Browsing by Author "Johnson, Sara"
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Item Performance assessment of H Flumes under extreme approach flow conditions(St. Anthony Falls Laboratory, 2010-03) Marr, Jeff; Johnson, Sara; Busch, DennisH Flumes were designed by the Soil Conservation Service group of the U.S. Department of Agriculture and came into widespread use in the 1930s to measure runoff in small agricultural watersheds and experimental plots. Rating tables for the head-discharge relationships were prepared based on the calibration of these devices, and calibration equations were subsequently developed. The H Flume is specified to have an opening with sloping sides in the lateral and upstream direction. Laterally the opening has a 6 to 1 slope, and in the flow direction the opening has a 2 to 1 slope.Item Performance assessment of H Flumes under extreme approach flow conditions(St. Anthony Falls Laboratory, 2010-03) Marr, Jeff; Johnson, Sara; Busch, DennisH Flumes were designed by the Soil Conservation Service group of the U.S. Department of Agriculture and came into widespread use in the 1930s to measure runoff in small agricultural watersheds and experimental plots. Rating tables for the head-discharge relationships were prepared based on the calibration of these devices, and calibration equations were subsequently developed. The H Flume is specified to have an opening with sloping sides in the lateral and upstream direction. Laterally the opening has a 6 to 1 slope, and in the flow direction the opening has a 2 to 1 slope.Item Performance Assessment of Oversized Culverts to Accommodate Fish Passage(Minnesota Department of Transportation Research Services Section, 2011-08) Hansen, Brad; Johnson, Sara; Nieber, John L.; Marr, JeffIn Minnesota there is not a standard culvert design used at road crossings to improve aquatic organism or fish passage. The design process for fish passage in Minnesota is currently based on the knowledge and experience of local county, state and DNR personnel. The design methodology attempts to maintain the natural stream dimensions, pattern and profile through the culvert crossing. If designed properly aquatic organisms and fish that can make it upstream to the culvert should be able to pass through the culvert. This research was conducted to better understand the hydraulic conditions related to the practice of recessing culverts and other fish passage design elements over a range of landscapes in Minnesota. The design elements analyzed included bankfull width, slope, channel materials, side barrels and recessed culverts. Nineteen culvert sites were survey around the state. The main criterion used to evaluate performance of the culverts was the presence or absence of adequate sediment in the recessed culvert barrel. Six of the fourteen sites with recessed barrels had no sediment accumulation. A likely reason that these culverts lack sediment was increased velocities due to improper sizing relative to bankfull channel width and the accumulation of sediment in the side barrels. Wider Rosgen āCā type channels also correlated with performance issues related to culvert design.Item Physical Model Study of Marmot Dam Removal: Cofferdam Notch Location and Resulting Fluvial Responses(St. Anthony Falls Laboratory, 2007-09) Marr, Jeffrey D.G.; Hill, Craig; Johnson, Sara; Grant, Gordon; Campbell, Karen; Mohseni, OmidThis report summarizes observations made for a set of experiments conducted using the physical model of the Sandy River and Marmot Dam constructed for Portland General Electric (PGE). The experiments focused on the location of the cofferdam notch and its impact on the immediate sediment remobilization, knickpoint location and trajectory, volume of removal, and location of stranded sediment. The motivation for the study was to provide insights on how and if the position of a cofferdam notch will have an impact on how the site fails and how the reservoir sediments are remobilized. Based on early experiments with the model, PGE expressed concern that some failure scenarios resulted in abandonment of large terraces of sediment near the dam site, posing potential public safety issues. One goal of these experiments was to determine if cofferdam notch location could be positioned to minimize the volume of sediment stranded in terraces. Eight model scenarios were completed for this study. Seven of the scenarios examined a failure discharge of 2500 cfs (cubic feet per second), the minimum failure design discharge. Within these seven scenarios, we examined three notch positions; river right (north bank of river), center, and river left (south bank of river). In an eighth scenario we examined a river right notch location and failure at a high discharge of 5500 cfs. Sediment mixtures used in the model were scaled to sediment core data of the Sandy River reservoir sediment. The data and observations indicate that at the minimum design failure discharge of 2500 cfs, notch position does impact the location of cofferdam failure as well as the location of the first major knickpoint and its trajectory. The data suggest that a river left notch position minimizes the extent of stranded sediment terraces and a river right notch tends to result in larger terraces. A center notch position yielded similar results to the river right notch. At a discharge of 5500 cfs, results suggest that notch position is less important than at lower discharge rates, as the knickpoint is more or less bank to bank and is able to mobilize sediment more effectively.