Master of Science / Department of Biological & Agricultural Engineering / Trisha L. Moore / Excess sediment is a leading cause of stream impairment in the United States, resulting in poor water quality, sedimentation of downstream waterbodies, and damage to aquatic ecosystems. Numerous case studies have found that accelerated bank erosion can be the main contributor of sediment in impaired streams. An empirically-derived "Bank Assessment for Non-Point Source Consequences of Sediment" (BANCS) model can be developed for a specific hydrophysiographic region to rapidly estimate sediment yield from streambank erosion, based on both physical and observational measurements of a streambank. This study aims to address model criticisms by (1) evaluating the model’s repeatability and sensitivity and (2) examining the developmental process of a BANCS model by attempting to create an annual streambank erosion rate prediction curve for the Central Great Plains ecoregion. To conduct the repeatability and sensitivity analysis of the BANCS model, ten stream professionals with experience utilizing the model individually evaluated the same six streambanks twice in the summer of 2015. To determine the model’s repeatability, individual streambank evaluations, as well as groups of evaluations based on level of Rosgen course training, were compared utilizing Kendall’s coefficient of concordance and a linear model with a randomized complete block design. Additionally, a one-at-a-time design approach was implemented to test sensitivity of model inputs. Statistical analysis of individual streambank evaluations suggests that the implementation of the BANCS model may not be repeatable. This may be due to highly sensitive model inputs, such as streambank height and near-bank stress method selection, and/or highly uncertain model inputs, such as bank material. Furthermore, it was found that higher level of training may improve model implementation precision. In addition to the repeatability and sensitivity analysis, the BANCS model developmental process was examined through the creation of a provisional streambank erosion rate prediction curve for the Central Great Plains ecoregion. Streambank erosion data was collected sporadically from 2006 to 2016 from eighteen study banks within the sediment-impaired Little Arkansas River watershed of south-central Kansas. Model fit was observed to follow the same trends, but with greater dispersion, when compared to other created models throughout the United States and eastern India. This increase in variability could be due to (1) obtaining streambank erosion data sporadically over a 10-year period with variable streamflows, (2) BEHI/NBS ratings obtained only once in recent years, masking the spatiotemporal variability of streambank erosion, (3) lack of observations, and (4) use of both bank profiles and bank pin measurements to calculate average retreat rates. Based on the results of this study, a detailed model creation procedure was suggested that addresses several model limitations and criticisms. Recommendations provided in the methodology include (1) more accurate measurement of sensitive/uncertain BEHI/NBS parameters, (2) multiple assessments by trained professionals to obtain accurate and precise BEHI/NBS ratings, (3) the use of repeated bank profiles to calculate bank erosion rates, and (4) the development of flow-dependent curves based on annually assessed study banks. Subsequent studies should incorporate these findings to improve upon the suggested methodology and increase the predictive power of future BANCS models.

No description available.

Doctor of Philosophy / Environmental Design and Planning Program / Timothy D. Keane / The original purpose of this investigation was to develop streambank erosion prediction curves for Northeast Kansas streams. Rosgen's (2001, 2006) methods were employed and eighteen study banks were measured and monitored over a four-year period, summer 2007 through summer 2010. At each study bank, a toe pin and two to three bank pins were set at a recorded longitudinal profile station of the stream. Vertical and horizontal measures from the toe pin to the bank face were taken each summer, 2007 as the baseline measure and 2008 - 2010 as bank change years. Bank profiles were overlaid to gain insight into bank area lost or gained due to erosional or depositional processes. A Bank Erosion Hazard Index (BEHI) and Near Bank Stress (NBS) combination rating was assessed and calculated for each study bank during the initial survey of 2007. The streambanks experienced varied erosion rates for similar BEHI/NBS combinations producing R2 values from 0.43 as the High/Very High BEHI rating and 0.80 as the Moderate BEHI rating. In addition, Moderate BEHI ratings provided higher erosion rates than the High/Very High BEHI rating and curves intersected at lower NBS ratings, suggesting a discrepancy in the fit of the model used in the Northeast Kansas region and conditions. In this light, modification of the BEHI model was evaluated and variables were assessed in the model for additional influence exerted in the Northeast Kansas region. Vegetation seemed to provide the most influence to bank resistance and was more closely evaluated. Banks with and without woody riparian vegetation were then plotted against BEHI and NBS values, as banks lacking woody vegetation eroded at higher rates. This study's findings can allow us to calibrate the BEHI model according to woody vegetation occurrence levels along streambanks in the Black Vermillion watershed. Modifications regarding vegetation occurrence of the BEHI model was completed and the results of these modifications generated R2 values of 0.78 for High/Very High BEHI and 0.82 for Moderate BEHI ratings. High/Very High ratings provided higher predicted erosion rates than Moderate ratings, while the curve slopes did not intersect at lower NBS ratings.

