Patterns of surface sediment concentration distribution in rivers are significant for understanding the broad ranges of fluvial environmental systems. In the case of the Amazon Basin, the complexity in the sediment pattern distribution is affected by the anabranching channel pattern of the Amazon River, the input by tributaries (some of which are among the largest rivers on earth) and the existence of huge and complex floodplains. Until recently, the assessment of sediment fluxes has been concentrated on hydro-sedimentological techniques in the Amazon Basin; however, efforts on characterizing the patterns of sediment transport have been neglected. This study aims to improve the understanding of the pattern of sediment distributions over a large scale in the Amazon River by estimating surface sediment concentration with remote sensing techniques. Field acquired surface sediment concentration values were supplied from three gauging stations representing the upstream, midstream and downstream sections of the Amazon River from 2000 to 2010 and calibrated with MODIS surface reflectance products (N=207, 232, 313, respectively). Empirical models were derived with robust causalities (0.63<R2<0.92) between field surface sediment concentration and surface reflectance from each station; however, sensitivity of reflectance around each stations were shown to be significantly affected by the local hydrological behaviors, leaving implications on analysis of the geomorphic characteristics affecting these associations. Overall, the capability of the remote sensing-based platform introduced in this study is successfully demonstrated by capturing the spatial and temporal variability of surface sediments in the Amazon River Basin, which is the largest and the most complex river system on earth. / text

<p> This study describes the analysis of orientation of elongate quartz grains in massive turbidite sandstones from the Chetco Formation (Jurassic) of southwestern Oregon. Inferences on depositional fabric of this resedimented facies are made.</p> <p> Grain orientation in the plane parallel to bedding is generally not highly significant statistically, and current direction, supplied by imbrication, is not persistent vertically through the beds. However, a rotation pattern of current direction in each bed is detected.</p> <p> Variations in orientation distribution could represent variations in sediment concentration of the flow and in the rate of deposition.</p> / Thesis / Bachelor of Science (BSc)

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.

Continental shelves connect land and the ocean and also play a major role through time in the storage and re-distribution of terrigenous sediments to the ocean. Most of the sediments which origin in land and very shallow waters are deposited on the continental shelf. Sediment entrainment and movement in the coastal ocean are dominated by the combined effect of waves and currents within the benthic boundary layer. Our study intends to examine the relation between currents, waves and acoustic echo intensity in a wave-current boundary layer. The site of the study was located southeast off Kaohsiung Harbor entrance in southern Taiwan on the inner shelf. Between April 16 and May 1, 2004, a tetrapod was deployed with an upward-looking ADCP (Aquadopp Profiler), a CTD with an OBS (XR-420). Another downward-looking ADCP was mounted at 2 m above bed (mab). The interval of the data collection was one hour. Water samples were pumped in seven time-segments (4 in the neap tide, 3 in the spring tide) through the experimental period at 1 and 0.5 mab, respectively for suspended sediment concentration (SSC) analysis in the laboratory. Aquadopp Profiler not only records 3-D current data but also measures the echo intensity (EI). The echo intensity is proportional to the amount of backscattering particles in the water column. The acoustic intensity could be a useful reference for the total concentration of the suspended particles. Our preliminary findings indicate strong tidal control on the dynamics of suspended particles in the benthic boundary layer. The wave field is also modified by the tidal. The form number of the observed tides is 1.87, which indicates mixed tides with a predominantly diurnal component. The data were analyzed using empirical orthogonal (eigen) function (EOF) analysis. The results indicate that the tidal current dominated the alongshore current. Its period is 24.67 hours. The echo intensity are dominated by the current shear velocity. The observations show that the maximum thickness of wave boundary layer and wave-current boundary layer at the experiment site is about 0.9 cm and 1.24 cm respectively. Cross-correlation analysis results among the roughness length, the thickness of wave boundary layer, and the thickness of wave-current boundary layer show that the roughness length correlates negatively to the thickness of both boundary layer. The data were analyzed by spectrum analysis. The results indicate that wave boundary layer were dominated by the low frequency current. The wave-current boundary layer and the roughness length were dominated by the semidiurnal tides.

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.

Estuaries are valuable ecosystems that are easily affected by human activities within the watershed. One determinant of water quality for in an estuary is the presence of suspended sediments. The use of satellite sensors to remotely sense visible and near-infrared reflectance allows for suspended particulate matter (SPM) and suspended particulate inorganic matter (SPIM) concentrations to be monitored on a repetitive synoptic scale. Previously presented algorithms for relating remote sensing reflectance (Rrs) and SPM/SPIM concentrations were evaluated for the Weeks Bay estuary in Alabama. Additionally, numerous potential SPM/SPIM concentration retrieval algorithms using the Landsat-8 satellite were determined through regression analysis, as well as through the consideration of the inherent optical properties of the water body. The most robust empirical algorithm produced an RMSE of 12.50% and utilized the band combination of Ln(Band4)/Ln(Band3), while the most robust semi-analytical algorithm produced an RMSE of 16.34% and utilized the band combination of Band4/Band3.

