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<br />I. <br /> <br />. <br /> <br />, <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />Figure 10, prepared by the Waterways Experiment Station, Corps of <br />Engineers, compares design criteria with both model and prototype observa- <br />tions extending over the period from the early work of Dubuat in 1786 to <br />the MclIary De.m closure study at Bonneville Hydraulic Laboratory. The <br />right hand curve of tigure 10 corresponds very nearly to the 12: 1 slope <br />curve of figure 2 and the USBR curve corresponds very nearly to the 1: 1 <br />slope curve at figure 2. The isolated cube curve is based on air t\1n11e1 <br />tests at the State University of Iowa. These test data have been evaluated <br />in terms of water overturning isolated cubical stones resting on a smooth <br />channel bottom. <br /> <br />The Bureau of Reclamation publication (20, p. 209) has a curve similar <br />to figure 10 which shows the plotting of 12 observations at riprap pertorm- <br />ance, both satistactory and failures. The slope of the eJllbankment is not <br />always given tor evaluating the ettect of slope, but all tallures plot to <br />the right at the Bureau of Reclamation curves on tigures 9 and 10. <br /> <br />The methods compared here show considerable variability in the she <br />at stone required to resist a particular velocity. This variability in <br />results obtained with different design methods, and the uncertainty as to <br />which method gives correct results, illustrates +Jie need tor research in <br />riprap design methods. <br /> <br />11-33 <br />