The purpose of this study is to analyze how estimates of an important geomorphic parameter, effective discharge, are impacted by the choice of bed material load equations and flow duration curves (FDCs). The Yang (1979), Brownlie (1981), and Pagosa equations developed by Rosgen (2006) were compared for predicting bed material load. To calculate the bed material load using the Pagosa equations, the bedload and suspended load are calculated separately and the results are added together. To compare the effectiveness of the equations, measured bed material load data from the USGS Open-File Report 89-67 were used. Following the calculations, the equation results were compared to the measured data. It was determined that the Pagosa equations performed the best overall, followed by Brownlie and then Yang. The superior performance of the Pagosa equations is likely due to the equations being calibrated. USGS regression equations for FDCs were compared to a method developed by Dr. David Rosgen in which a dimensionless FDC (DFDC) is developed. Weminuche Creek in southwestern Colorado was used as the study site. Rosgen's DFDC method requires the selection of a streamgage for a stream that exhibits the same hydro-physiographic characteristics as the site of interest. An FDC is developed for the gaged site and made dimensionless by dividing the discharges by the bankfull discharge of the gaged site. The DFDC is then made dimensional by multiplying by the bankfull discharge of the site of interest and the resulting dimensional FDC is taken as the FDC of the ungaged site. The USGS regression equations underpredicted the discharges while Rosgen's DFDC method overpredicted them. Rosgen's DFDC method produced more accurate results than the USGS regression equations for Weminuche Creek. To calculate the effective discharge, the FDC was used to develop a flow frequency curve which was then multiplied by the sediment rating curve. Effective discharge calculations were performed for Weminuche Creek using several combinations of bed material load prediction equations and FDCs. The USGS regression equations, Rosgen's DFDC method, and streamgage data were all used in conjunction with the Yang and Pagosa equations. The Brownlie equation predicted zero bed material load for Weminuche Creek, and was thus not used to calculate the effective discharge. When the USGS regression equations were used with the Yang and Pagosa equations, the calculated effective discharge was approximately 4.5 cms for both bed material load prediction equations. When Rosgen's DFDC method and streamgage data were used with the Yang and Pagosa equations, the effective discharge was approximately 13.5 cms. From these results, it was determined that the bed material load prediction equations had little impact on the effective discharge for Weminuche Creek while the FDCs did influence the results.

This report was sponsored by the Utah Department of Transportation (UDOT) to determine if stream restoration structures could be used as scour countermeasures near state highways and bridges. Scour countermeasures that are effective in preventing erosion exist but that are not so friendly for aquatic organisms. UDOT is interested in finding a countermeasure that is both effective in preventing erosion while not harming aquatic organisms. Stream restoration structures are friendly for aquatic organisms but are prone to failure when flows exceed the design levels. David Rosgen has developed restoration structures that are friendly for aquatic organisms and that have provided streambank protection. These structures are the J-Hook vane, Cross-Vane and W-Weir. Based research done in this report, Cross-Vanes and W-Weirs are best suited to protect bridges because they will protect both sides of a stream bank. For these restoration structures to be reliable at higher flows and shear stresses experienced at bridges, they must follow the design criteria specified in this report. One of the most important design requirements is that the structures designed by David Rosgen have an attached floodplain where the structure meets the streambank. The floodplain disperses the energy of the flow, reducing shear stress. In the vicinity of some bridges, a floodplain cannot be implemented. In such cases, culverts can be installed at the floodplain level, that pass under the bridge to help reduce shear stresses, mimicking a floodplain. Cross-Vanes and W-Weirs can be used to protect bridges and other infrastructure. Based on modeling and comparing restoration structures to a labyrinth weir, they still have an impact on higher flows. At higher than design flows, such as experienced at bridges, the structures help to reduce shear stresses. To further investigate their use as a scour countermeasure near bridges, it is recommended that a structure be installed near a bridge following this report's design criteria. This will be determined depending on available funding.

No description available.

No description available.