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<br />HYDROLOGIC ANALYSIS OF THE FLOOD <br /> <br />19 <br /> <br /> <br />FIGURE 12.-Lawn Lake about 1 week after the dam failure. showing the llI1':lount of water still remaining in the natural <br />depression forming the original lake (aerial). <br /> <br />VELOCITIES, DEPTHS, WIDTHS, AND AREAS <br /> <br />The most destructive components of the flood were <br />high shear stresses and high flow velocities. These high <br /> <br />velocities, particularly on the Roaring River and the Fall <br />River immediately below Cascade Lake dam, increased <br />the flood's capacity to erode and transport sediment, <br />resulting in severe channel erosion and transport of debris <br />and streambed material (fig. 10). No direct flow velocities <br />were available; however, average velocities, ranging from <br />3.3 ftls to 12.6 ftls computed by indirect-discharge <br />methods and based on model results, are shown in table 4. <br /> <br />the respective volumes (such as surveying and mapping <br />errors) and estimates of nonflood inflow to Lake Estes <br />also may have contributed to these differences. <br /> <br /> TABLE 4.-Peak flow data at selected cross sections <br />Distance ero.. <br />downstream Average M01Im= section <br />from Lawn ve1ocity,a depth, Top area,in <br />Lake dam, Infee~ in width, ....... <br />Inmile8 per second f." in feet f~t <br />0.66 b 8.0 b23.8 186 b2,070 <br />1.60 b11.3 b18.6 97 b1,340 <br />3.83 b 9.9 b14.0 348 b1,270 <br />6.36 3.6 9.0 927 2,980 <br />6.78 3.3 7.9 1,112 2,250 <br />6.60 4.6 10,1 328 1,560 <br />7.68 b11.2 blO.8 148 bl,170 <br />7.74 12.6 9.9 227 1,020 <br />8.78 12.1 10.6 170 910 <br />10.28 12.0 7.8 175 710 <br />11.46 7.4 6.4 336 880 <br />12.50 6.8 10.5 99 810 <br />aBased on the peak discharge profile in figure II. <br />bSevere channel erosion may have Influenced value. <br />