidity meter, as they are the indicators of the overall status of the water quality. Suspended sediment concentration (SSC) for each sample was measured using evaporation method. SSC at each cross section was computed using the mean discharge-weighted formula. Field survey was undertaken to identify land use activities that promote erosion and hence sedimentation. The relationship between SSC and rainfall magnitude was determined using sediment rating curves. Water quality and sedimentation status at each cross-section together with the information from the GIS map aided in identifying and recommending the best sediment management strategies for different sites in the study area. pH values for October 2012 to March 2013 and December 2013 to April 2014 were both higher in the downstream site of the river catchment, which is Manamani site. Lowest pH was found in the upstream and mid-stream sites, which were Dzindi water treatment works (DWTW) and Tshisaulu, respectively. Tshisaulu had highest EC value and Lwandani had lowest value, respectively, for the period of October 2012 to March 2013. DWTW had the highest EC value and Tshisaulu had the lowest EC value, respectively, for the period of December 2013 to April 2014. Manamani had high turbidity value and Lwandani had low turbidity value for October 2012 to March 2013. Turbidity for DWTW for the period of December 2013 to April 2014 was the highest and Tshisaulu had the lowest turbidity value. Sediment rating curves for DWTW, Tshisaulu and Manamani, respectively, had coefficient of determination (R2) values of 0.185, 0.53 and 0.99, respectively. Different sediment management strategies, including slope and bank protection and minimum and mulch tillage, were recommended based on topography and land use activities and these strategies can prevent soil erosion and minimize transport of sediments into the river.

No / The suspended sediment transport capacity is important for estimating the suspended load concentration and the ecological environment of the river. So far, few studies have been conducted to investigate the suspended sediment transport capacity in the vegetated sediment-laden flow. In this study, a new formula is derived to predict the sediment transport capacity in a vegetated flow by considering the absolute value of the energy loss between the sediment-laden flow and the clear water flow. Finally, the formula is expressed in a practical form by using the logarithmic matching method.

No description available.

Knowledge of fine sediment delivery (both timing and loading) is fundamental to the assessment of non-point source pollution in estuarine environments. This study comprised three key components that led to the development of a fine sediment and particulate associated phosphorus budget in a typical agricultural estuary. Firstly, to explore catchment inputs, turbidity and flow were monitored continuously upstream of the freshwater/saline interface on the main stem channel of the south Devon River Avon, which drains a medium sized agricultural catchment (area 340 km2), in southwest UK. Thirty-five storms were studied in detail; and the hydrological and suspended sediment load response was observed to be highly variable. Suspended sediment concentrations (SSC) reached a maximum of 804 mg L-1 and sediment load varied from 3 to 227 t per hydrological event. Most sediment load was concentrated in winter months when competent flows occur frequently. Hydrological response was also variable in terms of lag, hydrograph shape and maximum discharge wherein the response to hydrological drivers was not consistent. Analysis of key storm parameters indicated that the hydrological response of the catchment was affected by the total amount of precipitation and antecedent rainfall history but the spatial pattern in rainfall across the catchment in relation to the spatial pattern of sediment sources was the key factor influencing total load. In the second component, examination of the sediment-associated phosphorus concentrations in the surface sediment in the Avon estuary was undertaken to evaluate spatial variation in concentration as influenced by the sediment storage dynamics of key geomorphological zones i.e. saltmarshes, intertidal flats and sandy shoals. Phosphorus concentrations ranged from 1524 to 68 mg kg-1 with higher concentrations found in saltmarsh. While there was no observed relationship between key sediment properties, particle size and total organic carbon within the different geomorphic units, a clear trend in particle size and particulate phosphorus concentration was observed longitudinally between mudflat zones linked to the sedimentation dynamics of the estuary. Furthermore, the relationship of particulate phosphorus concentration to organic matter content was modified by saltmarsh vegetation inputs to the sediment column. The final component of the work drew on evidence from a GIS and field-based survey to estimate (i) the total fine sediment and associated particulate phosphorus loading of the estuary and (ii), in conjunction with river flux data and literature evidence, the total fine sediment and PP storage and the annual sediment budget (inputs, storages and output) for the study estuary. The total amount of fine sediment stored in the estuary was ca. 99000 t which equated to 40 - 100 years of the annual sediment load of the river. Approximately 50% of all fine sediment that currently enters the estuary was estimated to be retained in storage supporting the important role of estuarine sediment sink zones in the attenuation of phosphorus. The total particulate phosphorus storage in estuary fine sediment was estimated to be 20 – 40 times the measured annual catchment particulate phosphorus input. Future changes in catchment sediment supply dynamics linked to catchment restoration programmes and soil conservation initiatives could destabilise estuarine sediment sinks and this has potentially important implications for future estuarine water quality. There is a need for further work on the potential bioavailability of estuarine sediment stored phosphorus.

The effect of non-cohesive sediment on wave-induced bottom boundary layers was examined experimentally. Fluid velocity and sediment concentration were measured simultaneously in a sheet regime generated in a u-shaped oscillating water tunnel. A major obstacle to the understanding of fluid-grain flow has been the absence of suitable measuring devices. Thus, previous experimental investigations have been concerned primarily with low sediment concentration flows. For this study, a probe was developed to measure the instantaneous variations in sediment concentration based on the electrical conductivity of the fluid-grain mixture. Unlike earlier concentration devices, this probe is non-intrusive and is capable of measuring a wide range of sediment concentrations; from close packing within the bed to low concentration suspended load. Horizontal fluid velocities were measured simultaneously using Laser Doppler Anemometry in backscatter mode. Height and time-dependent velocity and concentration profiles were obtained for differing wave and sediment conditions. Values of the shear stress calculated from the momentum integral were found to be an order of magnitude larger than in sediment-free flows. The variation in shear stress with distance from the bed is clearly dependent on the thickness of the movable bed and also on the sediment flow regime. As expected, the eddy viscosity varied significantly during the wave cycle. The time-mean eddy viscosity decreases with height above the movable bed and at large distances from the bed, fluctuates about the mean. The sediment concentration measurements provide a comprehensive data set for sediment transport in sheet flow and near sheet flow regimes. The sediment concentration was found to be time-dependent with the amplitude and form of the temporal variation dependent on distance from the bed, wave amplitude and velocity, and sediment characteristics. With increasing wave amplitude and velocity, the number of peaks in the concentration profile increased while the magnitude of the peaks decreased. Fluid velocity and sediment concentration measurements were used to calculate rates of sediment transport which were compared with predictions from existing models.

No description available.