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<br /> <br />Figure 20.--The entrance to Aspenglen Campground downstream <br />from Cascade Lake dam through the campground area at river <br />mile 7.01. Boulders moved by the relatively wide, shallow <br />flow of water (resembling overland flow). <br /> <br />Flood-wave attenuation conti nued, with peak di scharges decreas i ng from <br />8,520 ft3/s (Site 4) at river mile 10.3 to 5,500 ft3/s (Site 6) at river mile <br />12.5. Orvi lle Johnson, located about 0.5 mi downstream from the Estes Park <br />powerplant was able to discern two flood surges. However, the surge associat- <br />ed with the failure of Cascade Lake dam rapidly attenuated, and it was not <br />noticed by eyewitnesses farther downstream. <br /> <br />Dave Thomas, observing the flood 1.2 mi upstream from Estes Park, indi- <br />cated that at first the water was running clear. Then he saw debris and the <br />floodwaters " . . '. comi ng down the ri ver. It just gradua lly began to <br />swelluthere was no wall of water." <br /> <br />As with the Roaring River, large amounts of debris affected the flow <br />considerably. Bridges and culverts became filled with debris (fig. 49), and <br />energy losses increased, resulting in high-flow resistance. These debris <br />obstructions were noted throughout this channel reach during field work after <br />the flood. Because of these obstructions and the 1 imited channel capacity of <br />the Fall River, the floodwaters went down the main street of Estes Park <br />(figs. 23 and 24). <br /> <br />The confl uence of the Fall Ri ver wi th the Big Thompson Ri ver is in Estes <br />Park (fig. 1). The Big Thompson River streamflow prior to the flood was 385 <br />ft3/s. Note that the water re-entered the main channel before flowing into <br />Lake Estes (upper right, fig. 24). The 06733000 Big Thompson River at Estes <br />Park streamflow-gaging station (Site 6) is shown at the arrival of the flood <br /> <br />43 <br />