Yes / Simulation of the suspended sediment concentration (SSC) has great significance in predicting the sediment transport rate, vegetation growth and the river ecosystem in the vegetated open channel flows. The present study focuses on investigating the vertical SSC profile in the vegetated open channel flows. To this end, a model of the dispersive flux is proposed in which the dispersive coefficient is expressed as partitioned linear profile above or below the half height of vegetation. The double-averaging method, i.e. time-spatial average, is applied to improve the prediction accuracy of the vertical SSC profile in the vegetated open channel flows. The analytical solution of SSC in both the submerged and the emergent vegetated open channel flows is obtained by solving the vertical double-averaging sediment advection-diffusion equation. The morphological coefficient, a key factor of the dispersive coefficient, is obtained by fitting the existing experimental data. The analytically predicted SSC agrees well with the experimental measurements, indicating that the proposed model can be used to accurately predict the SSC in the vegetated open channel flows. Results show that the dispersive term can be ignored in the region without vegetation, while the dispersive term has significant effect on the vertical SSC profile within the region of vegetation. The present study demonstrates that the dispersive coefficient is closely related to the vegetation density, the vegetation structure and the stem Reynolds number, but has little relation to the flow depth. With a few exceptions, the absolute value of the dispersive coefficient decreases with the increase of the vegetation density and increases with the increase of the stem Reynolds number in the submerged vegetated open channel flows. / the Natural Science Foundation of China (Nos. 11872285 and 11672213), The UK Royal Society – International Exchanges Program (IES\R2\181122) and the Open Funding of State Key Laboratory of Water Resources and Hydropower Engineering Science (WRHES), Wuhan University (Project No: 2018HLG01)

Yes / Simulation of the suspended sediment concentration (SSC) has great significance in predicting the sediment transport rate, vegetation growth and the river ecosystem in the vegetated open channel flows. The present study focuses on investigating the vertical SSC profile in the vegetated open channel flows. To this end, a model of the dispersive flux is proposed in which the dispersive coefficient is expressed as partitioned linear profile above or below the half height of vegetation. The double-averaging method, i.e. time-spatial average, is applied to improve the prediction accuracy of the vertical SSC profile in the vegetated open channel flows. The analytical solution of SSC in both the submerged and the emergent vegetated open channel flows is obtained by solving the vertical double-averaging sediment advection-diffusion equation. The morphological coefficient, a key factor of the dispersive coefficient, is obtained by fitting the existing experimental data. The analytically predicted SSC agrees well with the experimental measurements, indicating that the proposed model can be used to accurately predict the SSC in the vegetated open channel flows. Results show that the dispersive term can be ignored in the region without vegetation, while the dispersive term has significant effect on the vertical SSC profile within the region of vegetation. The present study demonstrates that the dispersive coefficient is closely related to the vegetation density, the vegetation structure and the stem Reynolds number, but has little relation to the flow depth. With a few exceptions, the absolute value of the dispersive coefficient decreases with the increase of the vegetation density and increases with the increase of the stem Reynolds number in the submerged vegetated open channel flows. / Natural Science Foundation of China (Nos. 11872285 and 11672213), The UK Royal Society – International Exchanges Program (IES\R2\181122) and the Open Funding of State Key Laboratory of Water Resources and Hydropower Engineering Science (WRHES), Wuhan University (Project No: 2018HLG01).

Yes / Based on the Lagrangian approach, this study proposes a random displacement model (RDM) to predict the concentration of suspended sediment in vegetated steady open channel flow. Validation of the method was conducted by comparing the simulated results by using the RDM with available experimental measurements for uniform open-channel flows. The method is further validated with the classical Rouse formula. To simulate the important vertical dispersion caused by vegetation in the sediment-laden open channel flow, a new integrated sediment diffusion coefficient is introduced in this study, which is equal to a coefficient multiplying the turbulent diffusion coefficient. As such, the RDM approach for sandy flow with vegetation was established for predicting the suspended sediment concentration in low-sediment-concentration flow with both the emergent and submerged vegetation. The study shows that the value of for submerged vegetation flow is larger than that for emergent vegetation flow. The simulated result using the RDM is in good agreement with the available experimental data, indicating that the proposed sediment diffusion coefficient model can be accurately used to investigate the sediment concentration in vegetated steady open channel flow. / National Natural Science Foundation (No. 51439007, 11672213, and 11872285); Open Funding of State Key Laboratory of Water Resources and Hydropower Engineering Science (WRHES), Wuhan University (Project No: 2018HLG01)

Yes / Ice cover formed on an alluvial channel can significantly alter the flow characteristics, such as the vertical distributions of streamwise velocity and shear stress, and hence the water and sediment transport process. The vertical profile of the suspended sediment concentration in the ice-covered alluvial channels with steady uniform flows is investigated in this study. To calculate the suspended sediment concentration, we are based on the Schmidt O’Brien equation and deduce an analytical model that employs an existing eddy viscosity model and a modified formula of the sediment fall velocity considering the common effects of the upper and lower boundaries. The proposed analytical model is then validated by using available experimental data reported in the literature. The predicted accuracy of the proposed model is evaluated through error statistics by comparing to previous modeled results. The relative concentration profiles of the suspended sediment are subsequently simulated by applying the validated analytical model with different characteristic parameters. Results show that the relative concentration decreases with the increase of both the ice cover roughness and the sediment fall velocity. The uniformity of the relative concentration distribution is closely related to the value of the proportionality parameter σ, revealing the physical mechanism that the more prominent the turbulent diffusion effect is, the more uniform the relative concentration profile is. / This work was supported by the National Natural Science Foundation of China (grant 604 numbers 52020105006 and 11872285) and the Open Funding of State Key Laboratory of Water Resources and Hydropower Engineering Science (WRHES), Wuhan University (Project number 2018HLG01).